Now Constant Pressure Fluid Delivery with a Syringe Pump

Harvard Apparatus, the world leader in syringe pumps, just released the NEW PHD ULTRA™ CP Syringe Pump. The first of its kind pump to infuse fluids under Constant Pressure by automatically adjusting the flow.

A Constant Pressure Syringe Pump Technology Breakthrough, the PHD ULTRA™ CP couples to virtually any commercially available pressure transducer/amplifier with a 0-10V output to deliver fluids with an applied force of up to 1,000 lbs with <±2% pressure accuracy.
The PHD ULTRA™ CP Family of Syringe Pumps feature:

• Applied forces between 75 and 1,000 lbs
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• Flexibility in connectivity with a USB serial port, RS-232 (RJ-11), RS-485 ports for daisy chaining and an I/O & TTL
• Full range of accessories – multi-syringe racks, syringe heaters, in-line heaters and coolers, microfluidic circuits, connectors, tubing, syringes and more
• Peace of mind - 2-year warranty and upgrade options available

World-renowned for accuracy and reproducibility, all PHD ULTRA™ CP syringe pumps are infuse/withdraw models and are offered in a variety of configurations to meet and exceed your research needs.

For complete specifications on these new pumps, go to www.HarvardApparatus.com or contact our Technical Support Department at techsupport@harvardapparatus.com

Harvard Apparatus
84 October Hill Road
Holliston, Massachusetts 01746 USA
Toll Free: 800-272-2775
Phone: 508-893-8999
Fax: 508-429-5732
E-mail: bioscience@harvardapparatus.com
Web: www.harvardapparatus.com

Efficient Transfection of 2 to 6 ml of Cell Suspension

The New AgilePulse^® MAX System is the latest addition to the BTX electroporation product line, offering the most advanced solution for large volume transfections by utilizing patented Pulse Agile™ technology.
This revolutionary technology delivers multiple, low to high voltage pulses with variable pulse lengths to promote greater cell membrane poration; resulting in maximum transfection efficiency with minimal damage to the cells or tissues.

This technology was used to successfully transfect dendritic cells with mRNA, as published in the Journal of Translational Medicine by Markovic et. al.¹ “The primary clinical goal of this phase 1 study was to evaluate the feasibility, safety and toxicity of an autologous MDC vaccine, electrotransfected with in vitro amplified autologous tumor-derived genomic mRNA.”
The AgilePulse MAX simplifies optimization by offering direct scale up from cuvettes to chambers, ideal for gene or drug delivery, cancer immunotherapy and protein therapeutics applications.

Features:

• Patented Pulse Agile^™ Technology
• Load Meter for Sample Monitoring
• 6 ml Large Volume Sterile Chambers

Benefits:

• Easy optimization with direct scale-up from micro - milliliter volumes
• Specially formulated Cytoporation Media for consistent and reproducible results
• Efficient transfection with maximum cell viabilities

Visit the BTX website at www.btxonline.com for more information on products, protocols or to view video tutorials for a variety of applications.

To learn more about this exciting new technology or other BTX electroporation or electrofusion products, contact:

BTX
84 October Hill Road
Holliston, Massachusetts 01746 USA
Toll Free: 800-272-2775
Phone: 508-893-8999 ext 167
Fax: 508-429-5732
E-mail: techsupport@btxonline.com
Web: www.btxonline.com

Just Published: Journal of Chromatography A

A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:

Journal of Chromatography A

http://rss.sciencedirect.com/publication/science/5248

Selected papers from the latest issue:

New theory for distribution of minimum resolution in multi-component separations with noise/detection limits

25 July 2012, 10:20:58

Publication year: 2012
Source:Journal of Chromatography A, Volume 1251
Joe M. Davis
Equations were proposed recently for computing the distribution of minimum resolution (resolution distribution) of two Gaussian peaks with equal standard deviations, when peak heights in a multi-component separation follow a statistical distribution. The computation depended on the survival function of the peak-height ratio. Previously, an equation was derived for a first-order survival function that excluded peaks with heights less than a noise/detection limit. Here, an equation is derived for a corrected survival function, under the more realistic assumption that two minimally resolved peaks are lost if the height of their shoulder is less than the noise/detection limit. First-order and corrected survival functions and resolution distributions are derived for the exponential and uniform distributions of peak heights, and a corrected survival function and resolution distribution are derived for the log-normal distribution (LND) to complement a previous first-order derivation. Large peak losses (up to 99.3% of the noise/detection limit) are considered to find significant differences between the first-order and corrected resolution distributions. For the LND and exponential distribution, the corrected resolution distribution has slightly greater density in the low-resolution region but otherwise differs little from its first-order counterpart, unless the scale parameter of the LND is small (e.g. 0.75). For the uniform peak-height distribution, the corrected resolution distribution has higher density in the high-resolution region. The first-order and corrected resolution distributions are almost the same as long as the first moment of the first-order resolution distribution is greater than 0.6. The predictions are confirmed by Monte–Carlo simulation.

Highlights

► The distribution of resolution was computed for two peaks with random heights. ► Log-normal, exponential, and uniform peak-height distributions were investigated. ► The exclusion of peaks from distributions by a noise or detection limit was examined. ► Two exclusion criteria, based on peak height and shoulder height, were used. ► Both criteria predicted similar distributions except for small peak-height ranges.

Stir frit microextraction: An approach for the determination of volatile compounds in water by headspace-gas chromatography/mass spectrometry

25 July 2012, 10:20:58

Publication year: 2012
Source:Journal of Chromatography A, Volume 1251
M. Roldán-Pijuán, M.C. Alcudia-León, R. Lucena, S. Cárdenas, M. Valcárcel
In this article, a novel extraction approach, called stir frit microextraction (SFME), is presented. The new approach combines the extractive capability of a commercial polyethylene frit (20μm of pore size) with the stirring in the same device. The proposed extraction procedure allows the determination of benzene, toluene, ethylbenzene, xylene isomers and styrene (BTEX-S) in water samples. The analytes are extracted on the frit, previously conditioned with methanol, under continuous magnetic stirring. Once the extraction is performed, the frit is transferred to a headspace vial where the volatile compounds are desorbed from the frit (90°C, 30min) in a headspace module and analyzed by gas chromatography/mass spectrometry. Headspace conditions (time and temperature) as well as extraction conditions (ionic strength, type of stirring, extraction time, stirring rate and sample volume) have been systematically evaluated. The method was characterized on the basis of its linearity, sensitivity and precision. Limits of detection were in the range from 18ng/L (o-xylene) to 65ng/L (benzene). The repeatability of the proposed method, expressed as relative standard deviation (RSD) varied between 3.8% (toluene) and 8.2% (m- and p-xylene). The recovery study carried out in different water samples provided an average recovery of 94%, which demonstrated the applicability of the stir frit microextraction for the analytical problem selected in this article.

Highlights

► Stir frit microextraction combines extraction and stirring in the same device. ► A raw polyethylene frit is employed as sorptive material. ► The proposed extraction procedure allows the determination of BTEX-S from waters. ► The limits of detection were in the nanogram per liter range with good precision.

A multi-residue method for pesticides analysis in green coffee beans using gas chromatography–negative chemical ionization mass spectrometry in selective ion monitoring mode

25 July 2012, 10:20:58

Publication year: 2012
Source:Journal of Chromatography A, Volume 1251
Ionara R. Pizzutti, Andre de Kok, Carmem Dickow Cardoso, Bárbara Reichert, Marijke de Kroon, Wouter Wind, Laís Weber Righi, Rosselei Caiel da Silva
In this study, a new gas chromatography–mass spectrometry (GC–MS) method, using the very selective negative chemical ionization (NCI) mode, was developed and applied in combination with a modified acetonitrile-based extraction method (QuEChERS) for the analysis of a large number of pesticide residues (51 pesticides, including isomers and degradation products) in green coffee beans. A previously developed integrated sample homogenization and extraction method for both pesticides and mycotoxins analysis was used. An homogeneous slurry of green milled coffee beans and water (ratio 1:4, w/w) was prepared and extracted with acetonitrile/acetic acid (1%), followed by magnesium sulfate addition for phase separation. Aliquots from this extract could be used directly for LC–MS/MS analysis of mycotoxins and LC-amenable pesticides. For GC–MS analysis, a further clean-up was necessary. C18- and PSA-bonded silica were tested as dispersive solid-phase extraction (d-SPE) sorbents, separate and as a mixture, and the best results were obtained using C18-bonded silica. For the optimal sensitivity and selectivity, GC–MS detection in the NCI-selected ion monitoring (SIM) mode had to be used to allow the fast analysis of the difficult coffee bean matrix. The validation was performed by analyzing recovery samples at three different spike concentrations, 10, 20 and 50μgkg⁻¹, with 6 replicates (n =6) at each concentration. Linearity (r ²) of calibration curves, estimated instrument and method limits of detection and limits of quantification (LOD i , LOD m , LOQ i and LOQ m , respectively), accuracy (as recovery %), precision (as RSD%) and matrix effects (%) were determined for each individual pesticide. From the 51 analytes (42 parent pesticides, 4 isomers and 5 degradation products) determined by GC–MS (NCI-SIM), approximately 76% showed average recoveries between 70–120% and 75% and RSD≤20% at the lowest spike concentration of 10μgkg⁻¹, the target method LOQ. For the spike concentrations of 20 and 50μgkg⁻¹, the recoveries and RSDs were even better. The validated LOQ m was 10, 20 and 50μgkg⁻¹ for respectively 33, 3 and 6 of the analytes studied. For five compounds, the European Union method performance requirements for the validation of a quantitative method (average recoveries between 70-120% and repeatability RSD≤20%) were not achieved and 4 problematic pesticides (captan, captafol, folpet and dicofol) could not be detected as their parent compound, but only via their degradation products. Although the matrix effect (matrix-enhanced detector response) was high for all pesticides studied, the matrix interference was minimal, due to the high selectivity obtained with the GC–NCI-MS detection. Matrix-matched calibration for applying the method in routine analysis is recommended for reliable quantitative results.

Highlights

► A selective GC–MS (NCI-SIM) method and modified QuEChERS method were developed. ► An efficient slurry method for homogenization of green coffee beans was used. ► Clean-up sorbents were tested and C18-bonded silica was optimal. ► Validation was performed at spike concentrations of 10, 20 and 50μgkg⁻¹ (n =6, at each level). ► Accuracy, precision, matrix effect, linearity, LOD and LOQ were assessed.

A new 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ionic liquid based ultrasound-assisted emulsification microextraction for the determination of organic ultraviolet filters in environmental water samples

25 July 2012, 10:20:58

Publication year: 2012
Source:Journal of Chromatography A, Volume 1251
Dandan Ge, Hian Kee Lee
A novel microextraction approach termed ionic liquid based ultrasound-assisted emulsification microextraction (IL-USAEME) combined with high-performance liquid chromatography-ultraviolet (HPLC-UV) was developed for the preconcentration and detection of organic ultraviolet (UV) filters in environmental water samples. An ionic liquid (IL) was used in place of an organic solvent as in conventional USAEME. In the study, orthogonal array designs (OAD) were employed for the optimization of the extraction parameters: type of IL, pH of the sample, extraction volume, ultrasonic time and salt concentration. In the first step, a mixed level OAD matrix, OA16 (4¹ ×2¹²) was employed for the initial optimization. Based on the results of the first step, an ultra-hydrophobic IL, 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate was chosen as the IL extractant and sample pH was set at a value of 3. Ultrasonic time, extraction volume and salt concentration were further optimized in the second step by an OA16 (4⁵) matrix. Under the latter optimized conditions, calibration curves with coefficients of estimation higher than 0.997 over the concentration range of 5 and 1000ng/ml, and the relative standard deviations for six replicates of the extraction from 2.6 to 6.6% were obtained. The limits of detection for four organic UV filters were between 0.5 and 1ng/ml. The validated technique was applied to the analysis of organic UV filters in environmental water samples.

Highlights

► Ionic liquid, [HMIM][FAP], was used as a novel extractant in USAEME. ► Orthogonal array designs were employed for optimization of extraction parameters. ► Simple, fast and efficient method with good linearity, low LODs and %RSDs.

Cloud point–dispersive μ-solid phase extraction of hydrophobic organic compounds onto highly hydrophobic core–shell Fe2O3@C magnetic nanoparticles

25 July 2012, 10:20:58

Publication year: 2012
Source:Journal of Chromatography A, Volume 1251
Dimosthenis L. Giokas, Qing Zhu, Qinmin Pan, Alberto Chisvert
A novel two-step extraction technique combining cloud point extraction (CPE) with dispersive micro-solid phase extraction (D-μ-SPE) is presented in this work for the first time. The method involves initial extraction of the target analytes by CPE in the micelles of a non-ionic surfactant medium; then highly hydrophobic polysiloxane-coated core–shell Fe2O3@C magnetic nanoparticles (MNPs) are used to retrieve the micellar phase. In that manner, the micellar phase containing the analytes is the target of the D-μ-SPE step rather than the analytes directly. MNPs are then collected by the application of an adscititious magnetic field overcoming the need for specific steps associated with CPE such as centrifugation to separate the surfactant-rich phase, refrigeration of the condensed micellar phase to reduce its viscosity or appropriate apparatus that enable direct sampling of the surfactant-rich phase. A noteworthy feature of the method is the introduction of highly oleophilic MNPs, which afford rapid and quantitative mass transfer of the surfactant phase, as opposed to other more conventional hydrophobic nanoparticles. In that manner, fast and reproducible extraction is accomplished, lending improved analytical features compared to conventional CPE, such as reduced analysis time and relative inertness to surfactant concentration and equilibration temperature. The analytes were recovered from the surface of MNPs by ultrasound-assisted back-extraction in a water-immiscible organic solvent where analytes are readily partitioned but the surfactant has limited solubility, thus minimizing its interference during chromatographic detection. As an analytical demonstration, different UV absorbing chemicals with various physico-chemical properties were used as model organic compounds for optimizing the parameters associated with this novel two-step extraction approach. The proposed method, combining two different and efficient techniques, offers satisfactory analytical features in terms of repeatability (4.5–7.5%), reproducibility (7.0–14.9%) and accuracy (88.5–97.2%). Most importantly it poses as an alternative and fast method for sample pretreatment opening new insights in surfactant-mediated extractions.

Highlights

► Cloud point extraction is combined with dispersive micro-solid phase extraction. ► Highly hydrophobic magnetic nanoparticles are used to rapidly collect the micelles. ► Cloud point extraction is applied as a microscale sample preparation method. ► The method minimizes certain limitations and simplifies the CPE procedure.

Solid-phase extraction combined with dispersive liquid–liquid microextraction, fast derivatisation and high performance liquid chromatography–tandem mass spectrometry analysis for trace determination of short-chained dodecyl alcohol ethoxylates and dodecyl alcohol in environmental water samples

25 July 2012, 10:20:58

Publication year: 2012
Source:Journal of Chromatography A, Volume 1251
Agnieszka Zgoła-Grześkowiak, Tomasz Grześkowiak
A new method was developed for preconcentration, derivatisation and analysis of short-chained dodecyl alcohol ethoxylates and dodecyl alcohol. Solid-phase extraction combined with dispersive liquid–liquid microextraction was used for preconcentration of target compounds. Several parameters were optimised including different solid phase extraction sorbents, type and volume of both extracting and dispersive solvents. As a result fast and relatively simple preconcentration method was developed. The analytes were preconcentrated 700 times with the use of small sample volume. The target compounds were derivatised before analysis with the use of newly developed procedure. The derivatisation procedure was made in vial insert and was performed at room temperature with the use of 1-naphthoyl chloride as the derivatisation agent. The developed method was used for the analysis of short-chained dodecyl alcohol ethoxylates and dodecyl alcohol in both sewage effluent from sewage treatment plants and river water samples.

Highlights

► We have developed a new isolation procedure for dodecyl alcohol and its ethoxylates. ► We have developed a new derivatisation procedure in microlitre volumes. ► We have determined target compounds in samples from sewage effluents and river water.

Optimization of solvent bar microextraction combined with gas chromatography mass spectrometry for preconcentration and determination of tramadol in biological samples

25 July 2012, 10:20:58

Publication year: 2012
Source:Journal of Chromatography A, Volume 1251
Ensieh Ghasemi
A simple, rapid and sensitive analytical method for preconcentration and determination of tramadol in different biological samples have been developed using solvent bar microextraction (SBME) combined with gas chromatography–mass spectrometry (GC–MS). The target drugs were extracted from 12ml of aqueous sample with pH 12.0 (source phase; SP) into an organic extracting solvent (n-nonanol) located inside the pores and lumen of a polypropylene hollow fiber (receiving phase; RP). In order to obtain high extraction efficiency, the effect of different variables on the extraction efficiency was studied using an experimental design. The variables of interest were the type of organic phase, pH of the source phases, ionic strength, volume of the source phase, stirring rate, extraction time and temperature. The experimental parameters of SBME were optimized using a Box–Behnken design (BBD) after a Plackett–Burman screening design. The detection limits were 0.02μgL⁻¹ with 4.5% RSD (n =5, c =10μgL⁻¹) for tramadol. Finally, the applicability of the proposed method was evaluated by extraction and determination of the drugs in different biological samples. The results indicated that SBME method has excellent clean-up and high-preconcentration factor and can be served as a simple and sensitive method for monitoring of tramadol in the biological samples.

Highlights

► SBME–GC–MS was applied for preconcentration and determination of tramadol. ► The experimental parameters were optimized using chemometric design. ► Under optimum conditions, the high preconcentration factor was obtained. ► The SBME was successfully applied for analysis of tramadol in biological samples.

Optimization for speed and sensitivity in capillary high performance liquid chromatography. The importance of column diameter in online monitoring of serotonin by microdialysis

25 July 2012, 10:20:58

Publication year: 2012
Source:Journal of Chromatography A, Volume 1251
Jing Zhang, Yansheng Liu, Andrea Jaquins-Gerstl, Zhan Shu, Adrian C. Michael, Stephen G. Weber
The speed of a separation defines the best time resolution possible in online measurements using chromatography. The desired time resolution multiplied by the flow rate of the stream of analyte being sampled defines the maximum volume of sample per injection. The best concentration sensitivity in chromatography is obtained by injecting the largest volume of sample that is consistent with achieving a satisfactory separation, and thus measurement accuracy. Taking these facts together, it is easy to understand that separation speed and concentration sensitivity are linked in this type of measurement. To address the problem of how to achieve the best sensitivity and shortest measurement time simultaneously, we have combined recent approaches to the optimization of the separation itself with an analysis of method sensitivity. This analysis leads to the column diameter becoming an important parameter in the optimization process. We use these ideas in one particular problem presented by online microdialysis sampling/liquid chromatography/electrochemical detection for measuring concentrations of serotonin in the dialysate. In this case the problem becomes the optimization of conditions to yield maximum signal for a given sample volume under the highest speed conditions with a certain required number of theoretical plates. It turns out that the observed concentration sensitivity at an electrochemical detector can be regulated by temperature, particle size, injection volume/column diameter, and void time. The theory was successfully used for optimization of neurotransmitter serotonin measurement by capillary HPLC when sampling from a microdialysis flow stream. The final conditions are: 150μm i.d., 3.1cm long columns with 1.7μm particle diameter working at a flow rate of 12μL/min, an injection volume of 500nL, and a temperature of 343K. The retention time for serotonin is 22.7s, the analysis time is about 36s (which allows for determination of 3-methoxytyramine), and the sampling time is about 0.8min with a perfusion flow rate of 0.6μL/min.

Highlights

► Our goal is system optimization for speed and concentration sensitivity. ► Concentration sensitivity depends on the injection volume. ► There is an optimum column diameter for a given injection volume. ► T, d p , V inj /d c , and t 0 regulate concentration sensitivity for a required N a . ► Serotonin (∼0.5nM) in microdialysate samples (0.5μL) in less than 30s.

Nano-scale liquid chromatography/mass spectrometry and on-the-fly orthogonal array optimization for quantification of therapeutic monoclonal antibodies and the application in preclinical analysis

25 July 2012, 10:20:58

Publication year: 2012
Source:Journal of Chromatography A, Volume 1251
Xiaotao Duan, Lipeng Dai, Shang-Chiung Chen, Joseph P. Balthasar, Jun Qu
Therapeutic monoclonal antibodies (mAbs) constitute a group of highly effective agents for treating various refractory diseases. Nonetheless it is challenging to achieve selective and accurate quantification of mAb in pharmaceutical matrices, which is required by PK studies. Liquid chromatography/mass spectrometry under selected reaction monitoring mode (LC/SRM-MS) is emerging as an attractive alternative to immunoassays because of the high specificity and multiplexing capacity it provides, but may fall short in terms of sensitivity, reliability and quantitative accuracy. Moreover, the strategy for optimization of the MS conditions for many candidates of signature peptides (SP) and the selection of the optimal SP for quantification remains elusive. In this study, we employed a suite of technical advances to overcome these difficulties, which include: (i) a nano-LC/SRM-MS approach to achieve high analytical sensitivity, (ii) a high-resolution nano-LC/LTQ/Orbitrap for confident identification of candidate peptides, (iii) an on-the-fly orthogonal array optimization (OAO) method for the high-throughput, accurate and reproducible optimization for numerous candidate peptides in a single LC/MS run without using synthesized peptides, (iv) a comprehensive evaluation of stability of candidates in matrix using the optimized SRM parameters, (v) the use of two unique SP for quantification of one mAb to gauge possible degradation/modification in biological system and thus enhancing data reliability (e.g. rejection of data if the deviation between the two SP is greater than 25%) and (vi) the utilization of purified target protein as the calibrator to eliminate the risk of severe negative biases that could occur when a synthesized peptide is used as calibrator. To show a proof of concept, this strategy is applied in the quantification of cT84.66, a chimeric, anti-CEA antibody, in preclinical mouse models. A low detection limit of the mAb down to 3.2ng/mL was achieved, which is substantially more sensitive than established immunoassay methods for anti-CEA antibodies. The quantitative method showed good linearity (within the range of 12.9ng/mL to 32.3μg/mL in plasma), accuracy and precision. Additionally, the ultra-low sample consumption (2μL plasma per preparation) permits the acquisition of an entire set of time course data from the same mouse, which represents a prominent advantage for PK study using small-animal models. The developed method enabled an accurate PK investigation of cT84.66 in mice following intravenous and subcutaneous administrations at relatively low doses over an extended period of time. The strategy employed in this study can be easily adapted to the sensitive and accurate analysis of other mAb and therapeutic proteins.

Highlights

► OAO procedure allowed for rational selection of optimal signature peptide and high-throughput method development. ► The use of nano-LC/MS enabled highly sensitive quantification of mAb in plasma. ► The use of two unique SP and protein calibrator enhanced quantitative accuracy. ► The extremely low sample consumption is desirable for small-animal models. ► The method provided superior selectivity and sensitivity over immunoassays.

Tetraazacalix[2]arene[2]triazine modified silica gel: A novel multi-interaction stationary phase for mixed-mode chromatography

25 July 2012, 10:20:58

Publication year: 2012
Source:Journal of Chromatography A, Volume 1251
Wenjie Zhao, Wenjing Wang, Hong Chang, Shiwei Cui, Kai Hu, Lijun He, Kui Lu, Jinxia Liu, Yangjie Wu, Jiang Qian, Shusheng Zhang
A novel multi-interaction and mixed-mode stationary phase based on tetraazacalix[2]arene[2]triazine modified silica (NCS) was synthesized and characterized by infrared spectra, elemental analysis and thermogravimetric analysis. Mechanism involved in the chromatographic separation is the multi-interaction including hydrophobic, π–π, hydrogen-bonding, inclusion and anion-exchange interactions. Based on these interactions, successful separation could be achieved among polycyclic aromatic hydrocarbons, aromatic position isomers, organic bases and phenols in reversed-phase chromatography. Inorganic anions were also shown to be individually separated in anion-exchange chromatography by using the same column. Moreover, the results here also demonstrated that NCS based stationary phase could effectively reduce the adverse effect of residual silanol in the separation process. Such stationary phase with characteristics of multi-interaction mechanism and mixed-mode separation is potential for the analysis of complex samples.

Highlights

► Tetraazacalix[2]arene[2]triazine was first utilized as a selector in chromatography. ► Multiple retention mechanism was involved in the chromatographic separation. ► The new material is a mixed-mode reversed-phase/anion-exchange phase. ► Tetraazacalix[2]arene[2]triazine can effectively mask the residual silanols.

Preparation and evaluation of poly(4-vinylphenylboronic acid-co-pentaerythritol triacrylate) monolithic column for capillary liquid chromatography of small molecules and proteins

25 July 2012, 10:20:58

Publication year: 2012
Source:Journal of Chromatography A, Volume 1251
Hui Huang, Zian Lin, Yao Lin, Xiaobo Sun, Yanyan Xie, Lan Zhang, Guonan Chen
A mixed-mode monolithic stationary phase was prepared for capillary liquid chromatography (cLC) by in situ copolymerization of 4-vinylphenylboronic acid (VPBA) and pentaerythritol triacrylate (PETA) in a binary porogenic solvent consisting of ethylene glycol/cyclohexanol. The monomer of VPBA functioned as ion-exchange sites, hydrophilic ligands, hydrophobic groups and affinity sites, while PETA was introduced as a hydrophilic crosslinker. The resultant monoliths with different column properties (e.g. morphology, permeability and selectivity) were optimized by adjusting the ratio of VPBA to PETA and the composition of porogenic solvent. The results showed that the selectivity of the monoliths increased with increasing content of VPBA in the polymerization mixture. A series of alkylbenzenes, amides, and anilines were used to evaluate the column performance in terms of hydrophobic, hydrophilic and cation-exchange interactions. At an optimized flow rate of 50μL/min (corresponding to 0.265mm/s), the monolith exhibited high column efficiencies of 43,000–100,000plates/m for alkylbenzenes. Good repeatability was obtained with relative standard deviation (RSD) of retention factor (k) less than 0.65% for run-to-run (n =5) and less than 2.49% for column-to-column (n =5). In addition, the poly(VPBA-co-PETA) monolithic column was applied to the separation of phenols, nucleobases, and proteins, respectively. These successful applications demonstrate the purposed monoliths are promising for cLC separation of small molecules and proteins.

Highlights

► A mixed-mode poly(VPBA-co-PETA) monolithic column is prepared via single-step in situ polymerization. ► It can be applied to the separation of a series of small molecules and proteins. ► The purposed monolith exhibits high separation ability and selectivity.

High-performance liquid chromatography enantioseparation of atropisomeric 4,4′-bipyridines on polysaccharide-type chiral stationary phases: Impact of substituents and electronic properties

25 July 2012, 10:20:58

Publication year: 2012
Source:Journal of Chromatography A, Volume 1251
Paola Peluso, Victor Mamane, Emmanuel Aubert, Sergio Cossu
The high performance liquid chromatography (HPLC) enantioseparation of eleven atropisomeric 4,4′-bipyridines was performed in the normal and polar organic phase mode using three cellulose-based chiral stationary phases (CSPs), namely Lux^® Cellulose-1, Lux^® Cellulose-2, Lux^® Cellulose-4, and two amylose-based CSPs, Chiralpak^® AD-H and Lux^® Amylose-2. n-Hexane/2-propanol mixtures and pure ethanol were employed as mobile phases. The combined use of Chiralpak^® AD-H and Lux^® Cellulose-2 allowed to enantioseparate all the considered bipyridines. Ten bipyridines were enantioseparated at the multimilligram level allowing the elution sequence determination of the enantiomers as well as their future use for the preparation of homochiral metal organic frameworks (MOFs). Moreover, the performance of the CSPs regarding the same bipyridine was different and dependent on the backbone as well as on the side chain of the polymer. The impact of substitution pattern, shape and electronic properties of the molecules on the separation behavior was investigated through the evaluation of retention factors (k), separation factors (α), resolution (R s) and molecular properties determined using density functional theory (DFT) calculations. In this regard, the substituents at the 3,3′,5,5′ positions of the 4,4′-bipyridyl rings exhibited a pivotal role on the enantioseparation.

Highlights

► Chiralpak AD-H and Lux Cellulose-2 allowed to enantioseparate 4,4′-bipyridines. ► Ten out of eleven bipyridines were enantioseparated at the multimilligram level. ► Impact of substituents and electronic properties on enantioseparation is discussed.

Calibration for Sulfur Impurities in Carbon Dioxide

The FlexStream™ computer controlled, Gas Standards Generating System dynamically blends calibration gas standards for trace sulfur compounds in food grade carbon dioxide.  Trace Source™ permeation tubes add low ppb concentrations of typical sulfur species including COS, H2S, mercaptans directly to a controlled flow of purified, beverage grade CO2 to create trace concentration calibration standards.  Residual background contamination in the CO2 matrix gas  is compensated for by using the Standard Additions Technique.  Calibration is based on the known difference in sulfur compound concentration due to the addition from the Trace Source™ permeation tubes.  A secondary dilution feature gives ppt concentrations.   Concentration is adjustable over a wide dynamic range.  Mixture concentrations are traceable to NIST through physical standards.

Trace sulfur impurities in carbon dioxide used for carbonation create “off taste” and “off odor” in beverage products.  Since these impurities occur naturally, the CO2 purity must be monitored. Effective calibration of the monitoring systems requires traceable reference standards at multiple concentrations for each of the potential contaminants.  Static mixtures containing trace concentrations of sulfur compounds are typically not stable in storage. 

For more information, please write or call:  KIN-TEK Laboratories, Inc., 504 Laurel, La Marque, TX  77568, Phone:  (409) 938-3627, Fax: (409) 938-3710, www.kin-tek.com,  email:  sales@kin-tek.com

ITP2012

ITP2012.okstate.edu Baltimore, MD, 
September 30 to October 3, 2012 
Chair: Prof. Ziad El Rassi

ITP 2012 is a completely new edition of the ITP meeting series with a wide spectrum of lectures covering many brilliant research ideas and various disciplines. The program draws world renowned speakers who discuss novel approaches in liquid phase separations, detection and sample preparation using LC, micro and nano-LC, capillary and chip-based electroseparation techniques (e.g., CZE, CIEF, CITP, MEKC, MEEKC, CEC), as well as stationary phases and coatings, nanotechnology, microfluidics, LC-MS, CE-MS, CEC-MS, and Dielectrophoresis.

This week, we are proud to feature a series of lectures on various omics, biomarker discovery, disease diagnosis and biomedical applications. DO NOT MISS the ITP event, and be a part of its rich scientific program by submitting abstracts for poster and oral presentations. Your presence at the meeting will not only inspire you with new research ideas but will also provide you with an excellent visibility to your research program among prominent scientists and colleagues from all over the world.


Featured lectures on various omics, biomarker discovery, disease diagnosis and biomedical applications

• Yoshinobu Baba, Nagoya University, Nagoya, Japan. "Nanofluidics based single biomolecule and single cell analysis for cancer diagnosis and stem cell therapy"  
• Coral Barbas, Universidad San Pablo-CEU, Madrid, Spain. "Multiplatform metabolomic strategy to study Leishmania resistance mechanisms"  
• Jonas Bergquist, Uppsala University, Uppsala,  Sweden.  "Neurochemical patterns in CNS disorders - A molecular diagnostic tool" 
• Shu-Hui Chen, National Cheng Kung University, Tainan, Taiwan. "Gold nanoparticle-based immuno probes for targeting proteomics"  
• Alejandro Cifuentes, CSIC, Madrid, Spain. "Effect of dietary polyphenols on K562 leukemia cells: A foodomics approach"  
• Rafael Davalos, Virginia Tech, Blacksburg, VA, USA.  "Isolation of cancer stem cells (CSCs) based on their dielectrophoretic signature" 
• Norman Dovichi, University of Notre Dame, Notre Dame, IN, USA . "Capillary zone electrophoresis coupled with an electrokinetically-pumped electrospray interface for applications in proteomics"  
• Ying-Sing Fung, Hong Kong University, Hong Kong. "Microfluidic chip-capillary electrophoresis devices for metabolomics applications"  
• Norberto A. Guzman, Princeton Biochemicals Inc., Princeton, NJ, USA. "Profiling of comprehensive proteomics in inflammatory diseases by immunoaffinity capillary electrophoresis"  
• Samir Hanash, Fred Hutchinson Cancer Research  Center, Seattle, WA, USA. "The wide world of proteomic  technologies for biomarker discovery"  
• Milton Hearn, Monash University, Clayton, Victoria, Australia. "Application of biomimetic molecularly imprinted polymer thin films in the electro- and liquid phase-separation of biomolecules" 
• Michael J. Heller, University of California San Diego, La Jolla, CA, USA. "Dielectrophoretic/electrophoretic device for in-situ sample preparation and PCR detection of disease biomarkers"  
• Jun Hirabayashi, National Institute of  Advanced Industrial Science and Technology, Research Center for Medical  Glycoscience, Tsukuba-Ibaraki, Japan.  "Development of lectin affinity separation technologies and their  applications to bioscience/bioindustry"  
• Cornelius Ivory, Washington State University, Pullman, WA, USA. "Concentration of low-abundance proteins from serum using microchip isotachophoresis"  
• Kyung-Jin Jang and Kahp-Yang Suh, Harvard University, Boston, MA, USA; Seoul National University, Seoul, South Korea. "Biomimetic approaches for organ on chips: neuron and kidney chip for tissue engineering and drug screening"  
• Barry Karger, Northeastern University, Barnett  Institute, Boston, MA, USA. "The critical role of the front end to the mass spectrometer for protein and proteome analysis"
• Joseph R Lakowicz, University of Maryland School of Medicine, Baltimore, MD, USA.  "Plasmon-controlled fluorescence: Applications to the biosciences" 
• Herbert Lindner, Innsbruck Medical University, Innsbruck, Austria. "CESI-MS, a promising tool for the analysis of peptides and their post-translationally modified forms in proteomic studies"  
• Craig E. Lunte, University of Kansas, Lawrence, KS, USA. "Monitoring oxidative stress using capillary electrophoresis with electrochemical and fluorescence detection"  
• Michal J. Markuszewski, Medical University of Gdańsk, Gdańsk, Poland. "Metabolite profiling in urine of cancer patients by LC-TOF-MS and LC-MS/MS" 
• Yehia Mechref, Texas Tech University, Lubbock, TX, USA. "Assessing the glycomic changes of breast cancer tissues by LC-MS"  
• Terry Phillips, NIH, Bethesda, MD, USA.  "A recycling immunoaffinity microfluidic device for assessing immune function in infants using dried blood spots"  
• Pier Giorgio Righetti, Milan Polytechnic of  Chemistry, Milano, Italy. "The silk-road, Marco Polo, the Bible and its  proteome: a detective story"  
• David C. Schwartz, University of Wisconsin-Madison, Madison, WI, USA. "Genomic claustrophobia via nanoconfinement systems"
• Govert W. Somsen, Utrecht University,  Utrecht, Netherlands. "Enhanced coverage of the anionic urine metabolome by CE-TOF-MS" 
• Miroslava Stastna, Johns Hopkins University, Baltimore, MD, USA.  "Analysis of secretome and plasma using reversed phase liquid chromatography in mass spectrometry-based pipeline for enhanced biomarker development"  
• Marina Tavares, University of Sao Paulo, Sao Paulo,  Brazil. "Urinary evaluation of amino acids and  peptides of children affected by vesicoureteral reflux" 
• Ann Van Schepdael, Catholic University of Leuven, Leuven, Belgium. "Capillary electrophoresis coupled to ESI mass spectrometry for the study of matrix metalloproteinase"
• Timothy Veenstra, SAIC Frederick, Inc., Frederick, MD, USA. "Effect of phytoestrogen genistein on human breast cancer cells" 
• Dajana Vuckovic, University of Toronto, Toronto, Ontario, Canada. "In vivo solid-phase microextraction: new tool in metabolomics"

See the Full Preliminary List of Confirmed Speakers

 Interest to be a part of the premier conference in the broad field of electro- and liquid phase-separation techniques continues to grow. As a result, the program is being expanded to include additional parallel sessions that will accommodate 130+ oral presentations. A number of openings is still available, and abstract submission for oral presentation is welcomed until the program is filled. Posters will be prominently featured in an environment that will welcome deeper discussions with colleagues from around the globe. If you have not done so, we encourage you to share your research by contributing a poster to the meeting. Poster abstracts will be accepted through September 7.

Visit: http://itp2012.okstate.edu/

Just Published: Analytica Chimica Acta

A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:

Analytica Chimica Acta
http://rss.sciencedirect.com/publication/science/5216

Selected papers from the latest issue:

Review on recent applications of the liquid waveguide capillary cell in flow based analysis techniques to enhance the sensitivity of spectroscopic detection methods

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 739
Ricardo N.M.J. Páscoa, Ildikó V. Tóth, António O.S.S. Rangel
Incorporation of long path length liquid waveguide capillary cell (LWCC or LCW) into spectrometric detection systems can increase the sensitivity of these by orders of magnitude (up to 500 times), and consequently can reduce the detection limits. The combination of the long path length spectrophotometry with flow methodologies can provide analytical solutions for various challenges in the field of environmental, biochemical and food chemistry. In this present work, the analytical applications of the long capillary cells are summarised and critically discussed. A historical overview of the cell development is given; applications in different areas are presented and grouped by analyte type. Major improvements achieved based on the use of the LWCC in the analytical characteristics (like sensitivity and detection limit) are emphasised while some of the limitations are also discussed.

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Graphical abstract Highlights

► Advances in application of liquid core waveguide capillary cell are summarised and critically discussed. ► Different flow strategies using the LWCC are presented. ► Practical advantages and limitations in application are pointed out.

Single-drop microextraction as a powerful pretreatment tool for capillary electrophoresis: A review

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 739
Zeid A. ALOthman, Mohamed Dawod, Jihye Kim, Doo Soo Chung
Single drop microextraction (SDME) is a convenient and powerful preconcentration and sample cleanup method for capillary electrophoresis (CE). In SDME, analytes are typically extracted from a sample donor solution into an acceptor drop hanging at the inlet tip of a capillary. The enriched drop is then introduced to the capillary for CE analysis. Since the volume of the acceptor drop can be as small as a few nanoliters, the consumption of solvents can be minimized and the preconcentration effect is enhanced. In addition, by covering the acceptor phase with an organic layer or by using an organic acceptor phase, inorganic ions such as salts in the sample solution can be blocked from entering the acceptor phase, providing desalting effects. Here, we describe the basic principles and instrumentation for SDME and its coupling with CE. We also review recent developments and applications of SDME-CE.

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Graphical abstract Highlights

.

► SDME is a convenient and powerful preconcentration and sample cleanup method for CE. ► SDME-CE has been applied to the analysis of target analytes in complex matrices. ► SDME-CE has been hyphenated with other on-line preconcentration techniques in CE.

Zeolite A functionalized with copper nanoparticles and graphene oxide for simultaneous electrochemical determination of dopamine and ascorbic acid

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 739
Ping He, Wei Wang, Licheng Du, Faqin Dong, Yuequan Deng, Tinghong Zhang
A novel Cu-zeolite A/graphene modified glassy carbon electrode for the simultaneous electrochemical determination of dopamine (DA) and ascorbic acid (AA) has been described. The Cu-zeolite A/graphene composites were prepared using Cu²⁺ functionalized zeolite A and graphene oxide as the precursor, and subsequently reduced by chemical agents. The composites were characterized by X-ray diffraction, Fourier transform infrared spectra and scanning electron microscopy. Based on the Cu-zeolite A/graphene-modified electrode, the potential difference between the oxidation peaks of DA and AA was over 200mV, which was adequate for the simultaneous electrochemical determination of DA and AA. Also the proposed Cu-zeolite/graphene-modified electrode showed higher electrocatalytic performance than zeolite/graphene electrode or graphene-modified electrode. The electrocatalytic oxidation currents of DA and AA were linearly related to the corresponding concentration in the range of 1.0×10⁻⁷–1.9×10⁻⁵ M for DA and 2.0×10⁻⁵–2.0×10⁻⁴ M for AA. Detection limits (<!-- no-mfc -->S/N<!-- /no-mfc -->=3) were estimated to be 4.1×10⁻⁸ M for DA and 1.1×10⁻⁵ M for AA, respectively.

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Graphical abstract Highlights

A novel Cu-zeolite A/graphene-modified glassy carbon electrode was applied in the simultaneous electrochemical determination of dopamine (DA) and ascorbic acid (AA). The potential difference between the two oxidation peaks of DA and AA were over 200mV. The electrocatalytic oxidation currents of DA were linearly related to the corresponding concentration in the range of 1.0×10⁻⁷–1.9×10⁻⁵ M.

► Cu nanoparticles doped-zeolite A/graphene (CuZEA/RGO) modified electrode was prepared. ► The composites of CuZEA/RGO were prepared via reduction of Cu²⁺ functionalized zeolite A and graphene oxide in one pot. ► The modified electrode was presented for the simultaneous determination of DA and AA. ► The proposed electrode showed a higher electrocatalytic performance.

Electro membrane extraction of biological anions with ion chromatographic analysis

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 739
Tsze Yin Tan, Chanbasha Basheer, Kai Perng Ng, Hian Kee Lee
A simple and sensitive single step electro membrane extraction (EME) procedure was demonstrated for biological organic anions with determination by ion chromatography (IC). Nitrite, adipate, oxalate, iodide, fumarate, thiocyanate and perchlorate were extracted from aqueous donor solutions, across a supported liquid membrane (SLM) consisting of methanol impregnated in the walls of a porous polypropylene membrane bag and into an alkaline aqueous acceptor solution in the lumen of the propylene envelope by the application of potential of 12V applied across the SLM. The acceptor solution was analyzed by IC. Parameters affecting the extraction performance such as type of SLM, extraction time, pH of the donor and acceptor solution, and extraction voltage were studied. The most favorable EME conditions were methanol as the SLM, extraction time of 5min, pH of acceptor and sample solutions of 12 and 4, respectively, and a voltage of 12V. Portable 12V batteries were used in the study. Under these optimized conditions, all anions had enrichment factors ranging from 3.6 to 36.2 with relative standard deviations (n =3) of between 6.6 and 17.5%. Good linearity ranging from 0.1 to 10μgmL⁻¹ with coefficients of correlation (r) of between 0.9981 and 0.9996 were obtained. The limits of detection of the EME-IC method were from 0.01 to 0.14μgmL⁻¹. The developed methodology was applied to amniotic fluid samples to evaluate the feasibility of the method for real applications.

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Graphical abstract Highlights

. Schematic of (a) battery-operated electro membrane extraction, (b) proposed extraction mechanism and (c) selected target anions.

► One-step battery-operated electro membrane extraction of anions from biological samples. ► Extraction performance was compared with liquid-phase microextraction. ► Simple and efficient analytical approach with low LODs, good linearity and repeatability.

Evaluation of DGT techniques for measuring inorganic uranium species in natural waters: Interferences, deployment time and speciation

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 739
Geraldine S.C. Turner, Graham A. Mills, Peter R. Teasdale, Jonathan L. Burnett, Sean Amos, Gary R. Fones
Three adsorbents (Chelex-100, manganese dioxide [MnO2] and Metsorb), used as binding layers with the diffusive gradient in thin film (DGT) technique, were evaluated for the measurement of inorganic uranium species in synthetic and natural waters. Uranium (U) was found to be quantitatively accumulated in solution (10–100μgL⁻¹) by all three adsorbents (uptake efficiencies of 80–99%) with elution efficiencies of 80% (Chelex-100), 84% (MnO2) and 83% (Metsorb). Consistent uptake occurred over pH (5–9), with only MnO2 affected by pH<5, and ionic strength (0.001–1molL⁻¹ NaNO3) ranges typical of natural waters, including seawater. DGT validation experiments (5 days) gave linear mass uptake over time (R ² ≥0.97) for all three adsorbents in low ionic strength solution (0.01M NaNO3). Validation experiments in artificial sea water gave linear mass uptake for Metsorb (R ² ≥0.9954) up to 12h and MnO2 (R ² ≥0.9259) up to 24h. Chelex-100 demonstrated no linear mass uptake in artificial sea water after 8h. Possible interferences were investigated with SO4 ²⁻ (0.02–200mgL⁻¹) having little affect on any of the three DGT binding layers. PO4 ³⁻ additions (5μgL⁻¹–5mgL⁻¹) interfered by forming anionic uranyl phosphate complexes that Chelex-100 was unable to accumulate, or by directly competing with the uranyl species for binding sites, as with MnO2 and the Metsorb. HCO3 ⁻ (0.1–500mgL⁻¹) additions formed anionic species which interfered with the performance of the Chelex-100 and the MnO2, and the Ca²⁺ (0.1–500mgL⁻¹) had the affect of forming labile calcium uranyl species which aided uptake of U by all three resins. DGT field deployments in sea water (Southampton Water, UK) gave a linear mass uptake of U over time with Metsorb and MnO2 (4 days). Field deployments in fresh water (River Lambourn, UK) gave linear uptake for up to 7 and 4 days for Metsorb and MnO2 respectively. Field deployment of the Metsorb-DGT samplers with various diffusive layer thicknesses (0.015–0.175cm) allowed accurate measurements of the diffusive boundary layer (DBL) and allowed DBL corrected concentrations to be determined. This DBL-corrected U concentration was half that determined when the effect of the DBL was not considered. The ability of the DGT devices to measure U isotopic ratios with no isotopic fractionation was shown by all three resins, thereby proving the usefulness of the technique for environmental monitoring purposes.

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Graphical abstract Highlights

In situ field deployment of DGT devices – manganese dioxide ( ) best suited for sea water monitoring (a) up to 7 days and Metsorb ( ) best suited for fresh water monitoring (b) of inorganic uranium species up to 7 days.

► The adsorbents Chelex-100, Metsorb and MnO2 were investigated for use with DGT. ► All three adsorbents performed well in low ionic strength solutions. ► MnO2 resin was found to be the most suitable for marine deployments. ► DGT is able to measure isotopic ratios of U down to concentrations of 0.1μgL⁻¹. ► DGT underestimated U concentrations by at least 50% if the DBL was not taken into account.

A quantitative liquid chromatography tandem mass spectrometry method for metabolomic analysis of Plasmodium falciparum lipid related metabolites

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 739
S. Vo Duy, S. Besteiro, L. Berry, C. Perigaud, F. Bressolle, H.J. Vial, I. Lefebvre-Tournier
Plasmodium falciparum is the causative agent of malaria, a deadly infectious disease for which treatments are scarce and drug-resistant parasites are now increasingly found. A comprehensive method of identifying and quantifying metabolites of this intracellular parasite could expand the arsenal of tools to understand its biology, and be used to develop new treatments against the disease. Here, we present two methods based on liquid chromatography tandem mass spectrometry for reliable measurement of water-soluble metabolites involved in phospholipid biosynthesis, as well as several other metabolites that reflect the metabolic status of the parasite including amino acids, carboxylic acids, energy-related carbohydrates, and nucleotides. A total of 35 compounds was quantified. In the first method, polar compounds were retained by hydrophilic interaction chromatography (amino column) and detected in negative mode using succinic acid-¹³C4 and fluorovaline as internal standards. In the second method, separations were carried out using reverse phase (C18) ion-pair liquid chromatography, with heptafluorobutyric acid as a volatile ion pairing reagent in positive detection mode, using d9-choline and 4-aminobutanol as internal standards. Standard curves were performed in P. falciparum-infected and uninfected red blood cells using standard addition method (r ² >0.99). The intra- and inter-day accuracy and precision as well as the extraction recovery of each compound were determined. The lower limit of quantitation varied from 50pmol to 100fmol/3×10⁷ cells. These methods were validated and successfully applied to determine intracellular concentrations of metabolites from uninfected host RBCs and isolated Plasmodium parasites.

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Graphical abstract Highlights

► Plasmodium falciparum is the causative agent of malaria. ► Two analytical techniques using LC/MS/MS developed. ► 35 compounds were quantified. ► The methods were validated and applied to determine intracellular concentrations of metabolites.

A strategy for efficient discovery of new natural compounds by integrating orthogonal column chromatography and liquid chromatography/mass spectrometry analysis: Its application in Panax ginseng, Panax quinquefolium and Panax notoginseng to characterize 437 potential new ginsenosides

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 739
Wen-zhi Yang, Min Ye, Xue Qiao, Chun-fang Liu, Wen-juan Miao, Tao Bo, Hai-yan Tao, De-an Guo
To discover new natural compounds from herbal medicines tends to be more and more difficult. In this paper, a strategy integrating orthogonal column chromatography and liquid chromatography/mass spectrometry (LC/MS) analysis was proposed, and was applied for rapid discovery of new ginsenosides from Panax ginseng (PG), Panax quinquefolium (PQ), and Panax notoginseng (PN). The ginsenosides extracts were fractionated by MCI gel×silica gel orthogonal column chromatography. The fractions were then separated on a C18 HPLC column, eluted with a three-component mobile phase (CH3CN/CH3OH/3mM CH3COONH4 H2O), and detected by electrospray ionization tandem mass spectrometry. The structures of unknown ginsenosides were elucidated by analyzing negative and positive ion mass spectra, which provided complementary information on the sapogenins and oligosaccharide chains, respectively. A total of 623 comprising 437 potential new ginsenosides were characterized from the ethanol extracts of PG, PQ and PN. New acylations, diversified saccharide chains and C-17 side chains constituted novelty of the newly identified ginsenosides. An interpretation guideline was proposed for structural characterization of unknown ginsenosides by LC/MS. To confirm reliability of this strategy, two targeted unknown trace ginsenosides were obtained in pure form by LC/MS-guided isolation. Based on extensive NMR spectroscopic analysis and other techniques, they were identified as 3-O-[6-O-(E)-butenoyl-β-d-glucopyranosyl(1,2)-β-d-glucopyranosyl]-20(S)-protopanaxadiol-20-O-β-d-glucopyranosyl(1,6)-β-d-glucopyranoside (named ginsenoside IV) and 3-O-β-d-glucopyranosyl(1,2)-β-d-glucopyranosyl-3β,12β,20(S),24(R)-tetra hydroxy-dammar-25-ene-20-O-β-d-glucopyranosyl(1,6)-β-d-glucopyranoside (ginsenoside V), respectively. The fully established structures were consistent with the MS-oriented structural elucidation. This study expanded our understanding on ginsenosides of Panax species, and the proposed strategy was proved efficient and reliable in the discovery of new minor compounds from herbal extracts.

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Graphical abstract Highlights

► Orthogonal MCI and silica gel separation achieved enrichment of minor ginsenosides. ► LC–(±)ESI-MS ⁿ analysis offered complementary structure information of ginsenosides. ► 623 ginsenosides including 437 new ones were identified from three Panax species. ► LC/MS guided isolation of P. ginseng yielded two new ginsenosides. ► NMR analysis of two new ginsenosides was consistent with LC/MS analysis.

De novo analysis of electron impact mass spectra using fragmentation trees

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 739
Franziska Hufsky, Martin Rempt, Florian Rasche, Georg Pohnert, Sebastian Böcker
The automated fragmentation analysis of high resolution EI mass spectra based on a fragmentation tree algorithm is introduced. Fragmentation trees are constructed from EI spectra by automated signal extraction and evaluation. These trees explain relevant fragmentation reactions and assign molecular formulas to fragments. The method enables the identification of the molecular ion and the molecular formula of a metabolite if the molecular ion is present in the spectrum. These identifications are independent of existing library knowledge and, thus, support assignment and structural elucidation of unknown compounds. The method works even if the molecular ion is of very low abundance or hidden under contaminants with higher masses. We apply the algorithm to a selection of 50 derivatized and underivatized metabolites and demonstrate that in 78% of cases the molecular ion can be correctly assigned. The automatically constructed fragmentation trees correspond very well to published mechanisms and allow the assignment of specific relevant fragments and fragmentation pathways even in the most complex EI-spectra in our dataset. This method will be very helpful in the automated analysis of metabolites that are not included in common libraries and it thus has the potential to support the explorative character of metabolomics studies.

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Graphical abstract Highlights

► We present a method for de novo analysis of accurate mass EI mass spectra of small molecules. ► This method identifies the molecular ion and thus the molecular formula where the molecular ion is present in the spectrum. ► Fragmentation trees are constructed by automated signal extraction and evaluation. ► These trees explain relevant fragmentation reactions. ► This method will be very helpful in the automated analysis of unknown metabolites.

Development of an automatic multi-channel ink-jet ejection chemiluminescence system and its application to the determination of horseradish peroxidase

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 739
Fengming Chen, Zhen Lin, Yongzan Zheng, Hulie Zeng, Hizuru Nakajima, Katsumi Uchiyama, Jin-Ming Lin
In this work, an automatic multi-channel ink-jet for chemiluminescence (CL) analysis was developed. The four-channel ink-jet device was controlled by a home-made circuit. Differing from the classic flow injection CL, the whole procedure for CL analysis was automatically completed on a hydrophobic glass side. CL reaction of luminal and hydrogen peroxide for the determination of horseradish peroxidase (HRP) was selected as an application to automatic CL analysis platform. All solutions delivered by different channels were precisely ejected to the same position of the glass slide for the CL analysis. The consumption of reaction solution was reduced to nanoliter level. The whole CL analysis could be completed in less than 4min, which was benefited from the prompt solution mixing in small size of droplet. The CL intensity increased linearly with HRP concentration in the range from 0.01 to 0.5μgmL⁻¹. The limit of detection (LOD) (S/N=3) was 0.005μgmL⁻¹. Finally, the automatic CL system could also be used for the detection of HRP in HRP–protein conjugates, which showed its practical application in immunoassay.

Graphical abstract

Graphical abstract Highlights

An automatic multi-channel ink-jet ejection chemiluminescence system.

► Automatic multi-channel ink-jet ejection chemiluminescence. ► Determination of horseradish peroxidase. ► Horseradish peroxidase–protein conjugates.

Detecting solution pH changes using poly (N-isopropylacrylamide)-co-acrylic acid microgel-based etalon modified quartz crystal microbalances

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 739
Kai C.C. Johnson, Francisco Mendez, Michael J. Serpe
Poly (N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc) microgel-based etalons have been shown to have visible color and unique spectral properties, which both depend on solution temperature and pH. In this investigation, pNIPAm-co-AAc microgel-based etalons were fabricated on the Au electrode of a quartz crystal microbalance (QCM), and the resonant frequency of the QCM monitored as a function of temperature, at pH 3.0. Furthermore, the resonant frequency at either pH 3.0 or 7.0 was monitored while keeping the solution temperature constant at various temperatures. In all cases, when the solution temperature was below the collapse transition for the microgels (∼32°C), the resonant frequency at pH 3.0 was lower than at pH 7.0, which we attribute to the film transitioning from a deswollen to swollen state, respectively. It was observed that the magnitude of the resonant frequency change increased as the solution temperature approached the collapse temperature for the microgels. The overall sensitivity to pH was determined to be 1.3×10⁻⁸ M [H⁺]Hz⁻¹ and a theoretical detection limit of 390nM was obtained. This sensitivity will be exploited further for future biosensing applications.

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Graphical abstract Highlights

► Color tunable materials on a QCM crystal can detect solution pH changes. ► Sensitivity of 1.3×10⁻⁸ M [H⁺]Hz⁻¹ is achieved over a 2pH unit range. ► Detection limit of 390nM [H⁺] was realized.

A sensitive microextraction by packed sorbent-based methodology combined with ultra-high pressure liquid chromatography as a powerful technique for analysis of biologically active flavonols in wines

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 739
Catarina L. Silva, João L. Gonçalves, José S. Câmara
A new approach based on microextraction by packed sorbent (MEPS) and reversed-phase high-throughput ultra high pressure liquid chromatography (UHPLC) method that uses a gradient elution and diode array detection to quantitate three biologically active flavonols in wines, myricetin, quercetin, and kaempferol, is described. In addition to performing routine experiments to establish the validity of the assay to internationally accepted criteria (selectivity, linearity, sensitivity, precision, accuracy), experiments are included to assess the effect of the important experimental parameters such as the type of sorbent material (C2, C8, C18, SIL, and C8/SCX), number of extraction cycles (extract-discard), elution volume, sample volume, and ethanol content, on the MEPS performance. The optimal conditions of MEPS extraction were obtained using C8 sorbent and small sample volumes (250μL) in five extraction cycle and in a short time period (about 5min for the entire sample preparation step). Under optimized conditions, excellent linearity ( R values 2 > 0.9963 ) , limits of detection of 0.006μgmL⁻¹ (quercetin) to 0.013μgmL⁻¹ (myricetin) and precision within 0.5–3.1% were observed for the target flavonols. The average recoveries of myricetin, quercetin and kaempferol for real samples were 83.0–97.7% with relative standard deviation (RSD, %) lower than 1.6%. The results obtained showed that the most abundant flavonol in the analyzed samples was myricetin (5.8±3.7μgmL⁻¹). Quercetin (0.97±0.41μgmL⁻¹) and kaempferol (0.66±0.24μgmL⁻¹) were found in a lower concentration. The optimized MEPSC8 method was compared with a reverse-phase solid-phase extraction (SPE) procedure using as sorbent a macroporous copolymer made from a balanced ratio of two monomers, the lipophilic divinylbenzene and the hydrophilic N-vinylpyrrolidone (Oasis HLB) were used as reference. MEPSC8 approach offers an attractive alternative for analysis of flavonols in wines, providing a number of advantages including highest extraction efficiency (from 85.9±0.9% to 92.1±0.5%) in the shortest extraction time with low solvent consumption, fast sample throughput, more environmentally friendly and easy to perform.

Graphical abstract

Graphical abstract Highlights

► An innovative methodology to pre-concentrate bioactive flavonols, MEPS. ► Rapid screening for analysis of biological active flavonols in wines. ► MEPS reduced the sample volume and the time necessary for the analysis. ► Limits the consumption of organic solvents thus also reducing the testing cost. ► Good results were obtained in terms of selectivity, precision, sensitivity and accuracy.

A data treatment method for detecting fluorescence anisotropy peaks in capillary electropherograms

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 739
Ryan A. Picou, Indu Kheterpal, S. Douglass Gilman
A data treatment method is presented to detect fluorescence anisotropy (FA) peaks in capillary electrophoresis electropherograms. The data treatment method converts plots of fluorescence anisotropy vs. time that contain no peaks that are distinguishable from the noise of the anisotropy background into plots that show distinct fluorescence anisotropy peaks. The method was demonstrated using laser-induced fluorescence anisotropy data from individual Aβ (1–42) aggregates separated using capillary electrophoresis. Applying this data treatment method enabled the detection of anisotropy peaks for individual Aβ aggregate fluorescence peaks that were not observed prior to the data treatment method. The data treatment method is not specifically designed for Aβ aggregate analysis or capillary electrophoresis, and it should be applicable to other applications and other separation methods with FA detection.

Graphical abstract

Graphical abstract Highlights

► We explain the absence of fluorescence anisotropy peaks for capillary separations. ► We developed a method to visualize fluorescence anisotropy peaks for separations. ► This method was applied to a separation of amyloid beta peptide aggregates.

Review of recent advances in the preparation of organic polymer monoliths for liquid chromatography of large molecules

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 738
R. Dario Arrua, Mohammad Talebi, Tim J. Causon, Emily F. Hilder
In recent years the use of monolithic polymers in separation science has greatly increased due to the advantages these materials present over particle-based stationary phases, such as their relative ease of preparation and good permeability. For these reasons, these materials present high potential as stationary phases for the separation and purification of large molecules such as proteins, peptides, nucleic acids and cells. An example of this is the wide range of commercial available polymer-based monolithic columns now present in the market. This review summarizes recent developments in the synthesis of monolithic polymers for separation science, such as the incorporation of nanostructures in the polymeric scaffold as well as the preparation of hybrid structures. The different methods used in the surface functionalization of monolithic columns are also reviewed. Finally, we critically discuss the recent applications of this column technology in the separation of large molecules under different chromatographic mode.

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Graphical abstract Highlights

► This review summarizes recent developments in the synthesis of polymer monoliths. ► Alternative preparation methods still remain an important area of research. ► The application of monoliths in the separation of large molecules is discussed. ► The use of polymer monoliths in the separation of real samples is still needed.

Microextraction techniques in the analysis of food flavor compounds: A review

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 738
Henryk H. Jeleń, Małgorzata Majcher, Mariusz Dziadas
Food flavor compounds due to the complexity of food as a matrix, and usually their very low concentrations in a product, as well as their low odor thresholds, create a challenge in their extraction, separation and quantitation. Food flavor volatiles represent compounds of different polarity, volatility and chemical character, which determine method of extraction for their isolation from food. Microextraction techniques, mainly SPME and SBSE have been used for food flavor compounds analysis for two decades. Microextraction methods other than SPME and SBSE are seldom used despite their analytical potential. The review discusses the nature of food flavor compounds, and different approaches to food flavor analysis. It summarizes the use of microextraction methods in food flavor compounds analysis based on papers published in the last 5years, and discusses the potential of microextraction methods in this field.

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► Microextraction methods in food flavors analysis based on 2006–2011 published papers discussed. ► SPME, SBSE, LPME methods as dominating summarized in detail. ► Potential of other, less popular in this field microextraction methods pronounced.

Mesoporous carbon amperometric glucose sensors using inexpensive, commercial methacrylate-based binders

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 738
Mingzhi Dai, Stephanie Maxwell, Bryan D. Vogt, Jeffrey T. La Belle
Two ordered, soft-templated mesoporous carbon powders with cubic and hexagonal framework structure and four different commercial, low cost methacrylate-based polymer binders with widely varying physical properties are investigated as screen printed electrodes for glucose sensors using glucose oxidase and ferricyanide as the mediator. Both the chemistry and concentration of the binder in the electrode formulation can significantly impact the performance. Poly(hydroxybutyl methacrylate) as the binder provides hydrophilicity to enable transport of species in the aqueous phase to the carbon surface, but yet is sufficiently hydrophobic to provide mechanical robustness to the sensor. The current from the mesoporous carbon electrodes can be more than an order of magnitude greater than for a commercial printed carbon electrode (Zensor) with improved sensitivity for model glucose solutions. Even when applying these sensors to rabbit whole blood, the performance of these glucose sensors compares favorably to a standard commercial glucose meter with the lower detection limit of the mesoporous electrode being approximately 20mgdL⁻¹ despite the lack of a separation membrane to prevent non-specific events; these results suggest that the small pore sizes and high surface areas associated with ordered mesoporous carbons may effectively decrease some non-specific inferences for electrochemical sensing.

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► We prepared screen printed glucose sensor with two different mesoporous carbons. ► We investigated low cost, fluorine-free methacrylate-based as polymer binders. ► Cubic structure carbon provided higher signal than hexagonal structure carbon. ► Hydrophilicity of the binder greatly impacted the performance of the sensor. ► The best sensor accurately measured glucose level in rabbit blood.

Sensitive electrochemical sensor of tryptophan based on Ag@C core–shell nanocomposite modified glassy carbon electrode

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 738
Shuxian Mao, Weifeng Li, Yumei Long, Yifeng Tu, Anping Deng
We here reported a simple electrochemical method for the detection of tryptophan (Trp) based on the Ag@C modified glassy carbon (Ag@C/GC) electrode. The Ag@C core–shell structured nanoparticles were synthesized using one-pot hydrothermal method and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier transform-infrared spectroscopy (FTIR). The electrochemical behaviors of Trp on Ag@C/GC electrode were investigated and exhibited a direct electrochemical process. The favorable electrochemical properties of Ag@C/GC electrode were attributed to the synergistic effect of the Ag core and carbon shell. The carbon shell cannot only protect Ag core but also contribute to the enhanced substrate accessibility and Trp-substrate interactions, while nano-Ag core can display good electrocatalytic activity to Trp at the same time. Under the optimum experimental conditions the oxidation peak current was linearly dependent on the Trp concentration in the range of 1.0×10⁻⁷ to 1.0×10⁻⁴ M with a detection limit of 4.0×10⁻⁸ M (S/N=3). In addition, the proposed electrode was applied for the determination of Trp concentration in real samples and satisfactory results were obtained. The technique offers enhanced sensitivity and may trigger the possibilities of the Ag@C nanocomposite towards diverse applications in biosensor and electroanalysis.

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Ag@C and Colloidal carbon sphere modified glassy carbon electrodes were prepared. It was clear that the Ag@C/GCE exhibited enhanced electrocatalytic activity towards Trp, which could result from the synergistic effect between Ag core and carbon shell. The Ag@C/GCE showed excellent analytical properties in the determination of Trp.

► The electrochemical behavior of Ag@C core–shell nanocomposite was firstly proposed. ► Ag@C/GC electrode exhibited favorable electrocatalytic properties towards Trp. ► The good electrocatalysis was due to the synergistic effect of Ag-core and C-shell. ► The Ag@C/GC electrode displayed excellent analytical properties in determining Trp.

Electrodes with extremely high hydrogen overvoltages as substrate electrodes for stripping analysis based on bismuth-coated electrodes

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 738
Ye Tian, Lianzhe Hu, Shuang Han, Yali Yuan, Jianguo Wang, Guobao Xu
Hydrogen evolution bothers stripping analysis significantly. Dioctyl phthalate-based carbon paste electrode exhibits extremely wide cathodic potential window. It is explored as a powerful substrate electrode to solve the problem of hydrogen evolution and further improve reproducibility for stripping analysis using bismuth-coated electrodes for the first time. It was successfully applied to the simultaneous determination of Zn²⁺, Cd²⁺, and Pb²⁺. Linear responses are obtained for Zn²⁺ in the range of 10–100μgL⁻¹ and for Pb²⁺ and Cd²⁺ in the range of 5–100μgL⁻¹. The detection limits for Zn²⁺, Cd²⁺, and Pb²⁺ are 0.1μgL⁻¹, 0.22μgL⁻¹ and 0.44μgL⁻¹, respectively. The method has been successfully applied to the determination of Zn²⁺, Cd²⁺, and Pb²⁺ in waste water samples. The detection strategy based on the combination of dioctyl phthalate-based carbon paste electrode and bismuth-coated electrodes holds great promise for stripping analysis.

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► Dioctyl phthalate-based CPE has extremely wide cathodic potential range. ► It has been used for bismuth-based stripping analysis for the first time. ► It can effectively avoid hydrogen evolution and improve reproducibility. ► It is suitable for detecting more active metals such as zinc. ► It is a powerful platform for bismuth-based electrochemical stripping analysis.

Fabrication of a sensor chip containing Au and Ag electrodes and its application for sensitive Hg(II) determination using chronocoulometry

24 July 2012, 08:10:19

Publication year: 2012
Source:Analytica Chimica Acta, Volume 738
Chaogui Chen, Yan Du, Jing Li, Xiurong Yang, Erkang Wang
In this work, we explored a novel fabrication method to construct Au and Ag electrodes on chip, utilizing the different solubility of gold and silver in different etching solutions. KI-I2 etching solution and 50% HNO3 were chosen to dissolve the metal layers alternatively. Planar electrodes with gold and silver could be simultaneously and accurately patterned on chip using photolithographic technique. The as-prepared electrode could be directly served as integrated three-electrode system for electrochemical measurement. Based on it, a sensing strategy has been carried out using home-made electrochemical sensing (ECS) chip, which depended on the competition of double strand DNA and Hg(II)-mediated T–T base pairs (T-Hg(II)-T). Actually, a mercury specific oligonucleotide (MSO) was immobilized onto the thus-fabricated gold working electrode and employed as the sensing element. Chronocoulometry (CC) was chosen to monitor the differences of surface charge volume and quantify the concentrations of Hg(II) ions with a low detection limit down to 1nM. Therefore, a facile method to fabricate Au and Ag electrodes has been demonstrated to simplify the production of ECS chip. The ECS chip was finally used for constructing an effective sensing platform for sensitive Hg(II) determination, which held promising potential for designing ECS chip in lab-on-a-chip device or point-of-care diagnosis.

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In this work, we explored a novel method to fabricate multi-metallic planar electrodes and constructed electrochemical sensing (ECS) chip for Hg(II) determination. Chronocoulometry was carried out to measure the differences of surface charge volume owing to specific activity of T-Hg(II)-T formation competed with double strand DNA. The facile fabrication of multi-planar electrodes and sensing platform endowed the ECS chip with great promise in environmental monitoring.

► A novel fabrication method was explored to prepare multi-metallic planar electrodes. ► Electrochemical sensing (ECS) chip has been constructed for Hg(II) analysis. ► Sensing strategy based on T-Hg(II)-T formation competed with dsDNA has been built. ► Chronocoulometry (CC) was carried out to measure the differences of surface charge. ► It resulted in a high sensitive, high selective Hg(II) determination in practical samples.