Cheminert® C52 Integrated HPLC Injector

VICI Valco’s new Cheminert C52 Series Injector presents our first integrated motor/valve assembly designed specifically to be built into an OEM system.

Using the well-proven Cheminert HPLC injector design and the 24 volt motor from our popular microelectric actuators, the C52 needs only to be connected to the instrument’s power supply. Control is simplified to require a single contact closure; the injector’s position is determined by whether the closure is held high or low. There’s even an easy way for the instrument to confirm the valve’s position by sensing the output from a built-in sensor.

All these features are built into a compact and lightweight package, available in 4, 6, 8, and 10 port configurations, stainless or PEEK. The C52 can simplify instrument designs, trim costs, and minimize time to market.

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:

Capillary electrophoresis methods for the analysis of antimalarials. Part I. Chiral separation methods

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
N’Cho Christophe Amin, Marie-Dominique Blanchin, Michèle Aké, Huguette Fabre
This paper presents an overview on the current status of enantiomeric and diastereomeric separations of chiral antimalarials and derivatives by capillary electrophoresis (CE). The wide variety of chiral selectors which have been employed to resolve successfully antimalarial enantiomers: oligosaccharides (cyclodextrins, oligomaltodextrins), neutral (amylose, dextrin and dextran) and charged (chondroitin sulfate, heparin, dextran sulfate) polysaccharides and proteins are reviewed. Cyclodextrins were the most employed. Chiral additives added to the background electrolyte often facilitated separations of quinine/quinidine and cinchonine/cinchonidine diastereomers. However, in a few cases, using micellar electrokinetic capillary chromatography or non aqueous CE, resolution of diastereomers could be achieved without additives. Quantitative applications of CE to the quality control of antimalarial drugs and their analysis in biological and food matrices are presented.

Highlights

► Exhaustive review of chiral capillary electrophoresis (CE) methods for antimalarials. ► Chiral selectors for enantiomeric and diastereomeric separations in CE. ► Quantitative applications.

Novel software-based method to classify structurally similar compounds combined with high performance liquid chromatography–quadrupole time of flight mass spectrometry to identify complex components of herbal medicines

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Qi-Yuan Shan, Gang Cao, Hao Cai, Xiao-Dong Cong, Bao-Chang Cai
The components of herbal medicines (HMs) are usually extremely complex, belonging to hundreds of compound classes with diverse chemical and physical properties. Full characterization of HMs is hugely important in order to identify the individual chemical constituents and provide a first step toward determining which components are responsible for the therapeutic effects of a particular medical plant. In this study, a novel software-based approach was developed to classify structurally similar compounds, and this was combined with high performance liquid chromatography/quadrupole time-of-flight mass spectrometry (HPLC–QTOF-MS) to identify the individual components in an extract of Mentha haplocalyx. A total of 33 compounds were tentatively identified in samples of M. haplocalyx extract, including 9 new minor constituents reported for the first time. Semi-quantitative analysis of the extract sample was also carried out. Software validation and robustness tests were performed. The results of this study demonstrate the enormous potential of this strategy, using classification based on structural similarity together with HPLC–QTOF-MS, for the identification and quantification of complex components in HMs and related products.

Highlights

► A novel software-based method is developed to analyze herbal medicines. ► The method is based on structurally similar classification of compounds. ► 33 compounds were tentatively identified in samples of Mentha haplocalyx extract. ► Including 9 new minor constituents were reported for the first time.

Superficially porous silica particles with wide pores for biomacromolecular separations

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Brian M. Wagner, Stephanie A. Schuster, Barry E. Boyes, Joseph J. Kirkland
Since 2006, columns of superficially porous particles (SPPs), often called Fused-core^®, porous–shell or core–shell particles, have had serious impact on HPLC separations. These particles have pore diameters of about 100Å designed for separating small molecules. More recently, SPPs with 160–200Å pore diameter have been made available for separating peptides and small proteins. This report describes the effects of fused-core particle size, pore size, shell thickness and ligand type for the rapid, efficient separation of larger molecules such as intact proteins and other biomacromolecules up to at least 400kDa. Optimization of these parameters resulted in particles that show no restricted diffusion that would compromise separating efficiency for large biomolecules. The thin porous shell provides excellent mass transfer (kinetics) for these large molecules, resulting in superior separations compared to conventional totally porous particles. Sample loading capacity can be adjusted to allow good detection sensitivity for minor components in a complex mixture. Strong particle strength ensures the loading of stable, high-efficiency columns. Stationary phases with different alkyl ligands were tested to provide data on retention, column efficiency and peak shapes for proteins. The development of these new wide-pore fused-core particles now allows the HPLC separation of a wide range of molecules of different sizes with advantages of the SPP configuration.

Highlights

► New 400Å pore size particles separate large proteins without restricted diffusion. ► Particles with larger surface areas allow greater sample mass loading. ► Particles with thinner shells show higher efficiency for proteins. ► New wide-pore superficially porous particles demonstrate excellent stability. ► Particles with C4 and C8 stationary phases appear superior for some protein separations.

Evaluation of hydrophilic interaction chromatography (HILIC) versus C18 reversed-phase chromatography for targeted quantification of peptides by mass spectrometry

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Romain Simon, Quentin Enjalbert, Jordane Biarc, Jérôme Lemoine, Arnaud Salvador
Hydrophilic-interaction liquid chromatography (HILIC) is a widely used technique for small polar molecule analysis and offers the advantage of improved sensitivity in mass spectrometry. Although HILIC is today frequently employed as an orthogonal fractionation method for peptides during the proteomic discovery phase, it is still seldom considered for quantification. In this study, the performances in terms of peak capacity and sensitivity of 3 HILIC columns were compared to traditional reversed phase liquid C18 column in the context of targeted quantification of proteotypic peptides using selected reaction monitoring mode (SRM). The results showed that the maximum sensitivity in HILIC chromatography was achieved by using an amide column without salt buffer and that the signal increased compared to classic reversed phase chromatography. However, the intensity improvement is quite low compared to the one obtained for small molecules. This is due on one hand to a higher matrix effect in HILIC and on the other hand to a change of charge states of peptides in organic solvent (doubly charged to monocharged). The doubly charged ions can be more readily dissociated than singly charged ions, making them ideal for SRM peptide quantification. As a result “supercharging” reagents are added to the mobile phase to shift from predominant singly charged ions to the more favorable doubly charged species. Using such optimized conditions, peptide signal is improved by a factor of between two and ten for 88% of the peptides of the 81 peptides investigated.

Highlights

► Gain in sensitivity for peptide quantitation in HILIC by LC–MS was evaluated for the first time. ► HILIC mobile phases promote monocharged peptides. ► With supercharging reagents sensitivity was enhanced by a factor 2–10.

An improved high performance liquid chromatography-fluorescence detection method for the analysis of major phenolic compounds in cigarette smoke and smokeless tobacco products

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Jingcun Wu, William S. Rickert, Andrew Masters
An improved HPLC method has been developed for the determination of major phenolic compounds in cigarette smoke. A novel reversed phase column with a pentafluorophenylpropyl (PFP) ligand in the stationary phase was chosen to separate the positional isomers (p-, m-, and o-cresols). Methanol instead of acetonitrile was used as the organic mobile phase component to improve the separation of the isomers and cope with the crisis of global acetonitrile shortage in 2009. A shorter analytical column with smaller particle size was used to further increase separation efficiency and reduces solvent consumption. These improvements have led to a new HPLC method that is simpler and faster than the GC–MS method and more sensitive, selective and efficient than the widely used traditional HPLC method. The limit of detection (LOD) and limit of quantification (LOQ) of this method are at the ng/mL level for most of the phenols with good linearity (R ² ≥0.999) and precision (RSD<15%). The method has been validated using reference tobacco products. The mainstream and sidestream cigarette smoke yields of phenolic compounds obtained by this method are comparable to those obtained by traditional HPLC method with the advantage that p-, m-, and o-cresols can be determined and reported separately by the new method. The method can also be applied for analysis of phenols in smokeless tobacco product.

Highlights

► The HPLC method for phenols analysis in tobacco smoke was improved significantly. ► Cresol isomers were separated for the first time by a HPLC method. ► Using methanol in mobile phases, this method cut solvent cost for phenols analyses. ► A shorter column was used to enhance separation and reduce analytical cost. ► The method was also used for phenols analysis in smokeless tobacco products.

Multicomponent adsorption of monoclonal antibodies on macroporous and polymer grafted cation exchangers

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Ernie X. Perez-Almodovar, Yige Wu, Giorgio Carta
We compare the rates of adsorption of two monoclonal antibodies (mAbs) with different adsorption properties on the cation exchangers UNOsphere™ S and Nuvia™ S. The former contains large open pores while the latter is based on a backbone matrix similar to UNOsphere™ S but also contains grafted charged polymers. Both single component and two-component adsorption are considered. Adsorption capacity and rates are much higher for Nuvia™ S indicating that protein interactions with the charged grafted polymers facilitate both binding and diffusional transport. Intraparticle concentration profiles obtained by confocal microscopy show sharp fronts for UNOsphere™ S but diffuse profiles for Nuvia™ S. Transport is thus controlled by pore diffusion for UNOsphere™ S but is described by a single file diffusion (SFD) mechanism for Nuvia™ S. As a result, single and two-component adsorption occur at similar rates for UNOsphere™ S independent of the direction for transport. For Nuvia™ S, however, transport is very fast for single or two-component co-adsorption but very slow when counter diffusion of the two mAbs takes place within the particles. The transport models developed in this work allow a prediction of separation performance for overloaded conditions typical of process scale applications.

Highlights

► Single and multiple mAbs adsorption in macroporous resins is pore diffusion controlled. ► Single and multiple mAbs adsorption in grafted resins is solid diffusion controlled. ► Adsorption rates depend on composition for polymer-grafted resins. ► Single file diffusion model predicts adsorption kinetics in grafted resins.

High-resolution separations of tryptic digest mixtures using core–shell particulate columns operated at 1200bar

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Jelle De Vos, Catherine Stassen, Axel Vaast, Gert Desmet, Sebastiaan Eeltink
Combining two recent advances in instrumentation and column technology (ultra-high-pressure LC instruments and core–shell particles), the current peak-capacity generation limits in one-dimensional LC have been explored for the case of tryptic digest separations. To operate as close as possible to the Knox and Saleem limit of the particles, and hence to operate the 2.6μm core–shell particles at their kinetic optimum, the separations were conducted in a coupled column systems at 1200bar. Using coupled columns with a total length of 450mm at 1200bar and applying 40 and 120min gradients (t G /t 0 =17 and 52, respectively), peak capacities of n c =480 and 760 were measured. The kinetic performance was further improved by coupling six 150mm long columns and applying 1200bar, yielding a flow rate close to the optimum of the van Deemter curve while scaling the gradient volume. At t G /t 0 =52 a peptide separation yielding a peak capacity of 1360 was achieved, applying a 480min gradient. The observed increase of peak capacity with column length agrees well with the theoretical expectations based on the linear solvent strength (LSS) model.

Highlights

► High-resolution peptide separations were obtained with 2.6μm core–shell particles. ► A peak capacity of 760 was obtained in 2h on a 450mm coupled column system. ► Operating a 900mm coupled system at 1200bar yielded a peak capacity of 1360.

Fast analysis of synthetic antioxidants in edible vegetable oil using trilinear component modeling of liquid chromatography–diode array detection data

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Jian-Yao Wang, Hai-Long Wu, Yao Chen, Yan-Mei Sun, Yong-Jie Yu, Xiao-Hua Zhang, Ru-Qin Yu
A new chromatographic methodology is presented for fast quantitative analysis of ten synthetic phenolic antioxidants in five kinds of oil samples: propyl gallate (PG), 2,4,5-trihydroxybutyrophenone (THBP), tert-butylhydroquinone (TBHQ), nordihydroguaiaretic acid (NDGA), ethoxyquin (EQ), 3-tert-butyl-4- hydroxyanisole (BHA), octyl gallate (OG), 2,6-di-tert-butyl-4-hydroxymethyphenol (Ionox-100), dodecyl gallate (DG), 3,5-di-tert-butyl-4-hydroxytoluene (BHT). The second-order calibration, with second-order advantage, based on the alternating penalty trilinear decomposition (APTLD) algorithm has shown to be an excellent tool for modeling the three-way data, where overlapping peaks, uncalibrated inteferences, and baseline drift existed, making the fast determination and resolution of the phenolic antioxidants in oils possible. Such extraction procedure in which the antioxidants of interest would be seperated is unnecessary and the ten antioxidants can be eluted within 6mins. For the validation of the method, linearity, root-mean-square error of prediction (RMSEP) and limit of detection (LOD) have been performed. The average recovery of antioxidants ranges from 94.9 to 106.1% and the ten analytes can be adequately determined with limits of detection of 0.18–5.72μgml⁻¹.

Highlights

► Ten Synthetic phenolic antioxidants (SPAs) can be eluted within 6min. ► The extraction of the SPAs in oils is unnecessary. ► Baseline drift and peak overlapping were successfully resolved by our method.

Impact of carrier fluid composition on recovery of nanoparticles and proteins in flow field flow fractionation

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Samantha Schachermeyer, Jonathan Ashby, MinJung Kwon, Wenwan Zhong
Flow field flow fractionation (F4) is an invaluable separation tool for large analytes, including nanoparticles and biomolecule complexes. However, sample loss due to analyte-channel membrane interaction limits extensive usage of F4 at present, which could be strongly affected by the carrier fluid composition. This work studied the impacts of carrier fluid (CF) composition on nanoparticle (NP) recovery in F4, with focus on high ionic strength conditions. Successful analysis of NPs in a biomolecules-friendly environment could expand the applicability of F4 to the developing field of nanobiotechnology. Recovery of the unfunctionalized polystyrene NPs of 199, 102, and 45nm in CFs with various pH (6.2, 7.4 and 8.2), increasing ionic strength (0–0.1M), and different types of co- and counter-ions, were investigated. Additionally, elution of the 85nm carboxylate NPs and two proteins, human serum albumin (HSA) and immunoglobulin (IgG), at high ionic strengths (0–0.15M) was investigated. Our results suggested that (1) electrostatic repulsion between the negatively charged NPs and the regenerated cellulose membrane was the main force to avoid particle adsorption on the membrane; (2) larger particles experienced higher attractive force and thus were influenced more by variation in CF composition; and (3) buffers containing weak anions or NPs with weak anion as the surface functional groups provided higher tolerance to the increase in ionic strength, owing to more anions being trapped inside the NP porous structure. Protein adsorption onto the membrane was also briefly investigated in salted CFs, using HSA and IgG. We believe our findings could help to identify the basic carrier fluid composition for higher sample recovery in F4 analysis of nanoparticles in a protein-friendly environment, which will be useful for applying F4 in bioassays and in nanotoxicology studies.

Highlights

► High repulsive force between NPs and membrane can minimize particle adsorption. ► Weaker anion in solution or on NP surface causes lower NP adsorption at high conc. ► Highly charged counter ions increases NP adsorption on membrane significantly. ► Protein conformation plays an important role in protein–membrane interaction.

Development of heart-cutting multidimensional gas chromatography coupled to time of flight mass spectrometry for silicon speciation at trace levels in gasoline samples

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Fabien Chainet, Charles-Philippe Lienemann, Jérémie Ponthus, Marion Courtiade, Olivier François Xavier Donard
To improve the understanding of hydrotreatment (HDT) catalyst poisoning by silicon species, these molecules must be characterized in petroleum products using powerful analytical systems. Heart-cutting gas chromatography coupled to time of flight mass spectrometry (GC–GC/TOFMS) method equipped with a Deans switch (DS) system was developed for the direct characterization of target silicon compounds at trace level (μgkg⁻¹) in gasoline samples. This method was performed to identify silicon compounds never characterized before. After the selection of the second dimension column using GC–GC–FID, GC–GC/TOFMS was performed. The calibration curves obtained by the GC–GC/TOFMS method were linear up to 1000μgkg⁻¹. Limits of detection (LOD) were ranging from 5 to 33μgkg⁻¹ in spiked gasoline. The method provided sufficient selectivity and sensitivity to characterize known silicon compounds thanks to their specific ions and their retention times. The analysis of a naphtha sample by GC–GC/TOFMS has shown the presence of cyclic siloxanes (D n ) as major compounds of PDMS thermal degradation with the occurrence of linear siloxanes, especially hexamethyldisiloxane (L2), which was never characterized in petroleum products but already known as severe poison for catalyst.

Highlights

► A GC–GC/TOFMS was developed for the characterization of silicon compounds. ► Silicon species, potentially poisons, were identified at trace levels. ► A real advance for silicon speciation to understand catalyst poisoning.

Fully automated determination of macrocyclic musk fragrances in wastewater by microextraction by packed sorbents and large volume injection gas chromatography–mass spectrometry

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Laura Vallecillos, Eva Pocurull, Francesc Borrull
A fully automated method has been developed for the determination of eight macrocyclic musk fragrances in urban wastewater. The procedure includes the enrichment of the analytes by microextraction by packed sorbent (MEPS) followed by large volume injection–gas chromatography–mass spectrometry (LVI–GC–MS). The main factors in the MEPS technique were optimized. For all of the analytes, the highest enrichment factors were achieved when 4mL samples were extracted by using C18 MEPS-sorbent and 50μL of ethyl acetate were used for desorption. The eluate was directly analysed by GC–MS. Detection limits were found to be between 5ngL⁻¹ and 10ngL⁻¹, depending on the target analytes. In addition, under optimized conditions, the method gave good levels of intra-day and inter-day repeatability in wastewater samples with relative standard deviation (RSD) (n =3, 1000ngL⁻¹) less than 5% and 9%, respectively. The applicability of the method was tested with wastewater samples from two influent and effluent urban wastewater treatment plants (WWTPs). The analysis of influent urban wastewater revealed the presence of most of the macrocylic musks at concentrations higher than the method quantification limits (MQLs), being the most abundant analyte ambrettolide at 9.29μgL⁻¹. In addition, the analyses of effluent urban wastewater showed a decrease in the concentrations with macrocyclic musk concentrations of between not detected (n.d.) and 2.26μgL⁻¹ being detected.

Highlights

► The work was focused on the determination of 8 macrocyclic musk in urban wastewater. ► MEPS instead of SPE have been used to preconcentrate the target analytes. ► Large volume injection permitted the automation of the whole analytical method. ► Method detection and quantification limits were found in the low ngL⁻¹. ► Good values of intra-day and inter-day repeatabilities have been obtained.

Linear solvation energy relationships as classifiers in non-target analysis – A gas chromatographic approach

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Nadin Ulrich, Jana Mühlenberg, Heiko Retzbach, Gerrit Schüürmann, Werner Brack
Linear solvation energy relationships (LSERs) are applied as classifiers to predict the logarithmic retention factors log k from the structures of candidate compounds in non-target analysis. By comparison of the predicted value with the experimentally determined log k, progressive exclusion of candidates is done. The approach is based on the determination of stationary phase parameters to describe ten different gas chromatographic columns under four isothermal conditions. To demonstrate retention prediction and the application of the classifier model, twelve compounds with the molecular formula C12H10O2 were selected, while experimental log k values were compared to the predicted values and exclusion of potential candidate compounds was performed. The analytical power of the approach was demonstrated on the basis of experimentally determined compound descriptors achieved from gas chromatographic measurements. The prediction got less accurate when calculated compound descriptors were employed. For the time being insufficient precision in estimating the descriptors limits the possibility to exclude candidate compounds in non-target analysis. It is expected that new approaches to estimate compound descriptors, will improve this situation. At present, the insufficient accuracy of descriptor estimates can be dealt with larger prognosis intervals. Furthermore, the combination of two stationary phases with corresponding retention prediction further advanced the exclusion of potential candidates. The most appropriate pair of stationary phases was selected by the application of four different orthogonal strategies. In addition, the classifier was applied for a validation set with different molecular composition, where column selection was considered on the basis of the differences in the compound descriptors of the corresponding candidate compounds.

Highlights

► Retention prediction by LSER models on 10 GC columns and 4 temperatures. ► Comparison of prediction performance with calculated and experimental descriptors. ► Demonstration of application as classifier in non-target analysis with set of isomers. ► Validation for candidate compounds with different molecular composition. ► Column selection for compound classes to optimize candidate exclusions.

A novel derivatization approach for determination of ketamine in urine and plasma by gas chromatography–mass spectrometry

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Kaoqi Lian, Pingping Zhang, Lingmei Niu, Siyuan Bi, Shipeng Liu, Lingling Jiang, Weijun Kang
A new method was developed for determination of ketamine (KT) in urine and plasma samples by derivatization and gas chromatography–mass spectrometry. In this article, KT was first derivatized with sodium nitrite to volatile N-nitrosamines under acidic condition. Then the derivative had been identified by the mass spectra. The derivatization conditions including the amount of hydrochloric acid, the amount of sodium nitrite, reaction temperature, reaction time and the extraction reagents were optimized. Calibration curves were linear in the range of 0.04–20μgmL⁻¹ for KT, and the limit of detection (LOD) and limit of quantitation (LOQ) were 0.01μgmL⁻¹ and 0.04μgmL⁻¹, respectively. The results of recovery indicated that the method had good precision and reproducibility. Compared with existing derivatization methods, this method provided a rapid, convenient, effective and low-cost way for gas chromatography method of KT quantification.

Highlights

► A new derivatization method for determination of KT by GC–MS has been developed. ► Comparison with other methods, the method is simple, rapid, effective, and low-cost. ► The recovery and precision of the method are highly satisfactory. ► The method will provide a new strategy for the detection of secondary amine drugs.

A sensitive and selective method for the determination of selected pesticides in fruit by gas chromatography/mass spectrometry with negative chemical ionization

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
N. Belmonte Valles, M. Retamal, M. Mezcua, A.R. Fernández-Alba
Multiresidue methods (MRMs) for pesticides residues determination in fruit and vegetables, based on GC–MS, are mainly performed in electron impact ionization mode. However an important group of them provide much better response working in negative chemical ionization mode due to the elimination of a high percentage of background signal. Considering that a selective and sensitive method has been developed for the determination of multiclass pesticide residues in different commodities by GC–MS with a triple stage quadrupole analyzer (GC–TSQ–MS); the pesticide signal has been optimized in MS–MS whilst working in negative chemical ionization mode using methane as the reagent gas. The proposed method was fully validated for 53 compounds in tomato, apple and orange matrices. The obtained limits of determination were lower than 0.1μg/kg for more than 50% of the pesticides studied, and lower than 1μg/kg for all pesticides studied, except for cypermethrin, boscalid, bifenthrin and deltamethrin. Linearity was studied in the 0.5–50μg/kg range and a linear response was obtained for all pesticides in all matrices. Recoveries were evaluated at two different levels (1 and 50μg/kg) and recoveries were ranged between 70 and 120% in tomato, apple and orange, except in the cases of chlorfenapyr, ofurace, chlozolinate, chlorothalonil, tolylfluanid and dichlofluanid with recovery values close to 60% at 1μg/kg fortification levels. Repetitivity was evaluated and the relative standard deviation (RSD%) was lower than 10% in all cases. The developed method was employed in the analysis of real samples intended for baby food and the obtained results showed that 50% of the samples were positive for different pesticide residues. The concentration range detected was between 5 and 100μg/kg. The positive detection of OCs was particularly noticeable; these included chlorothalonil, fenhexamide, clorpyrifos and lambda cyhalothrin, which are very persistent and toxic with low acute reference dose. Endosulfan sulfate, which is not approved, was detected at a low concentration.

Highlights

► Selective and sensitive method for determination of multi-class pesticides. ► GC–MS with a triple stage quadrupole analyzer (GC–TSQ–MS). ► Working in negative chemical ionization mode using methane as reactive gas. ► Analysis of real samples intended for baby food. ► Extraction method: liquid extraction using ethyl acetate as extraction solvent.

Imprinted polymers for chiral resolution of (±)-ephedrine, 4: Packed column supercritical fluid chromatography using molecularly imprinted chiral stationary phases

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Richard J. Ansell, Janice K.L. Kuah, Dongyao Wang, Clare E. Jackson, Keith D. Bartle, Anthony A. Clifford
(−)-Ephedrine-molecularly imprinted polymers (MIPs) have been successfully used as stationary phases in supercritical fluid chromatography for the separation of (±)-ephedrine enantiomers. This approach combines the simple preparation and predictable elution order of MIP stationary phases with the superior mobile phase diffusivity and low viscosity of supercritical fluid mobile phases. The optimised mobile phase comprised supercritical carbon dioxide with a modifier consisting of MeOH/isopropylamine/H2O 93:5:2 (v/v/v). In many cases, better resolution separations were observed compared to when liquid mobile phases were used, and better separations achieved at high sample loads, although interestingly the MIPs which work best in SFC are different from the MIPs that work best in HPLC with an amine modifier. The MIP stationary phases were stable under the conditions employed and the chromatography was reproducible. This work opens the door to exploiting MIP stationary phases in preparative SFC.

Highlights

► MIPs successfully used as stationary phases in separation of (±)-ephedrine by SFC. ► MIPs are stable under the conditions used and the chromatography is reproducible. ► Better separations achieved with the best MIP in SFC than with any of them in HPLC. ► The mobile phase is carbon dioxide with a modifier of methanol/isopropylamine/water.

Processes involved in sweeping under inhomogeneous electric field conditions as sample enrichment procedure in micellar electrokinetic chromatography

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Mohamed El-Awady, Carolin Huhn, Ute Pyell
Sweeping under inhomogeneous electric field conditions has been described as a process that includes stacking or destacking of the micelles when entering the sample zone, sweeping of analytes by the stacked or destacked micelles, and destacking or stacking of the swept analyte zone. However, there is ongoing debate that not only the retention factor of the analyte but also the electric conductivity of the sample solution or the concentration of an added salt can have an impact on the enrichment efficiency. Revisiting the equations describing sweeping, a factor θ (phase ratio shift factor) is defined to quantitatively describe the change of the retention factor between the sample and separation zones. The influence of the sample matrix composition on the experimentally obtained sweeping efficiency is studied with SDS as pseudostationary phase taking parabens, benzamide and anilines as model analytes. To this end, a robust and reliable method for the assessment of the sweeping efficiency is developed. The values obtained via this method are very precise and agree well with theoretically predicted ones. The results obtained for varied buffer concentration and varied concentration of NaCl in the sample solution show that under the conditions of our experimental study, the approximation of assuming θ to be equal to the reciprocal value of the field strength enhancement factor γ is valid. Accordingly, the sweeping efficiency for neutral analytes is independent of the electric conductivity of the sample matrix. It is also shown that under specific conditions unexpectedly high enrichment factors are obtained which are ascribed to the focusing of neutral analytes by micellar transient isotachophoresis (mtITP). The results obtained in this study can be used as a guide for better understanding of the sweeping process and the factors affecting the sweeping efficiency in micellar electrokinetic chromatography (MEKC).

Highlights

► A new reliable method for the determination of sweeping efficiency is developed. ► Sweeping under inhomogeneous electric field condition is a complex multistep process. ► Sweeping efficiency is independent of the electric conductivity of the sample matrix. ► Focusing by micellar transient isotachophoresis is suggested under specific cases. ► Better understanding of the sweeping process and related phenomena is achieved.

Molecularly imprinted nanoparticles with nontailing peaks in capillary electrochromatography

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
Xiao Liu, Ze-Hui Wei, Yan-Ping Huang, Jin-Rong Yang, Zhao-Sheng Liu
The combination of microparticles of molecularly imprinted polymers (MIPs) with partial filling capillary electrochromatography (CEC) has previously been demonstrated for the enantiomer separation. In this paper, precipitation polymerization was used to prepare d-zopiclone imprinted nanoparticles (50–80nm) by a strategy of the dilution of pre-polymerization mixtures. The influence of some important parameters on the preparation of MIPs nanoparticles, including template to monomer ratio, type and amount of cross-linking monomer, and functional monomer composition ratio were investigated. In addition, the effect of separation condition, e.g., organic modifier content, pH value and salt concentration of buffer, on the electrochromatographic behavior of the MIP nanoparticles were studied. In spite of lower selectivity factor (1.11), high column performance (theoretical plates 41,400) of template was obtained and the resolution of enantiomers separation was 4.75 under the optimized conditions. Compared to the previously reported MIP microparticles, the MIP nanoparticles showed good peak symmetry and an ability of high speed separation (<15min) in CEC mode.

Highlights

► Molecularly imprinted nanoparticles with size of 50–80nm were prepared with zopiclone as template. ► Baseline separation of enantiomer separation can be achieved with imprinted nanoparticles in CEC mode. ► Polymerization factors on the imprinting effect of MIP nanoparticles were investigated. ► Imprinted nanoparticles showed higher efficiency for template with good peak symmetry.

The role of harmonized, gas and liquid chromatography mass spectrometry in the discovery of the neolignan balanophonin in the fruit wall of Cirsium vulgare

22 October 2012, 08:56:27

Publication year: 2012
Source:Journal of Chromatography A, Volume 1264
I. Boldizsár, M. Kraszni, F. Tóth, G. Tóth, A. Sólyomváry, B. Noszál, Gy. Záray, I. Molnár-Perl
In order to identify and quantify fruit-lignans of Cirsium vulgare – authors introduced a special analysis system: with particular attention to the lignans enrichment/separation course. These synchronized, germination and enzymatic hydrolysis processes were followed by complementary gas and liquid chromatography, coupled with special mass selective detections (GC–MS, LC–MS/MS, LC–TOF/MS) and confirmed by nuclear magnetic resonance (NMR) spectroscopy. Mass fragmentations and NMR evidences, proved that the two main medicinal lignan constituents of the fruits of Cirsium vulgare are the neolignan-type, free balanophonin and the butyrolactone-type tracheloside. As novelty to the field, these two lignans of different chemical structures could be quantitatively extracted, separately from each others, without impurities. Balanophonin and tracheloside do accumulate in the fruits of C. vulgare, separately: balanophonin was found, in enormous high concentrations, in the fruit wall (23.2–24.9mg/g), while in embryo part tracheloside was determined (20.3mg/g), exclusively. Consequently, the optimum source of balanophonin proved to be the fruit wall, while tracheloside, – providing trachelogenin upon enzymatic hydrolysis, – could be obtained from the embryo parts of fruits. As further novelties of the study balanophonin was identified and quantified at the first time with on-line chromatographic technique, in free form, without authentic standard compound.

Highlights

► Balanophonin and tracheloside lignans were found at first in Cirsium vulgare's fruit. ► Harmonized principle was introduced to the lignans’ enrichment/separation course. ► Complementary GC–MS, LC–MS/MS, LC–TOF/MS methods and NMR techniques were applied. ► Germination and enzymatic hydrolysis steps resulted in the impurity free lignans. ► Accumulation of balanophonin (fruit wall) and tracheloside (embryo) was quantified.

Shallow Plates Increase Stacking or Storage Capacity

Porvair Sciences has developed a range of shallow 96-well plates for storage / collection applications in the fields of cell biology, molecular biology, drug discovery, screening and genomics.

The new shallow plates are available with well capacities of 350ul, 270ul and 220ul in a height of just 14.7 mm.  This allows more plates to be stored or stacked in a give space. Offered with flat, round or v-bottom - a choice of shallow plate is available optimised for particulate collection or liquid removal.  Raised rims on the 96-well shallow plates improve sealing and stop cross contamination.

Porvair 96-well shallow plates are manufactured in a clean room environment from extractable-free polypropylene to ensure the integrity of your stored samples.  Combining an affordable price with uncompromising high quality, the 96-well shallow plates are precisely manufactured to comply with ANSI/SBS dimensions** ensuring complete compatibility with all automated sample handling systems, microplate readers and washers.

For further information or a free sample plate please contact Porvair Sciences on telephone +44-1372-824290 or email int.sales@porvair-sciences.com.

New WelchNet Titan Oil-Free Vacuum Systems

Welch-Ilmvac has introduced the WelchNet Titan, a microprocessor controlled system of high capacity PTFE diaphragm vacuum pumps for Multi-User Laboratory Installations.

The pumps work individually or in tandem as the laboratory vacuum demand requires, holding vacuum level even if an individual pump needs maintenance.

Features include:

• Intelligent Vacuum Control
• Chemical Resistant
• Green technology
• Oil Free
• Energy Efficient
• Low Maintenance

The Titan is mounted on a mobile base frame which is easily positioned for adaptation to existing plumbing. Titan-4 and Titan-6 are systems utilizing 4 or 6 PTFE diaphragm pumps to provide efficient vacuum on demand for up to 30 separate users.

The individual pumps start up in tandem and are successively switched off as working vacuum pressure is attained. One or more pumps come on in response to vacuum demand, rotating usage to distribute pump wear and extend maintenance interval.

With manufacturing on three continents, global distribution, and an extensive service network, Welch-Ilmvac provides expert technical solutions and value-driven vacuum products for the global marketplace.

To learn more about Welch-Ilmvac, please visit www.welchvacuum.com

New Malaria Monoclonal Antibodies

Malaria is a mosquito-borne parasitic infection caused by several species of Plasmodium. It is prevalent world wide in subtropical regions of Africa, Asia and the Americas. Symptoms include fever and headache but can proceed to coma and death.

The majority of deaths are caused by P. falciparum. During the blood stage infection, P. falciparum secretes large quantities of a glycoprotein termed Histidine- Rich Protein II (HRP II). Detection of HRP II in serum or plasma correlates to active parasitemia.

ViroStat has released a new set of monoclonal antibodies to the HRP II protein of P. falciparum. These antibodies should be useful to researchers and those needing to develop rapid tests for this protein.

To download the data sheet for these NEW Antibodies and to obtain pricing, go to the ViroStat website at www.virostat-inc.com or call 207-856-6620

ViroStat, Inc. is a primary manufacturer of infectious disease antigens and antibodies, supplying researchers and manufacturers since 1985. Specialties include high affinity antibodies to Flu A, Flu B, RSV & Strep A for use in rapid lateral flow devices as well as antibodies to food-borne pathogens and toxins. Also, many specificities to HCV, HBV, CMV & EBV for use in anti-viral HTS assays.

ViroStat, Inc.
PO Box 8522
Portland, ME 04104 USA

Phone: 207-856-6620
Fax: 207-856-6864
E-mail: info@virostat-inc.com
Web: www.virostat-inc.com

AirClean Systems launches new Patriot ductless fume hoods.

AirClean Systems, the North American leader in ductless containment since 1992, announces the introduction of its newest product line: Patriot Ductless Fume Hoods. Patriot ductless hoods incorporate much of the advanced technology of AirClean’s Independence fume hood with the cost effective backbone of AirClean’s AC4000 folding and sliding-sash ductless fume hoods.

Patriot ductless fume hoods feature the easy-to-use AirSafe™ TOUCH automatic safety controller for added operator safety. This color touchscreen controller automatically increases or decreases blower speed to maintain the user’s pre-set face velocity, ensuring airflow is within standard operating parameters. The current face velocity is displayed at all times. AirSafe TOUCH also monitors the bonded carbon filtration bed, alerting the user audibly and visually should filter saturation occur. Patriot features a unique ‘application confirmation’ sequence that is required with every use of the hood. AirSafe TOUCH displays the approved chemical class for the hood, and waits for a confirmation from the user before allowing the hood to be used.

In addition to safety features, AirSafe TOUCH also provides a multi-language and multi-unit capability not found in most ductless hoods. With the press of a button, users can switch the controller language between English, Spanish, French and German. Airflow can be displayed in both linear feet per minute (LFM) and meters per second (m/s).

Patriot ductless hoods eliminate the need for costly installation, ductwork and over-built HVAC systems associated with traditional fume hood use within the laboratory. An on-board energy meter, accessed via AirSafe TOUCH, displays the real-time and life-time energy use of the hood.

AirClean Systems’ unique bonded carbon filtration is standard on all Patriot ductless fume hoods. For added application breadth and capacity, Silconazyne™ filtration is also available for Patriot.

Patriot’s rolled-entry design combined with AirZone™ baffling provides laminar flow within the cabinet, preventing eddy currents and keeping fumes or particulate from escaping the hood. Seamless, thermally welded polypropylene construction means the Patriot will never rust, providing years of service life. All electronics and blowers are post-filter, so they are never exposed to chemicals used in the hood.

All AirClean Systems ductless fume hoods are made in the USA and ship fully assembled, requiring very minimal installation. Simply place on a cabinet, stand or benchtop and plug into a standard 110V or 220V outlet. The Patriot ductless fume hood can be installed and used within minutes of being removed from its shipping container.

Patriot ductless fume hoods will be available beginning in August. Folding sash models are initially available in 36” and 48” widths, and sliding sash models are initially available in 48” and 72” widths.

Just Published: Journal of Pharmaceutical and Biomedical Analysis

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 Pharmaceutical and Biomedical Analysis
http://rss.sciencedirect.com/publication/science/5266

Selected papers from the latest issue:

Phospholipids covalently attached to silica particles as stationary phase in nano-liquid chromatography

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Clara-Eugenia Baños, Susanne K. Wiedmer, Jan-Henrik Smått, Motolani Sakeye, Jana Lokajová, Marja-Liisa Riekkola
Silica particles were covalently modified with phospholipids and used as packing material for nano-liquid chromatography (nano-LC). This modification involved aminopropylsilylation of the raw silica particles using 3-(aminopropyl)-triethoxysilane, covalent binding of glutaraldehyde molecules to the aminopropylsilylated particles, and finally covalent binding of different phospholipid vesicles containing primary amino groups to the iminoaldehyde silica particles. Capillaries with an inner diameter of 100μm were packed with phospholipid-coated silica particles using a slurry packing method. The packed capillaries were tested in nano-LC with UV-detection for the separation of acidic, neutral, and basic model analytes. The effect of the buffer ion on the retention factor of the analytes was evaluated using buffer solutions with constant ionic strength and pH. In addition, the effect of the volume of methanol in the mobile phase was studied. The calculated distribution coefficients (log K D) of the model compounds were in agreement with those reported in the literature. A good correlation between log K D values and octanol/water partitioning coefficients (P o/w) for neutral hydrophobic analytes was obtained proving the applicability of the method for predicting partitioning of the compounds with the biomembranes.

Evaluation of metal concentrations in mentha herbal teas (Mentha piperita, Mentha pulegium and Mentha species) by inductively coupled plasma spectrometry

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
C. Rubio, J.R.D. Lucas, A.J. Gutiérrez, D. Glez-Weller, B. Pérez Marrero, J.M. Caballero, C. Revert, A. Hardisson
Phytopharmaceuticals are gaining popularity worldwide; however, cases of adverse effects and drug interactions have also increased. One reason is in the high metal content both as ingredients but also as contaminants. Metal monitoring in food, like herbal teas, provides basic information on safety aspects in regulatory processes as well as nutritional values. In the present work, Cd, Pb, K, Na, Ca, Mg, Al, B, Ba, Co, Cr, Cu, Fe, Mn, Zn, Li, Ni, and Mo were determined by inductively coupled plasma spectrometry (ICPS) in 36 samples of Mentha sp. Mint tea bags and loose leaves were randomly obtained from supermarkets, traditional markets, herbal stores, and pharmacies in Tenerife (Canary Islands, Spain). Metal contents varied significantly, dependent on the stores the products were purchased in and on tea packaging (loose leaves versus tea bags). Pb analyses revealed levels (0.65±0.71mg/kg) below legal limits. The maximum permissible limit for Cd, 0.3mg/kg, set by the WHO for medicinal plants, was exceeded by 19.44% of the samples (0.22±0.13mg/kg), but all values were below the limit given in the European Pharmacopoeia for this metal (4mg/kg). We observed high Al (151.24±162.73mg/kg) and Li (5.46±3.94mg/kg) levels. B, Ba, Co, Cr, Cu, Fe, Mn, Ni, Zn, and Mo mean levels were 20.51, 14.15, 0.26, 1.65, 10.65, 406.00, 55.05, 1.72, 33.67, and 0.73mg/kg, respectively. Mean Ca, Mg, K, and Na were detected in concentrations of 10.32, 3.83, 7.23 and 1.17g/kg, respectively. In conclusion, metal exposure through herbal mint teas does not seem to be of health concern, as to most of the studied metals, but regulatory limits for Al contents should be imposed.

Qualitative screening for adulterants in weight-loss supplements by ion mobility spectrometry

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Jamie D. Dunn, Connie M. Gryniewicz-Ruzicka, Daniel J. Mans, Laura C. Mecker-Pogue, John F. Kauffman, Benjamin J. Westenberger, Lucinda F. Buhse
Ion mobility spectrometry (IMS) served as a rapid, qualitative screening tool for the analysis of adulterated weight-loss products. We have previously shown that sibutramine extracted into methanol from dietary supplements can be detected at low levels (2ng) using a portable IMS spectrometer, and have adapted a similar method for the analysis of additional weight-loss product adulterants. An FDA collaborative study helped to define the limits for fluoxetine with a limit of detection of 2ng. We also evaluated more readily available, less toxic extraction solvents and found isopropanol and water were comparable to methanol. Isopropanol was favored over water for two reasons: (1) water increases the analysis time and (2) aqueous solutions were more susceptible to pH change, which affected the detection of sibutramine. In addition to sibutamine and fluoxetine, we surveyed 11 weight-loss adulterants; bumetanide, fenfluramine, furosemide, orlistat, phenolphthalein, phentermine, phenytoin, rimonabant, sertraline and two sibutramine analogs, desmethylsibutramine and didesmethylsibutramine, using portable and benchtop ion mobility spectrometers. Out of these 13 active pharmaceutical ingredients (APIs), portable and benchtop ion mobility spectrometers were capable of screening products for 10 of these APIs. The developed procedure was applied to two weight-loss dietary supplements using both portable and benchtop instruments. One product contained didesmethylsibutramine while the other contained didesmethylsibutramine and phenolphthalein.

Drug release into hydrogel-based subcutaneous surrogates studied by UV imaging

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Fengbin Ye, Susan Weng Larsen, Anan Yaghmur, Henrik Jensen, Claus Larsen, Jesper Østergaard
Upon subcutaneous administration, the distribution of drug between the delivery vehicle and the biological tissue critically affects the absorption of drug substances. Utilization of physical models resembling the native tissues appears promising for obtaining a detailed understanding of the performance of drug delivery systems based on in vitro experiments. The objective of this study was to evaluate a UV imaging-based method for real-time characterization of the release and transport of piroxicam in hydrogel-based subcutaneous tissue mimics/surrogates. Piroxicam partitioning from medium chain triglyceride (MCT) into 0.5% (w/v) agarose or 25% (w/v) F127-based hydrogels was investigated by monitoring the concentration profiles of the drug in the gels. The effect of pH on piroxicam distribution and diffusion coefficients was studied. For both hydrogel systems, the diffusion of piroxicam in the gels was not affected significantly by the pH change from 4.0 to 7.4 but a considerable change in the oil–gel distribution coefficients was found (24 and 34 times less at pH 7.4 as compared those observed at pH 4.0 for F127 and agarose gels, respectively). In addition, the release and transport processes of piroxicam upon the injection of aqueous or MCT solutions into an agarose-based hydrogel were investigated by UV imaging. The spatial distribution of piroxicam around the injection site in the gel matrix was monitored in real-time. The disappearance profiles of piroxicam from the injected aqueous solution were obtained. This study shows that the UV imaging methodology has considerable potential for characterizing transport properties in hydrogels, including monitoring the real-time spatial concentration distribution in vitro after administration by injection.

Comparative analysis of zaleplon complexation with cyclodextrins and hydrophilic polymers in solution and in solid state

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Jasna Jablan, Gábor Szalontai, Mario Jug
The aim of this work was to investigate the potential synergistic effect of water-soluble polymers (hypromellose, HPMC and polyvinylpyrrolidone, PVP) on zaleplon (ZAL) complexation with parent β-cyclodextrin (βCD) and its randomly methylated derivative (RAMEB) in solution and in solid state. The addition of HPMC to the complexation medium improved ZAL complexation and solubilization with RAMEB (K ZAL/RAMEB =156±5M⁻¹ and K ZAL/RAMEB/HPMC =189±8M⁻¹; p <0.01), while such effect was not observed for βCD (K ZAL/βCD =112±2M⁻¹ and K ZAL/βCD/HPMC =119±8M⁻¹; p >0.05). Although PVP increased the ZAL aqueous solubility from 0.22 to 0.27mg/mL, it did not show any synergistic effects on ZAL solubilization with the cyclodextrins tested. Binary and ternary systems of ZAL with βCD, RAMEB and HPMC were prepared by spray-drying. Differential scanning calorimetry, X-ray powder diffraction and scanning electron microscopy demonstrated a partial ZAL amorphization in spray-dried binary and ternary systems with βCD, while the drug was completely amorphous in all samples with RAMEB. Furthermore, inclusion complex formation in all systems prepared was confirmed by solid-state NMR spectroscopy. The in vitro dissolution rate followed the rank order ZAL/RAMEB/HPMC>ZAL/RAMEB=ZAL/βCD/HPMC>ZAL/βCD≫ZAL, clearly demonstrating the superior performance of RAMEB on ZAL complexation in the solid state and its synergistic effect with HPMC on drug solubility. Surprisingly, when loaded into tablets made with insoluble microcrystalline cellulose, RAMEB complexes had no positive effect on drug dissolution, because HPMC and RAMEB acted as a binders inside the tablets, prolonging their disintegration. Oppositely, the formulation with mannitol, a soluble excipient, containing a ternary RAMEB system, released the complete drug-dose in only 5min, clearly demonstrating its suitability for the development of immediate-release oral formulation of ZAL.

Highlights

► Zaleplon (ZAL) complexation with RAMEB and HPMC enhanced its solubility about 9 times. ► βCD was less effective in ZAL solubilization, not forming ternary complexes with HPMC or PVP. ► CP-MAS confirmed the inclusion complexation for all spray dried binary and ternary samples. ► βCD complexes contained 39.8–31.1% of crystalline ZAL; RAMEB complexes were amorphous. ► ZAL/RAMEB/HPMC complex tabletted with mannitol gained immediate-release formulation.

Analysis of synthetic cannabinoids in herbal blends by means of nano-liquid chromatography

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Gustavo Merola, Zeineb Aturki, Giovanni D’Orazio, Rossella Gottardo, Teodora Macchia, Franco Tagliaro, Salvatore Fanali
In this study, a rapid and simultaneous separation of 12 synthetic cannabinoids and Δ⁹-tetrahydrocannabinol (Δ⁹-THC) in herbal blends was obtained by means of nano-liquid chromatography (nano-LC). The nano-LC experiments were performed in a 100μm i.d. capillary column packed with Cogent^® bidentate C18 silica particles for 25.0cm. All compounds were resolved using an isocratic elution mode in less than 30min. A mobile phase containing ACN/MeOH/H2O/formic acid 69/5/25/1 (v/v/v/v) was employed for the chromatographic separation. The developed analytical method was validated in terms of precision, linearity, sensitivity and accuracy. Under optimal nano-LC–UV conditions, the resulting RSD percentages for intra-day and inter-day repeatability, related to retention time and peak area, were below 2.98 and 6.40%, respectively. Limits of detection and quantification were 0.2 and 0.5μg/mL, respectively, for all the studied compounds. Linearity was assessed in the concentration range of interest for all analytes with determination coefficients r ² ≥0.9975. The method was then applied to the determination of synthetic cannabinoids in herbal blends. Quantitative analyses of the cannabimimetic compounds in six products showed that there was a wide difference in the concentration of the studied compounds among different products. Further, the nano-LC system was coupled with a mass spectrometer measuring the MS and MS–MS spectra to unequivocally identify the cannabinoids present in smoking mixtures.

Highlights

► Twelve synthetic cannabinoids and tetrahydrocannabinol were separated by nano-LC. ► Capillary columns packed with a C18 stationary phase were used for the separations. ► Analytes of forensic interest were separated by isocratic elution mode. ► Nano-LC was coupled with mass spectrometry for compounds characterization.

Characterization of physalins and fingerprint analysis for the quality evaluation of Physalis alkekengi L. var. franchetii by ultra-performance liquid chromatography combined with diode array detection and electrospray ionization tandem mass spectrometry

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Yunliang Zheng, Lianjun Luan, Yong Chen, Yiping Ren, Yongjiang Wu
Physalins are important bioactive compounds from genus Physalis. They often occur as isomers, which makes the structural elucidation difficult. In the present study, the fragmentation behavior and UV characteristics of seven physalins from genus Physalis were firstly investigated using electrospray ionization tandem mass spectrometry (ESI-MS/MS) and diode array detection (DAD). Combined with ultra-performance liquid chromatography (UPLC) and DAD, the established approach to the structural identification of physalins by ESI-MS/MS was then applied to the analysis of Physalis alkekengi L. According to the UPLC retention behavior, the diagnostic UV spectra and the molecular structural information provided by MS/MS spectra, about 19 fingerprint peaks were identified, including 14 physalins and 5 other compounds. Finally, the established fingerprint method was applied to the analysis of 31 P. alkekengi L. samples collected from different locations, which reflected their similar chemical constituent properties. The proposed method provides a scientific and technical platform to the herbal industry for quality control and safety assurance of herbal preparations that contain this class of physalins.

Analysis of total and unbound hydromorphone in human plasma by ultrafiltration and LC–MS/MS: Application to clinical trial in patients undergoing open heart surgery

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Teijo I. Saari, Jörg Fechner, Harald Ihmsen, Jürgen Schüttler, Christian Jeleazcov
A method for a sensitive and specific analysis of hydromorphone total and unbound drug concentrations in human plasma was developed and validated. Sample preparation was preceded with an ultrafiltration step to separate the unbound drug from the protein bound fraction of hydromorphone. Both the ultrafiltrate and plasma samples were extracted with solid-phase extraction and substituted with stable isotope-labeled hydromorphone that was used as internal standard. Chromatographic separation was performed by gradient elution with UPLC-like system and eluates were analyzed by tandem mass spectrometry equipped with an electrospray ionization source. Sample preparation was optimized for good recovery of hydromorphone and the results were consistent. Calibration curves demonstrated linearity in the concentration range of 78–5000pg/ml for analysis of both total and unbound concentrations of hydromorphone. The limit of detection was 1pg and the lower limit of quantification was 78pg/ml for both total and unbound hydromorphone plasma drug concentrations. Intra- and interassay reproducibility and inaccuracy did not exceed 10%. Hydromorphone was on the average 14% bound to plasma proteins, supporting the previously published unreferenced statements that the protein binding of hydromorphone is low. Method was applied to a clinical trial in patients undergoing open heart surgery to generate a target controlled infusion model for the postoperative patient controlled analgesia with hydromorphone.

Determination of emodin in L-02 cells and cell culture media with liquid chromatography–mass spectrometry: Application to a cellular toxicokinetic study

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Cui-Li Li, Jiang Ma, Li Zheng, Hui-Jun Li, Ping Li
The emodin-involved hepatotoxicity has been gaining increasing attention. The purpose of the present study was to evaluate the cytotoxicity of emodin on cultured human liver cells (L-02) and predict the possible relation between its cytotoxicity and cellular toxicokinetics. Cell viability and cell damage were assessed by Cell Counting Kit-8 (CCK-8) assay and phase-contrast microscopy, respectively. Cytotoxicity tests demonstrated a concentration- and time-dependent toxic effect of emodin on L-02 cells. Furthermore, emodin at concentration of 30μM led to a significant apoptosis in a time-dependent manner supported by the morphological changes of drug-treated cells. In addition, to elucidate the toxicokinetic characteristics of emodin, a highly sensitive and selective liquid chromatography–mass spectrometry (LC–MS) method was employed and validated for detecting the dynamic alteration of emodin in cells and cell culture media. The proposed method appeared to be suitable for the analysis of emodin with desirable linearity (r ² >0.99), and satisfying precision being less than 8.7%. The range of recoveries of this method was 90.2–101.9%. The preliminary cellular toxicokinetic study revealed a time-dependent intracellular accumulation of emodin, which was consistent with its in vitro toxic effects. These findings confirmed the cytotoxicity of emodin against L-02 cells and displayed the cytotoxic manner of emodin in terms of its cellular uptake and accumulation in L-02 cells.

The effect of anionic surfactant on poliovirus particles during capillary electrophoresis

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Iuliana Oita, Hadewych Halewyck, Bert Thys, Bart Rombaut, Yvan Vander Heyden
Because of its essential role in SDS-PAGE, sodium dodecylsulphate (SDS) is generally associated with protein denaturation. However, for SDS-PAGE, proteins are linearized in the presence of SDS, following the exposure to high temperatures and reducing agents. In comparison, the conditions employed during a capillary electrophoretic (CE) separation involve only a limited exposure to SDS, at much lower temperatures. As the outer surface of the non-enveloped viruses consists of proteins, virus interaction with SDS can be judged from the perspective of SDS–protein interaction. Several studies have indicated that proteins have a different susceptibility to SDS, depending on their secondary structure and number of subunits. Therefore it is not straightforward to estimate what should be expected when intact polioviruses and subviral particles obtained by thermal conversion of the poliovirions, are exposed to SDS during CE separation. In this study it is shown that, during CE separations, SDS has no effect on the integrity of the poliovirion, but the presence of SDS in the separation system influences the poliovirus peak height and shape. The implication of SDS in the CE separation of poliovirus is discussed in detail. On the contrary, the proteinaceous subviral particles, such as the empty capsids, are less stable in the presence of SDS during the CE separation, and aggregates between the individual poliovirus capsid proteins and SDS are formed. Finally, we have proposed an alternative separation approach, involving an SDS gradient, for an improved separation of the subviral particles.

Rapid quantification of tryptophan and tyrosine in chemically defined cell culture media using fluorescence spectroscopy

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Amandine Calvet, Boyan Li, Alan G. Ryder
The rapid and inexpensive analysis of the complex cell culture media used in industrial mammalian cell culture is required for quality and variance monitoring. Excitation-emission matrix (EEM) spectroscopy combined with multi-way chemometrics is a robust methodology applicable for the analysis of raw materials, media, and bioprocess broths. We have shown that the methodology can identify compositional changes and predict the efficacy of media in terms of downstream titer [1]. Here we describe how to extend the measurement methodology for the quantification of tryptophan (Trp), tyrosine (Tyr) in complex chemically defined media. The sample type is an enriched basal RDF medium in which five significant fluorophores were identified: Trp, Tyr, pyridoxine, folic acid, and riboflavin. The relatively high chromophore concentrations and compositional complexity lead to very significant matrix effects which were assessed using PARAllel FACtor analysis2 (PARAFAC2). Taking these effects into account, N-way partial least squares (NPLS) combined with a modified standard addition method was used to build calibration models capable of quantifying Trp and Tyr with errors of ∼4.5 and 5.5% respectively. This demonstrates the feasibility of using the EEM method for the rapid, quantitative analysis of Trp and Tyr in complex cell culture media with minimal sample handling as an alternative to chromatographic based methods.

A full validated hydrophilic interaction liquid chromatography–tandem mass spectrometric method for the quantification of oxaliplatin in human plasma ultrafiltrates

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Hajime Ito, Hiroaki Yamaguchi, Asuka Fujikawa, Nobuaki Tanaka, Ayako Furugen, Kazuaki Miyamori, Natsuko Takahashi, Jiro Ogura, Masaki Kobayashi, Takehiro Yamada, Nariyasu Mano, Ken Iseki
Oxaliplatin is a platinum agent that is used for treatment of colorectal cancer. A sensitive and selective hydrophilic interaction liquid chromatography–tandem mass spectrometric method for the quantification of oxaliplatin was developed. Human plasma ultrafiltrates were precipitated by acetonitrile containing carboplatin as an internal standard and further diluted with acetonitrile. Chromatographic separation of oxaliplatin and the internal standard was achieved with a column modified with phosphorylcholine and an isocratic mobile phase (acetonitrile/water/acetic acid=90:10:0.1, v/v/v) at the flow rate of 0.2mL/min. The lower limit of quantification for oxaliplatin was 25ng/mL. The linearity range of the method was from 25 to 5000ng/mL. The intra-day precision and inter-day precision (RSD) ranged from 0.8 to 6.1%, and the accuracy (RE) was within ±4.5%. The extraction recoveries from human plasma ultrafiltrates were 83.6–91.6%, and ion suppression caused by matrix components was 86.7–88.5% at three different levels, respectively. This method was applied to a clinical pharmacokinetic study of oxaliplatin in a cancer patient. The maximum concentration of colorectal cancer patient administered oxaliplatin was 1650ng/mL.

Simultaneous determination of amlodipine and bisoprolol in rat plasma by a liquid chromatography/tandem mass spectrometry method and its application in pharmacokinetic study

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Huichao Chang, Jinyin Li, Ji Li, Xiaoduo Guan, Fanlu Sun, Zhongzhi Qian, Kaishun Bi, Guorong Fan
A sensitive, specific liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was established for the quantitative determination of amlodipine and bisoprolol, using clenbuterol as the internal standard (IS). The analytes and IS were isolated from 100μL plasma samples by a simple liquid–liquid extraction (LLE). Reverse-phase high performance liquid chromatography (RP-HPLC) separation was accomplished on a Diamonsil C18 column (50mm×4.6mm, 5μm) with a mobile phase composed of methanol–water–formic acid (75:25:0.01, v/v/v) at a flow rate of 0.3mL/min. The method had a chromatographic total run time of 3min. Multiple reacting monitoring (MRM) transitions of m/z [M+H]⁺ 409.1→237.9 (amlodipine), m/z [M+H]⁺ 326.2→116.0 (bisoprolol) and m/z [M+H]⁺ 277.0→203.0 (clenbuterol, IS) were used to quantify amlodipine, bisoprolol and IS, respectively. The method was sensitive with a lower limit of quantitation (LLOQ) of 0.2ng/mL for both amlodipine and bisoprolol, and the linear range was 0.2–50ng/mL for both amlodipine and bisoprolol (r ² >0.9961). All the validation data, such as accuracy, precision and inter-day repeatability, were within the required limits. The method was successfully applied to pharmacokinetic studies of amlodipine and bisoprolol in Sprague–Dawley (SD) rats.

Direct glutathione quantification in human blood by LC–MS/MS: comparison with HPLC with electrochemical detection

16 October 2012, 13:47:21

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volume 71
Isabella Squellerio, Donatella Caruso, Benedetta Porro, Fabrizio Veglia, Elena Tremoli, Viviana Cavalca
Glutathione plays a central role in the defence against oxidative damage and in signaling pathways. Upon oxidation the reduced glutathione (GSH) is transformed to glutathione disulfide (GSSG). The concentration of GSH and GSSG in whole blood samples and their ratios is useful indicator of the oxidative stress status and/or disease risk. Here we describe a liquid-chromatographic method coupled with tandem mass spectrometry (LC–MS/MS) and we present the results of its comparison with a high-performance liquid-chromatographic method with electrochemical detection (HPLC-ECD). The method performed well in terms of validation parameters, i.e. linear range (0.01–50μM for both GSH and GSSG), precision (intra- and inter-day coefficients of variation were less than 10% for both GSH and GSSG), accuracy (bias% varied between −2.1 and 7.9% for both analytes), quantification limits (LLOQs were 0.5μM and 0.0625μM for GSH and GSSG respectively). Furthermore the LC–MS/MS method showed a good agreement with the HPLC-ECD assay. However, major benefits of LC–MS/MS are the improved selectivity, precision and accuracy, the higher sensitivity and the unaltered capacity of detection with time in contrast to ECD.

Highlights

► An LC–MS/MS assay for the determination of GSH and GSSG in whole blood is described. ► The method was compared with an HPLC assay with electrochemical detection (HPLC-ECD). ► LC–MS/MS had higher selectivity and lower variability in comparison with HPLC-ECD. ► The new method allows the quantification of both analytes also in low-concentration samples.