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:

Automated capillary electrophoresis with on-line preconcentration by solid phase extraction using a sequential injection manifold and contactless conductivity detection

30 April 2012, 09:42:01

Publication year: 2012
Source:Analytica Chimica Acta, Volume 727
Thanh Duc Mai, Benjamin Bomastyk, Hong Anh Duong, Hung Viet Pham, Peter C. Hauser
An extension of a capillary electrophoresis instrument coupled to a sequential injection analysis manifold was developed for automated measurements with on-line solid-phase extraction preconcentration. An in-house built capacitively coupled contactless conductivity detector was employed for sensitive detection with narrow capillaries of 25μm internal diameter. The system was assembled into standardized 19in. frames and racks for easy transport and mobile deployment. The system can be left running unattendedly without manual intervention with good operation stability. To demonstrate the application of the system, a method for the determination of four drugs, namely ibuprofen, diclofenac, naproxen and bezafibrate, was developed with enrichment factors of up to several hundreds. Detection of the drug residues down to the nM-scale was found possible and the method was found suitable for the detection of ibuprofen in the waste water of a hospital in Hanoi.

Graphical Abstract

Graphical abstract Highlights

. ► Robust preconcentration is possible with a syringe-driven sequential injection based manifold. ► Separation of pharmaceutical compounds was done with capillary electrophoresis. ► Contactless conductivity detection (C⁴D) was used for narrow capillaries of 25μm. ► Quantification down to the low nanomolar range was achieved.

An efficient extraction method for quantitation of adenosine triphosphate in mammalian tissues and cells

30 April 2012, 09:42:01

Publication year: 2012
Source:Analytica Chimica Acta, Volume 727
Junji Chida, Kazuhiko Yamane, Tunetomo Takei, Hiroshi Kido
Firefly bioluminescence is widely used in the measurement of adenosine 5′-triphosphate (ATP) levels in biological materials. For such assays in tissues and cells, ATP must be extracted away from protein in the initial step and extraction efficacy is the main determinant of the assay accuracy. Extraction reagents recommended in the commercially available ATP assay kits are chaotropic reagents, trichloroacetic acid (TCA), perchloric acid (PCA), and ethylene glycol (EG), which extract nucleotides through protein precipitation and/or nucleotidase inactivation. We found that these reagents are particularly useful for measuring ATP levels in materials with relatively low protein concentrations such as blood cells, cultured cells, and bacteria. However, these methods are not suitable for ATP extraction from tissues with high protein concentrations, because some ATP may be co-precipitated with the insolubilized protein during homogenization and extraction, and it could also be precipitated by neutralization in the acid extracts. Here we found that a phenol-based extraction method markedly increased the ATP and other nucleotides extracted from tissues. In addition, phenol extraction does not require neutralization before the luciferin–luciferase assay step. ATP levels analyzed by luciferase assay in various tissues extracted by Tris–EDTA–saturated phenol (phenol–TE) were over 17.8-fold higher than those extracted by TCA and over 550-fold higher than those in EG extracts. Here we report a simple, rapid, and reliable phenol–TE extraction procedure for ATP measurement in tissues and cells by luciferase assay.

Graphical Abstract

Graphical abstract Highlights

This study showed that phenol–TE extraction is suitable for measurement of ATP levels in various mammalian tissues (B, brain; H, heart; L, liver; S, spleen; M, muscle) with high protein concentrations and cells, and provided better and more efficient extraction than trichloroacetic acid (TCA) and ethylene glycol (EG), which are recommended in the commercially available ATP assay kits. The ATP levels extracted by phenol–TE were over 17.8-fold higher (depending on tissues) than those in TCA extracts and over 550-fold higher than those in EG extracts. We recommend this method for assay of ATP from mammalian tissues and blood. ► An extraction method for ATP and other nucleotides from mammalian tissues and blood. ► Phenol-based extraction provided better ATP extraction than chaotropic reagents. ► Phenol-based extraction does not require neutralization before the luciferase assay.

Fabrication of novel nanoporous array anodic alumina solid-phase microextraction fiber coating and its potential application for headspace sampling of biological volatile organic compounds

30 April 2012, 09:42:01

Publication year: 2012
Source:Analytica Chimica Acta, Volume 727
Zhuomin Zhang, Qingtang Wang, Gongke Li
In the study, nanoporous array anodic alumina (NAAA) prepared by a simple, rapid and stable two-step anodic oxidization method was introduced as a novel solid-phase microextraction (SPME) fiber coating. The regular nanoporous array structure and chemical composition of NAAA SPME fiber coating was characterized and validated by scanning electron microscopy and energy dispersive spectroscopy, respectively. Compared with the commercial polydimethylsiloxane (PDMS) SPME fiber coating, NAAA SPME fiber coating achieved the higher enrichment capability (1.7–4.7 folds) for the mixed standards of volatile organic compounds (VOCs). The selectivity for volatile alcohols by NAAA SPME fiber coating demonstrated an increasing trend with the increasing polarity of alcohols caused by the gradually shortening carbon chains from 1-undecanol to 1-heptanol or the isomerization of carbon chains of some typical volatile alcohols including 2-ethyl hexanol, 1-octanol, 2-phenylethanol, 1-phenylethanol, 5-undecanol, 2-undecanol and 1-undecanol. Finally, NAAA SPME fiber coating was originally applied for the analysis of biological VOCs of Bailan flower, stinkbug and orange peel samples coupled with gas chromatography–mass spectrometry (GC–MS) detection. Thirty, twenty-seven and forty-four VOCs of Bailan flower, stinkbug and orange peel samples were sampled and identified, respectively. Moreover, the contents of trace 1-octanol and nonanal of real orange peel samples were quantified for the further method validation with satisfactory recoveries of 106.5 and 120.5%, respectively. This work proposed a sensitive, rapid, reliable and convenient analytical method for the potential study of trace and small molecular biological VOCs by the novel NAAA SPME fiber coating.

Graphical Abstract

Graphical abstract Highlights

► Nanoporous array anodic alumina (NAAA) SPME coating was originally prepared. ► NAAA SPME coating achieved excellent enrichment capability and selectivity for VOCs. ► NAAA SPME coating can be applied for the headspace sampling of biological VOCs.

Development of a fiber coating based on molecular sol–gel imprinting technology for selective solid-phase micro extraction of caffeine from human serum and determination by gas chromatography/mass spectrometry

30 April 2012, 09:42:01

Publication year: 2012
Source:Analytica Chimica Acta, Volume 727
Afshin Rajabi Khorrami, Amene Rashidpur
In this work, a molecular sol–gel imprinting approach has been introduced to produce a fiber coating for selective direct immersion solid-phase microextraction (SPME) of caffeine. The polymerization mixture was composed of vinyl trimethoxysilane and methacrylic acid as vinyl sol–gel precursor and functional monomer, respectively. Caffeine was used as template molecule during polymerization process. The prepared fibers could be coupled directly to gas chromatography/mass spectrometry (GC/MS) and used for trace analysis of caffeine in a complex sample such as human serum. The parameters influencing SPME such as time, temperature and stirring speed were optimized. The prepared coating showed good selectivity towards caffeine in the presence of some structurally related compounds. Also, it offered high imprinting capability in comparison to bare fiber and non-imprinted coating. Linear range for caffeine detection was 1–80μgmL⁻¹ and the limit of detection was 0.1μgmL⁻¹. The intra-day and inter-day precisions of the peak areas for five replicates were 10 and 16%, respectively.

Graphical Abstract

Graphical abstract Highlight

► We introduce a molecular sol–gel imprinting approach to produce a fiber coating. ► We used it for selective extraction of caffeine in a SPME procedure. ► Prepared fibers coupled to gas chromatography/mass spectrometry (GC/MS). ► Coating shows promising mechanical and thermal stability, excellent durability, wide linear range and good extraction efficiency. ► The developed fiber is an attractive tool for determination of caffeine in human serum.

An electrochemically enhanced solid-phase microextraction approach based on molecularly imprinted polypyrrole/multi-walled carbon nanotubes composite coating for selective extraction of fluoroquinolones in aqueous samples

30 April 2012, 09:42:01

Publication year: 2012
Source:Analytica Chimica Acta, Volume 727
Xue Liu, Xiaochun Wang, Feng Tan, Hongxia Zhao, Xie Quan, Jingwen Chen, Lianjun Li
In this study, an electrochemically enhanced solid-phase microextraction (EE-SPME) approach based on molecularly imprinted polypyrrole/multi-walled carbon nanotubes (MIPPy/MWCNTs) composite coating on Pt wire was developed for selective extraction of fluoroquinolone antibiotics (FQs) in aqueous samples. During the extraction, a direct current potential was applied to the MIPPy/MWCNTs/Pt fiber as working electrode in a standard three-electrode system, FQ ions suffered electrophoretic transfer to the coating surface and then entered into the shape-complimentary cavities by hydrogen-bonding and ion-exchange interactions. After EE-SPME extraction, the fiber was desorbed with desorption solvent for high-performance liquid chromatography (HPLC) analysis. Some parameters influencing EE-SPME extraction such as applied potential, extraction time, solution pH, ionic strength, and desorption solvent were optimized. EE-SPME showed good selectivity and higher extraction efficiency to FQs compared with that of traditional solid-phase microextraction. EE-SPME coupled with HPLC to determine FQs in water samples, the limits of detection (S/N=3) for the selected FQs are 0.5–1.9μgL⁻¹. The proposed method was successfully used to the analysis of FQs spiked urine and soil samples, with recoveries of 85.1–94.2% for the urine samples and 89.8–95.5% for the soil samples.

Graphical Abstract

Graphical abstract Highlights

► Novel molecularly imprinted polypyrrole/multi-walled carbon nanotubes (MIPPy/MWCNTs) composite coating. ► An electrochemically enhanced solid-phase microextraction (EE-SPME) approach. ► EE-SPME showed good selectivity and high extraction efficiency to fluoroquinolone antibiotics.

Automatic microemulsion preparation for metals determination in fuel samples using a flow-batch analyzer and graphite furnace atomic absorption spectrometry

30 April 2012, 09:42:01

Publication year: 2012
Source:Analytica Chimica Acta, Volume 727
Francisco Antônio S. Cunha, Rafael A. Sousa, David P. Harding, Solange Cadore, Luciano F. Almeida, Mário César U. Araújo
The principal thermodynamic advantages of using microemulsions over standard emulsions for flow metal analysis are the greatly increased analyte stability and emulsive homogeneity that improve both the ease of sample preparation, and the analytical result. In this study a piston propelled flow-batch analyzer (PFBA) for the determination of Cu, Cr and Pb in gasoline and naphtha by graphite furnace atomic absorption spectrometry (GF AAS) was explored. Investigative phase modeling for low dilution was conducted both for gasoline and naphtha microemulsions. Rheological considerations were also explored including a mathematical flow derivation to fine tune the system's operational parameters, and the GF AAS coupling. Both manual and automated procedures for microemulsion preparation were compared. The results of the paired t test at a 95% confidence level showed no significant differences between them. Further recovery test results confirmed a negligible matrix effect of the sample on the analyte absorption signals and an efficient stabilization of the samples (with metals) submitted to microemulsion treatment. The accuracy of the developed procedure was attested by good recovery percentages in the ranges of 100.0±3.5% for Pb in the naphtha samples, and 100.2±3.4% and 100.7±4.6% for Cu and Cr, respectively in gasoline samples.

Graphical Abstract

Graphical abstract Highlights

► Micro-emulsion composition phase study to obtain low fuel dilutions. ► Automated and instantaneous in-line preparation of micro-emulsions for metals determinations. ► A versatile piston-driven form of “Flow-batch Analysis”. ► Rheological considerations explored including a mathematical derivation of flow parameters.

A novel approach to the uniform distribution of liquid in multi-channel (electrochemical) flow-through cells

30 April 2012, 09:42:01

Publication year: 2012
Source:Analytica Chimica Acta, Volume 727
Karel Lacina, Jiří Vondál, Petr Skládal
Four-channel flow-through electrochemical cell working in thin-layer regime was designed, fabricated and characterized experimentally and in computational fluid dynamics (CFD) simulations. The new principle of operation allows reproducible splitting of a stream of liquid into multiple flow channels. Systems comprising of 2-, 3-, 4- and 8-channels were tested. The proper function of the cell is given by the ratio of the cross-sections of the fluidic element collecting chamber and the particular flow paths among which the liquid is distributed. Suitable flow rates providing uniform liquid distribution were evaluated and the results were compared to CFD modeling. The flow-through cells designed according to the proposed principle can be simply incorporated in automated routine analysis as only one inlet and one common outlet are required.

Graphical Abstract

Graphical abstract Highlights

► Novel approach to reliable splitting of the stream of liquid among multiple sensing channels. ► Combination of several channels and a shared output fluidic element-collecting chamber. ► Single inlet and single outlet, complete rejection of cross-talk effects. ► Experimental evaluation of the proposed principle on multi(2,3,4, and 8)-channel arrangements. ► Result verified using computational fluid dynamics (CFD) simulation.

Multiple reaction monitoring-based determination of bovine α-lactalbumin in infant formulas and whey protein concentrates by ultra-high performance liquid chromatography–tandem mass spectrometry using tryptic signature peptides and synthetic peptide standards

30 April 2012, 09:42:01

Publication year: 2012
Source:Analytica Chimica Acta, Volume 727
Jingshun Zhang, Shiyun Lai, Yu Zhang, Baifen Huang, Duo Li, Yiping Ren
The determination of α-lactalbumin in various dairy products attracts wide attention in multidiscipline fields because of its nutritional and biological functions. In the present study, we quantified the bovine α-lactalbumin in various infant formulas and whey protein concentrates using ultra-high performance liquid chromatography coupled to tandem mass spectrometer in multiple reaction monitoring mode. Bovine α-lactalbumin was quantified by employing the synthetic internal standard based on the molar equivalent relationship among the internal standard, bovine α-lactalbumin and their signature peptides. This study especially focused on the recovery rates of the sample preparation procedure and robust quantification of total bovine α-lactalbumin in its native and thermally denatured form with a synthetic internal standard KILDKVGINNYWLAHKALCSE. The observed recovery rates of bovine α-lactalbumin ranged from 95.8 to 100.6% and the reproducibility was excellent (RSD<6%) at different spiking levels. The limit of quantitation is 10mg/100g for infant formulas and whey protein concentrates. In order to validate the applicability of the method, 21 brands of infant formulas were analyzed. The acquired contents of bovine α-lactalbumin were 0.67–1.84g/100g in these infant formulas in agreement with their label claimed values. The experiment of heat treatment time showed that the loss of native α-lactalbumin enhanced with an increasing intensity of heat treatment. Comparing with Ren's previous method by analysis of only native bovine α-lactalbumin, the present method at the peptide level proved to be highly suitable for measuring bovine α-lactalbumin in infant formulas and whey protein concentrates, avoiding forgoing the thermally induced denatured α-lactalbumin caused by the technological processing.

Graphical Abstract

Graphical abstract Highlights

. ► A UHPLC–MS/MS method for quantification of bovine α-lactalbumin was developed. ► Tryptic fragment VGINYWLAHK was chosen as signature peptide of bovine α-lactalbumin. ► An optimal internal standard was designed and synthesized to measure α-lactalbumin. ► It can measure both native and heat thermally induced denatured bovine α-lactalbumin. ► Meet the growing demand to quantify bovine α-lactalbumin in infant formulas and WPC.

Rapid and precise determination of Sr and Nd isotopic ratios in geological samples from the same filament loading by thermal ionization mass spectrometry employing a single-step separation scheme

30 April 2012, 09:42:01

Publication year: 2012
Source:Analytica Chimica Acta, Volume 727
Chao-Feng Li, Xian-Hua Li, Qiu-Li Li, Jing-Hui Guo, Xiang-Hui Li, Yue-Heng Yang
Thermal ionization mass spectrometry (TIMS) offers the excellent precision and accuracy of the Sr and Nd isotopic ratio analysis for geological samples, but this method is labour intensive, expensive and time-consuming. In this study, a new analytical protocol by TIMS is presented that aims at improving analytical efficiency and cutting down experimental cost. Using the single-step cation exchange resin technique, mixed Sr and rare earth elements (REEs) fractions were separated from matrix and evaporated to dryness. Afterwards, mixed Sr+REEs fractions were dissolved and loaded onto the same Re filament using 1μL of 2M HCl. Then, Sr and Nd were sequentially measured without venting using TIMS. In contrast to conventional TIMS methods, the merits of this analytical protocol are its cost- and time-saving adaptations. The applicability of our method is evaluated by replicated measurements of ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd for nine international silicate rock reference materials, spanning a wide range of bulk compositions. The typical internal precision in this study is ca. 0.001% (RSE) for ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd; the analytical results obtained for these standard rocks show a good agreement with reported values, indicating the effectiveness of the proposed method.

Graphical Abstract

Graphical abstract Highlights

Our analytical protocol compared with traditional methods. ► Sr and Nd from the same filament loading were sequentially measured without venting using TIMS. ► This protocol shows a great improvement in the analytical efficiency. ► Experimental costs and labour intensity are significantly cut down.

Lateral flow dipstick test for genotyping of 15 beta-globin gene (HBB) mutations with naked-eye detection

30 April 2012, 09:42:01

Publication year: 2012
Source:Analytica Chimica Acta, Volume 727
Frantzeskos Papanikos, Alexandra Iliadi, Margarita Petropoulou, Penelope C. Ioannou, Theodore K. Christopoulos, Emmanuel Kanavakis, Jan Traeger-Synodinos
For definitive diagnosis of thalassemia carriers and patients, as well as for prenatal diagnosis, genotype analysis is of fundamental importance. We report a dry-reagent, lateral flow dipstick test that enables visual genotyping (detection by naked eye) of 15 mutations common in Mediterranean populations in the beta-globin gene (HBB). The method comprises 3 simple steps: (i) PCR amplification of a single 1896bp segment of the beta globin gene flanking all 15 mutations; (ii) a multiplex (10-plex and/or 30-plex) primer extension reaction of the unpurified amplification product using allele-specific primers. Biotin is incorporated in the extended product; (iii) a dry-reagent multi-allele (10-plex) dipstick assay for visual detection of the primer extension reaction products within minutes. The total time required for PCR, primer extension reaction and the dipstick assay is ∼2h. The method was evaluated by genotyping 45 DNA samples of known genotypes and 54 blind samples. The results were fully concordant with reference methods. The method is simple, rapid, and cost-effective. Detection by the dipstick assay does not require specialized instrumentation or highly qualified personnel. The proposed method could be a particularly useful tool in laboratories with limited resources and a basis for point-of-care diagnostics especially in combination with PCR amplification from whole blood.

Graphical Abstract

Graphical abstract Highlights

► We develop a dipstick test for visual genotyping of 15 beta-globin gene mutations. ► We optimize various parameters affecting the performance of the genotyping test. ► The method was evaluated by analyzing samples of known genotypes and blind samples.

Graphene oxide-based biosensor for sensitive fluorescence detection of DNA based on exonuclease III-aided signal amplification

30 April 2012, 09:42:01

Publication year: 2012
Source:Analytica Chimica Acta, Volume 727
Xu-Hua Zhao, Qiu-Juan Ma, Xiang-Xiang Wu, Xin Zhu
Based on the super fluorescence quenching efficiency of graphene oxide and exonuclease III aided signal amplification, we develop a facile, sensitive, rapid and cost-effective method for DNA detection. In the presence of target DNA, the target-probe hybridization forms a double-stranded structure and exonuclease III catalyzes the stepwise removal of mononucleotides from the blunt 3′ termini of probe, resulting in the recycling of the target DNA and signal amplification. Therefore, our proposed sensor exhibits a high sensitivity towards target DNA with a detection limit of 20pM, which was even lower than previously reported GO-based DNA sensors without enzymatic amplification, and provides a universal sensing platform for sensitive detection of DNA.

Graphical Abstract

Graphical abstract Highlights

We have developed a novel GO-based biosensor for enzymatic amplified DNA detection. By taking advantage of the super fluorescence quenching efficiency of GO and exonuclease III aided signal amplification, our proposed sensor exhibits a high sensitivity towards target DNA with a detection limit of 20pM, which was even lower than previously reported GO-based DNA sensors without enzymatic amplification. Moreover, the sensing system is facile, rapid and cost-effective and can provide a universal sensing platform for sensitive detection of various DNA. ► Graphene oxide (GO) can be prepared in large quantities at very low cost. ► GO can selectively bind and quench a dye-labeled single stranded DNA probe. ► The probe is labeled with a single dye, which reduces the cost for DNA detection. ► Using Exo III can improve the versatility and sensitivity of the DNA assays. ► A sensitive, rapid and cost-effective method for DNA detection has been developed.

Determination of bismuth in open ocean waters by inductively coupled plasma sector-field mass spectrometry after chelating resin column preconcentration

30 April 2012, 09:42:01

Publication year: 2012
Source:Analytica Chimica Acta, Volume 727
Kazuhiro Norisuye, Yoshiki Sohrin
A novel low-blank method is described for the analysis of bismuth in seawater based on preconcentration using an ethylenediaminetriacetic acid chelating resin column followed by determination with inductively coupled plasma sector-field mass spectrometry (ICPSFMS). A sample is siphoned into and drains through the column with the flow rate being kept constant by using a flotation device. Bi in 250mL of acidified seawater is extracted onto the column in this process and eluted with 2mL of 3M HNO3 followed by 3mL of ultra-high purity water. The concentration of Bi in the eluate is measured by ICPMS. The benefits of the method compared to others are its simplicity, a smaller amount of seawater, and lower procedural blanks and detection limits at pgkg⁻¹ levels. Data on dissolved Bi in open ocean reference samples of SAFe and GEOTRACES programs are presented for the first time.

Graphical Abstract

Graphical abstract Highlights

► We introduce a new technique by which solution is siphoned at a constant flow rate. ► We establish a low-blank method for the determination of Bi in open ocean waters. ► The method is based on chelating resin column preconcentration and ICPSFMS. ► The merits of the method are a smaller amount of seawater and high throughput. ► Data on Bi in open ocean reference samples are obtained for the first time.

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Just Published: Spectrochimica Acta Part B: Atomic Spectroscopy

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:

Spectrochimica Acta Part B: Atomic Spectroscopy
http://rss.sciencedirect.com/publication/science/5287

Selected papers from the latest issue:

Surface elemental mapping via glow discharge optical emission spectroscopy

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Gerardo Gamez, Maxim Voronov, Steven J. Ray, Volker Hoffmann, Gary M. Hieftje, Johann Michler
Glow discharge optical emission spectroscopy (GDOES) has evolved in the last couple of decades from direct bulk solid analysis to a high resolution depth-profiling technique. However, the achievable lateral resolution has been historically restricted to the diameter of the sputtered area, i.e. some millimetres. Recently, there has been a push toward characterizing and improving the GDOES limits of lateral resolution. In consequence, a door has been opened for applications to take advantage of the new information dimensions that the technique affords. It is important to sum what has been accomplished so far to clarify the current possibilities and opportunities for development. It will become evident that the data acquisition requirements of GDOES elemental mapping can only be met via spectral imaging. Accordingly, the studies performed to date will be reviewed with emphasis on the spectral imaging geometry that has been utilized.

Ultratrace determination of lead by hydride generation in-atomizer trapping atomic absorption spectrometry: Optimization of plumbane generation and analyte preconcentration in a quartz trap-and-atomizer device

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Jan Kratzer
A compact trap-and-atomizer device and a preconcentration procedure based on hydride trapping in excess of oxygen over hydrogen in the collection step, both constructed and developed previously in our laboratory, were employed to optimize plumbane trapping in this device and to develop a routine method for ultratrace lead determination subsequently. The inherent advantage of this preconcentration approach is that 100% preconcentration efficiency for lead is reached in this device which has never been reported before using quartz or metal traps. Plumbane is completely retained in the trap-and-atomizer device at 290°C in oxygen-rich atmosphere and trapped species are subsequently volatilized at 830°C in hydrogen-rich atmosphere. Effect of relevant experimental parameters on plumbane trapping and lead volatilization are discussed, and possible trapping mechanisms are hypothesized. Plumbane trapping in the trap-and-atomizer device can be routinely used for lead determination at ultratrace levels reaching a detection limit of 0.21ngml^-1 Pb (30s preconcentration, sample volume 2ml). Further improvement of the detection limit is feasible by reducing the blank signal and increasing the trapping time.

Development of an analytical method for the determination of arsenic in gasoline samples by hydride generation-graphite furnace atomic absorption spectrometry

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Emilene M. Becker, Morgana B. Dessuy, Wiliam Boschetti, Maria Goreti R. Vale, Sérgio L.C. Ferreira, Bernhard Welz
The purpose of the present work was to optimize the conditions for the determination of arsenic in gasoline with hydride generation-graphite furnace atomic absorption spectrometry after acid digestion using a full two-level factorial design with center point. The arsine was generated in a batch system and collected in a graphite tube coated with 150μg Ir as a permanent modifier. The sample volume, the pre-reduction conditions, the temperature program and modifier mass were kept fixed for all experiments. The estimated main effects were: reducing agent concentration (negative effect), acid concentration (negative effect) and trapping temperature (positive effect). It was observed that there were interactions between the variables. Moreover, the curvature was significant, indicating that the best conditions were at the center point. The optimized parameters for arsine generation were 2.7molL^-1 hydrochloric acid and 1.6% (w/v) sodium tetrahydroborate. The optimized conditions to collect arsine in the graphite furnace were a trapping temperature of 250°C and a collection time of 30s. The limit of detection was 6.4ngL^-1 and the characteristic mass was 24pg. Two different systems for acid digestion were used: a digester block with cold finger and a microwave oven. The concentration of arsenic found with the proposed method was compared with that obtained using a detergentless microemulsion and direct graphite furnace determination. The results showed that the factorial design is a simple tool that allowed establishing the appropriate conditions for sample preparation and also helped evaluating the interaction between the factors investigated.

Clustering and Training Set Selection Methods for Improving the Accuracy of Quantitative Laser Induced Breakdown Spectroscopy

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Ryan B. Anderson, James F. Bell, Roger C. Wiens, Richard V. Morris, Samuel M. Clegg
We investigated five clustering and training set selection methods to improve the accuracy of quantitative chemical analysis of geologic samples by laser induced breakdown spectroscopy (LIBS) using partial least squares (PLS) regression. The LIBS spectra were previously acquired for 195 rock slabs and 31 pressed powder geostandards under 7Torr CO2 at a stand-off distance of 7m at 17mJ per pulse to simulate the operational conditions of the ChemCam LIBS instrument on the Mars Science Laboratory Curiosity rover. The clustering and training set selection methods, which do not require prior knowledge of the chemical composition of the test-set samples, are based on grouping similar spectra and selecting appropriate training spectra for the partial least squares (PLS2) model. These methods were: (1) Hierarchical clustering of the full set of training spectra and selection of a subset for use in training; (2) K-means clustering of all spectra and generation of PLS2 models based on the training samples within each cluster; (3) Iterative use of PLS2 to predict sample composition and k-means clustering of the predicted compositions to subdivide the groups of spectra; (4) Soft independent modeling of class analogy (SIMCA) classification of spectra, and generation of PLS2 models based on the training samples within each class; (5) Use of Bayesian information criteria (BIC) to determine an optimal number of clusters and generation of PLS2 models based on the training samples within each cluster. The iterative method and the k-means method using 5 clusters showed the best performance, improving the absolute quadrature root mean squared error (RMSE) by ~3 wt. %. The statistical significance of these improvements was ~85%. Our results show that although clustering methods can modestly improve results, a large and diverse training set is the most reliable way to improve the accuracy of quantitative LIBS. In particular, additional sulfate standards and specifically fabricated analog samples with Mars-like compositions may improve the accuracy of ChemCam measurements on Mars. Refinement of the iterative method, modifications of the basic k-means clustering algorithm, and classification based on specifically selected S, C and Si emission lines may also prove beneficial and merit further study.

Application of methane as a gaseous modifier for the determination of silicon using electrothermal atomic absorption spectrometry

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Hans-Joachim Heinrich, Heinrich Kipphardt
For determination of silicon in aqueous solutions by electrothermal atomic absorption spectrometry methane/argon mixtures as a gaseous modifier were applied during the pyrolysis step to improve the analytical performance. The beneficial effects observed on thermal stabilization, signal enhancement and shape of absorbance signals were attributed to the thermal decomposition products of methane, which were hydrogen and carbon black (soot). Using a 5% CH4 mixture with argon, the optimized pyrolysis and atomization temperatures were 1350°C and 2450°C, respectively. A flushing step following the pyrolysis was mandatory to avoid background absorption and accelerated deposition of pyrolytic graphite. Characteristic masses of 50 and 30pg were obtained for standard transverse heated graphite atomizer (THGA) tubes and end-capped THGA tubes, respectively, which were lower than with other previously applied modifiers. A limit of detection of 0.2μgL^-1 (3 s, n =10) has been obtained. In addition, this gaseous modifier did not contribute to contamination which often was significant when a liquid modifier solution was co-injected. The proposed method has been applied to the determination of silicon in ultrapure water, nitric and hydrochloric acids.

The behavior of various chemical forms of nickel in graphite furnace atomic absorption spectrometry under different chemical modification approaches

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Zofia Kowalewska
Various organic and inorganic Ni forms were investigated using graphite furnace atomic absorption spectrometry. Experiments without chemical modification showed a wide range of characteristic mass values for Ni (from 6.7 to 29pg) and the importance of interaction with graphite. With the aim of achieving signal unification of organic Ni forms, different ways of chemical modification were tested. Some rules that govern the behavior of Ni were found and confirmed a significant role of the organic component of the analyte molecule in the analytical process. The application of air as an internal furnace gas in the pyrolysis phase and the Pd modifier injected with the sample solution improved the signal of porphyrins, while the application of iodine and methyltrioctylammonium chloride was required for organic compounds containing oxygen-bound Ni atoms. The Ni signal was strongly diminished when an aqueous solution containing hydrochloric acid was measured with the Pd modifier injected over the sample. Using the developed analytical methods, the range of characteristic mass values for various Ni forms totally dissolved in organic or aqueous solution was 6.5-7.9pg.

Electrochemical generation of volatile lead species using a cadmium cathode: Comparison with graphite, glassy carbon and platinum cathodes

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
María Saénz, Lenys Fernández, José Domínguez, José Alvarado
Working electrodes made out of pyrolytic graphite, glassy carbon, platinum and cadmium were compared for the electrochemical generation of volatile lead species. The same electrolytic cell, using each of the different working electrodes was coupled to an atomic absorption spectrometer and the experimental conditions were optimized in each case, using a univariate approach, to produce the maximum possible amount of volatile lead species. The experiments were focused on the variation of cathode hydrogen overvoltage by the application of a constant current during analysis. Under optimum conditions the performance of the electrochemical hydride generator cell should depend on the cathode material selected due to the different hydrogen overpotential of each material. The lead absorbance signal was taken as a measure of the efficiency of volatile lead species production. Best results were obtained using the Cd cathode, due to its relatively highest hydrogen overpotential, a carrier gas (Ar) flow rate of 55mLmin^-1 an electrolytic current of 0.8 A and a catholyte (HCl) concentration 0.05molL^-1. The analytical figures of merit of the method using the Cd electrode were evaluated and the susceptibility of the method to interferences was assessed by its application to the determination of trace amounts of lead in the presence of the most significant interferents. The calibration curve was linear between 0.5 - 15μgL^-1 Pb. Detection limits and and characteristic mass values were 0.21μgL^-1 and 0.26μgL^-1 respectively. A bovine liver Standard Reference Material and a spiked urine sample were analyzed to check accuracy.

Determination of chlorine in food samples via the AlCl molecule using high-resolution continuum source molecular absorption spectrometry in a graphite furnace

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Miriam Fechetia, André Luiz Tognon, Márcia A.M.S. da Veiga
Determination of chlorine using the molecular absorption of aluminum mono-chloride (AlCl) at the 261.418nm wavelength was accomplished by high-resolution continuum source molecular absorption spectrometry using a transversely heated graphite tube furnace with an integrated platform. For the analysis, 10 μL of the sample followed by 10 μL of a solution containing Al-Ag-Sr modifier, (1gL^-1 each), were directly injected onto the platform. A spectral interference due to the use of Al-Ag-Sr as mixed modifier was easily corrected by the least-squares algorithm present in the spectrometer software. The pyrolysis and vaporization temperatures were 500°C and 2200°C, respectively. To evaluate the feasibility of a simple procedure for the determination of chlorine in food samples present in our daily lives, two different digestion methods were applied, namely (A) an acid digestion method using HNO3 only at room temperature, and (B) a digestion method with Ag, HNO3 and H2O2, where chlorine is precipitated as a low-solubility salt (AgCl), which is then dissolved with ammonia solution. The experimental results obtained with method B were in good agreement with the certified values and demonstrated that the proposed method is more accurate than method A. This is because the formation of silver chloride prevented analyte losses by volatilization. The limit of detection (LOD, 3σ/s) for Cl in methods A and B was 18μgg^-1 and 9μgg^-1, respectively, 1.7 and 3.3 times lower compared to published work using inductively coupled plasma optical emission spectrometry, and absolute LODs were 2.4 and 1.2ng, respectively.

A general Monte Carlo simulation of energy dispersive X-ray fluorescence spectrometers — Part 5 Polarized radiation, stratified samples, cascade effects, M-lines

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Tom Schoonjans, Laszlo Vincze, Vicente Armando Solé, Manuel Sanchez del Rio, Philip Brondeel, Geert Silversmit, Karen Appel, Claudio Ferrero
A general Monte Carlo code for the simulation of energy dispersive X-ray fluorescence (ED-XRF) spectrometers is presented. As a significant extension to existing Monte Carlo codes, dedicated to ED-XRF spectrometers, the new code includes several unique features such as the simulation of M-lines and cascade effects. The detector response function was extended with fluorescence and Compton escape peaks, as well as with pulse pile-up. A full description of the underlying algorithms is given. The software was validated by means of comparison with experimental spectra of standard reference materials collected at the synchrotron XRF-microprobe installed at HASYLAB Beamline L, Hamburg, Germany.

High-resolution continuum source electrothermal atomic absorption spectrometry: Linearization of the calibration curves within a broad concentration range

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Dmitri Katskov, Miranda Hlongwane, Uwe Heitmann, Stefan Florek
The calculation algorithm suggested provides linearization of the calibration curves in high-resolution continuum source electrothermal atomic absorption spectrometry. The algorithm is based on the modification of the function wavelength-integrated absorbance vs. concentration of analyte vapor in the absorption volume. According to the suggested approach, the absorption line is represented by a triangle for low and trapezium for high analyte vapor concentration in the absorption volume. The respective semi-empirical formulas include two linearization parameters, which depend on properties of the absorption line and characteristics of the atomizer and spectrometer. The parameters can be approximately evaluated from the theory and determined in practice from the original broad-range calibration curve. The parameters were found and the proposed calculation algorithm verified in the experiments on direct determination of Ag, Cd, Cu, Fe, Mn and Pb in the solutions within a concentration ranges from 0.15 to 625μg·L⁻¹ using tube, platform tube and filter furnace atomizers. The use of various atomizers, lines, elements and atomization temperatures made possible the simulation of various practical analytical conditions. It was found that the algorithm and optimal linearization parameters made it possible to obtain for each line and atomizer linear approximations of the calibration curves within 3–4 orders of magnitude with correlation coefficients close to 0.999. The algorithm makes possible to employ a single line for the direct element determination over a broad concentration range. The sources of errors and the possibility of a priori theoretical evaluation of the linearization parameters are discussed.

Determination of arsenic and cadmium in crude oil by direct sampling graphite furnace atomic absorption spectrometry

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Alexandre de Jesus, Ariane Vanessa Zmozinski, Isabel Cristina Ferreira Damin, Márcia Messias Silva, Maria Goreti Rodrigues Vale
In this work, a direct sampling graphite furnace atomic absorption spectrometry method has been developed for the determination of arsenic and cadmium in crude oil samples. The samples were weighed directly on the solid sampling platforms and introduced into the graphite tube for analysis. The chemical modifier used for both analytes was a mixture of 0.1% Pd+0.06% Mg+0.06% Triton X-100. Pyrolysis and atomization curves were obtained for both analytes using standards and samples. Calibration curves with aqueous standards could be used for both analytes. The limits of detection obtained were 5.1μgkg⁻¹ for arsenic and 0.2μgkg⁻¹ for cadmium, calculated for the maximum amount of sample that can be analyzed (8mg and 10mg) for arsenic and cadmium, respectively. Relative standard deviations lower than 20% were obtained. For validation purposes, a calibration curve was constructed with the SRM 1634c and aqueous standards for arsenic and the results obtained for several crude oil samples were in agreement according to paired t-test. The result obtained for the determination of arsenic in the SRM against aqueous standards was also in agreement with the certificate value. As there is no crude oil or similar reference material available with a certified value for cadmium, a digestion in an open vessel under reflux using a “cold finger” was adopted for validation purposes. The use of paired t-test showed that the results obtained by direct sampling and digestion were in agreement at a 95% confidence level. Recovery tests were carried out with inorganic and organic standards and the results were between 88% and 109%. The proposed method is simple, fast and reliable, being appropriated for routine analysis.

Direct solid sampling electrothermal atomic absorption spectrometric determination of toxic and potentially toxic elements in certified reference materials of brown coal fly ash

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Peter Török, Mária Žemberyová
This work describes a method for the direct determination of Bi, Cd, Cr, Ni, Pb, Sb, Sn and Zn in reference materials of brown coal fly ash, using solid sampling electrothermal atomic absorption spectrometry. The use of chemical modifiers was found to be necessary for obtaining reproducible and sufficiently sensitive signals for the analytes under study. The mixture of Pd and Mg(NO3)2 was used for the determination of Bi, Cd, Pb, Sb, Sn and Zn, W (permanent modifier) in combination with Mg(NO3)2 (as aqueous modifier) provided well-defined signal profiles for Cr and Ni determination in coal fly ash samples. A systematic study focused on the use of alternative (less sensitive) lines for obtaining sufficient sensitivity. The following analytical lines were used: Bi 306.8nm, Cd 326.1nm, Cr 520.6nm, Ni 305.1nm, Pb 205.3nm, Sb 206.8nm, Sn 300.9nm, Zn 307.6nm. The limits of detection were 0.057μg g⁻¹ for Bi, 0.21μg g⁻¹ for Cd, 1.1μg g⁻¹ for Cr, 1.4μg g⁻¹ for Ni, 4.0μg g⁻¹ for Pb, 0.13μg g⁻¹ for Sb, 0.33μg g⁻¹ for Sn and 16μg g⁻¹ for Zn, respectively.

Characterization of ancient glass excavated in Enez (Ancient Ainos) Turkey by combined Instrumental Neutron Activation Analysis and Fourier Transform Infrared spectrometry techniques

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Sevim Akyuz, Tanil Akyuz, Nuranya M. Mukhamedshina, A. Adiba Mirsagatova, Sait Basaran, Banu Cakan
Ancient glass fragments excavated in the archaeological district Enez (Ancient Ainos)–Turkey were investigated by combined Instrumental Neutron Activation Analysis (INAA) and Fourier Transform Infrared (FTIR) spectrometry techniques. Multi-elemental contents of 15 glass fragments that belong to Hellenistic, Roman, Byzantine, and Ottoman Periods, were determined by INAA. The concentrations of twenty six elements (Na, K, Ca, Sc, Cr, Mn, Fe, Co, Cu, Zn, As, Rb, Sr, Sb, Cs, Ba, Ce, Sm, Eu, Tb, Yb, Lu, Hf, Ta, Au and Th), which might be present in the samples as flux, stabilizers, colorants or opacifiers, and impurities, were examined. Chemometric treatment of the INAA data was performed and principle component analysis revealed presence of 3 distinct groups. The thermal history of the glass samples was determined by FTIR spectrometry.

Direct analysis of silica by means of solid sampling graphite furnace atomic absorption spectrometry

27 April 2012, 09:27:13

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
M. Resano, E. Mozas, C. Crespo, J. Pérez, E. García-Ruiz, M.A. Belarra
This paper reports on the use of solid sampling-graphite furnace atomic absorption spectrometry for the direct analysis of synthetic amorphous silica. In particular, determination of hazardous elements such As, Cd, Cr, Cu, Pb and Sb is investigated, as required by regulations of the food industry. The conclusion of the work is that, after proper optimization of the working conditions, paying particular attention to the atomization temperature and the use of proper modifiers (graphite powder, HNO3 or Pd), it is possible to develop suitable procedures that rely on the use of aqueous standard solutions to construct the calibration curves for all the elements investigated. The proposed method shows important benefits for the cost-effective analysis of such difficult samples in routine labs, permitting fast screening of those elements that are very rarely present in this type of sample, but also accurate quantification of those often found, while offering low limits of detection (always below 0.1mgg⁻¹) that comply well with legal requirements, and precision levels that are fit for the purpose (approx. 6–9% R.S.D.). 

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Just Published: Journal of Chromatography B

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 B
http://rss.sciencedirect.com/publication/science/7220

Selected papers from the latest issue:

Validation of an on-line solid-phase extraction method coupled to liquid chromatography–tandem mass spectrometry detection for the determination of Indacaterol in human serum

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Corinne Emotte, Olivier Heudi, Fanny Deglave, Adrien Bonvie, Laurence Masson, Franck Picard, Animesh Chaturvedi, Tapan Majumdar, Ashish Agarwal, Ralph Woessner, Olivier Kretz
Indacaterol has been recently approved in Europe for the treatment of chronic obstructive pulmonary disease (COPD). In the present study, we have developed and validated a rapid and sensitive on-line solid phase extraction (SPE) method coupled to liquid chromatography–tandem mass spectrometry (LC–MS/MS) detection for the determination of Indacaterol in human serum. The sample preparation involves the serum dilution with a 0.2% acetic acid solution prior to the on-line SPE on a mixed-mode cationic (MCX) polymer based sorbent. The samples were then eluted on a reversed phase column with a mobile phase made of acidified water and methanol and detection was performed by MS using electrospay ionization in positive mode. The analysis time between 2 samples was 7.0min. Standard curves were linear over the range of 10.0pg/mL (LLOQ) to 1000pg/mL with correlation coefficient (r ²) greater than 0.990. The method specificity was demonstrated in six different batches of human serum. Intra-run and inter-run precision and accuracy within ±20% (at the LLOQ) and ±15% (other levels) were achieved during a 3-run validation for quality control samples (QCs). The stability at room temperature (38h) was determined and reported. In addition, the comparison between an off-line SPE procedure and our method gave equivalent results. The results of the present work demonstrated that our on-line SPE–LC–MS/MS method is rapid, sensitive, specific and could be applied to the quantitative analysis of Indacaterol in human serum samples. Our method effectively eliminated the tedious conditioning and rinsing steps associated with conventional off-line SPE and reduced the analysis time. The on-line SPE approach appears attractive for supporting the analysis of several hundreds of clinical samples.

Liquid chromatography–electrospray quadrupole linear ion trap mass spectrometry method for the quantitation of palonosetron in human plasma and urine: Application to a pharmacokinetic study

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Pengfei Li, Ping Ma, Yan Wang, Weihang Tong, Jing Wang, Cheng Wu, Lihong Liu
The new analytical method for the determination of palonosetron in human plasma and urine has been developed based on liquid chromatography–mass spectrometry. The method utilized tramadol as the internal standard (IS). Separation was carried out on a Zorbax Eclipse TC-C18 column using methanol–1mM ammonium formate in water (containing 0.1% formic acid, v/v, pH=2.8) as mobile phase for gradient elution. Detection is carried out by multiple reaction monitoring (MRM) on 3200Qtrap™ mass spectrometry. The method has a chromatographic run time of 5.5min and is linear within the concentration range 0.01–5.00ng/mL for plasma and 0.10–30.00ng/mL for urine both with a LOD of 0.003ng/mL. Intra- and inter-day RSD of the concentration was 3.66–6.60%, 1.29–7.71% for plasma and 2.39–5.76%, 2.06–7.13% for urine. The relative error (RE) was −4.58% to 3.26% for plasma and −1.47% to 2.53% for urine. The recovery rates of palonosetron and IS both for plasma and urine were more than 90%. Palonosetron was stable under all the conditions tested. The method was successfully used to analyze palonosetron in human plasma and urine over a period of 168h after intravenously pumping a single dose of 0.25mg to volunteers. No significant differences were found between the pharmacokinetic parameters and urine accumulated excretory rate for male and female volunteers (P >0.05). A two-compartment model was obtained after administrations. Palonosetron was eliminated at a slow rate in volunteers. The mean urine accumulated excretory rate was 25.97±12.87%. Inter-individual differences could not be neglected due to the high coefficient of variety in several pharmacokinetic parameters and the urine accumulated excretion.

Simultaneous determination of 45 pesticides in fruit and vegetable using an improved QuEChERS method and on-line gel permeation chromatography–gas chromatography/mass spectrometer

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Dasheng Lu, Xinlei Qiu, Chao Feng, Yu’e Jin, Yuanjie Lin, Libei Xiong, Yimin Wen, Dongli Wang, Guoquan Wang
In this study, a method was developed to determine 45 selected pesticides (of different chemical families) in fruit and vegetable (including apple, spinach and cucumber). Samples were extracted using an improved QuEChERS method with salting out and phase separation in two steps. The target pesticides in concentrated extracts were analyzed by an on-line gel permeation chromatography–gas chromatography/mass spectrometer (online-GPC–GC/MS). Online GPC effectively removed matrix interferences and greatly improved the method sensitivity, recoveries and automation. Method limits of quantification were 10ng/g for uniconazole and metalaxyl, and 5ng/g for other 43 target analytes. In three fruit and vegetable matrices each spiked with 45 pesticides (0.01μg/g), mean recoveries ranged from 80 to 118% for most of the tested pesticides except for profenofos (77% in apple) and chlorpyrifos (68% in apple and 75% in cucumber), with relative standard deviations (RSDs) of less than 14%. The results of the proficiency testing showed that the method is very successful in measuring the certified pesticides with less than 1.3 of the absolute value of Z-score. This method has been applied for routinely monitoring pesticides in fresh fruit and vegetable.

Simultaneous determination of flumatinib and its two major metabolites in plasma of chronic myelogenous leukemia patients by liquid chromatography–tandem mass spectrometry

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Yong Yang, Ke Liu, Dafang Zhong, Xiaoyan Chen
Flumatinib is an antineoplastic tyrosine kinase inhibitor used for the treatment of chronic myelogenous leukemia (CML). Its major metabolites in the circulation are N-desmethyl flumatinib (M1) and amide hydrolysis product (M3). To investigate the pharmacokinetics of flumatinib in CML patients, a simple, specific and rapid liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous determination of flumatinib and its two major metabolites in patient plasma. After a simple, one-step protein precipitation with methanol, flumatinib, its two metabolites, and internal standard (HHGV-E) were separated on a C18 column using an isocratic mobile phase of methanol:5mM ammonium acetate:formic acid (60:40:0.4, v/v/v). A total chromatographic run time of 4.2min was achieved. The detection was performed in multiple reaction monitoring mode, using the transitions of m/z 563→ m/z 463 for flumatinib, m/z 549→ m/z 463 for M1, m/z 303→ m/z 175 for M3, and m/z 529→ m/z 429 for HHGV-E. The method was linear over the concentration ranges of 0.400–400ng/mL for flumatinib, 0.100–100ng/mL for M1, and 0.200–200ng/mL for M3, using only 50μL of plasma. The intra- and inter-day precisions were less than 8.5% for flumatinib, 9.8% for M1, and 10.6% for M3 in terms of the relative standard deviation. The accuracy was within ±2.2% for flumatinib, ±6.0% for M1, and ±9.9% for M3 in terms of relative error. The validated method was successfully applied to clinical pharmacokinetic studies of flumatinib mesylate in CML patients following oral administration at all dosage regimens.

Simultaneous determination and pharmacokinetics of protein unbound aspirin and salicylic acid in rat blood and brain by microdialysis: An application to herbal–drug interaction

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Lee-Hsin Shaw, Tung-Hu Tsai
Aspirin is commonly used for the prevention of myocardial infarction and ischemic stroke; whereas the Chinese people employ the bu-yang-huan-wu-tang (BYHWT) as a routine herbal formulation for the treatment and prevention of transient ischemic stroke. The current study develops a microdialysis technique coupled to a validated liquid chromatography system to measure free-form aspirin and salicylic acid for herbal–drug interaction in rat blood and brain. The intra- and inter-day precisions in biological dialysates were within 0.1–9.4% in the concentration ranges of 0.1–50μg/mL and the accuracies ranged from −4.7 to 6.1%. The pharmacokinetic data demonstrate that the area under the concentration time curve (AUC) of the aspirin was 2031±266minμg/mL after aspirin administration (100mg/kg, i.v.). The AUC of salicylic acid was 12660±1799minμg/mL, which suggests that aspirin is quickly hydrolyzed to salicylic acid in blood and the metabolite can also be detected within 15min in brain dialysate. The herbal–drug pharmacokinetic interaction showed no significant effect in blood and brain. The results of pharmacodynamics for the bleeding time suggested that there were no significant differences between the aspirin alone group and the BYHWT pretreated group. However, the bleeding time has been prolonged when compared aspirin alone or the group pretreated with BYHWT to the blank control. The conclusion provides practical information for clinical practice for the herbal formulation BYHWT and aspirin used concurrently.

Multiresidue determination of veterinary drugs in aquaculture fish samples by ultra high performance liquid chromatography coupled to tandem mass spectrometry

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Renata Pereira Lopes, Rocío Cazorla Reyes, Roberto Romero-González, José Luis Martínez Vidal, Antonia Garrido Frenich
A simple, selective and fast multiresidue method was developed for the determination of 32 veterinary drug residues belonging to several families, in gilthead sea bream (Sparus aurata) by ultra high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS). The extraction was based on modified QuEChERS (quick, easy, cheap, effective, rugged and safe) procedure, using as extraction solution a mixture of acetonitrile and methanol (75:25, v/v), and it reduces sample handling, increasing sample throughput in relation to current methodologies. The developed method was validated and mean recovery ranged from 69% to 125% (at 10, 25, 50 and 100μg/kg). Intra and interday precision, estimated as the same levels and expressed as relative standard deviation, RSD, were lower than 20% and 30%, respectively. Limits of detection (LODs) and quantification (LOQs) were lower than 7.5 and 25μg/kg, respectively, except for danofloxacin, oxytetracycline and tetracycline (LOD and LOQ of 15.0 and 50μg/kg, respectively). Decision limit (CCα) and detection capability (CCβ) were also calculated and ranged from 16.7μg/kg (levamisole) to 605.0 (flumequine) μg/kg and from 23.5μg/kg (levamisole) to 611.5μg/kg (flumequine), respectively. The expanded uncertainty, U, was also evaluated ant it was below 25% at 100μg/kg level, except for tetracycline (28%). Finally, the method was applied to ten samples obtained from local supermarkets in Almería (Spain) and traces of some compounds were detected.

On-line two dimensional liquid chromatography/mass spectrometry for the analysis of triacylglycerides in peanut oil and mouse tissue

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Qin Yang, Xianzhe Shi, Qun Gu, Sumin Zhao, Yuanhong Shan, Guowang Xu
Triacylglycerides (TAGs) are a large class of complex neutral lipids that naturally occur in both plants and animals. In the present work, an on-line comprehensive silver-ion liquid chromatography (silver-ion LC)×reversed-phase liquid chromatography (RPLC) system was constructed to analyze these compounds. A micro bore silver-ion modified column was employed in the first dimension with the commonly used hexane-based mobile phase. After a series of C18 columns were assessed, a wide bore column packed with 1.5μm particles was selected as the second dimension column to reduce the negative effect caused by the large volume and strong solvent injection in the second dimension. The system coupled with mass spectrometry was applied to the analysis of an edible peanut oil and a mouse liver extract. Twenty-eight TAGs from the peanut oil and forty-four from the mouse liver were identified based on the TAGs’ retention behaviors on the comprehensive two-dimensional LC system and their APCI MS fragments.

High-sensitivity liquid chromatography–tandem mass spectrometry for the simultaneous determination of five drugs and their cytochrome P450-specific probe metabolites in human plasma

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Kyung-Suk Oh, Su-Jin Park, Dhananjay D. Shinde, Jae-Gook Shin, Dong-Hyun Kim
A sensitive liquid chromatography–tandem mass spectrometric (LC–MS/MS) method with electrospray ionization was developed for the simultaneous quantitation of five probe drugs and their metabolites in human plasma for assessing the in vivo activities of cytochrome P450 (CYP). CYP isoform specific substrates and their metabolites of CYP1A2 (caffeine), CYP2C9 (losartan), CYP2C19 (omeprazole), CYP2D6 (dextromethorphan) and CYP3A (midazolam) were all simultaneously analyzed using LC–MS/MS after administration of a mixture of five drugs (i.e., a “cocktail approach”) to healthy volunteers. The assay uses propranolol as an internal standard; dual liquid extraction; a Xbridge MS C18 (100mm×2.1mm, 3.5μm) column; a gradient mobile phase of 0.1% formic acid/acetonitrile (7/3→3/7); mass spectrometric detection in positive ion mode. The method was validated from 5 to 500ng/mL for caffeine and paraxanthine, 0.1–40ng/mL for losartan and EXP3174, 0.05–20ng/mL for omeprazole and 5-hydroxyomeprazole, 0.008–0.8ng/mL for dextromethorphan and dextrorphan, 0.01–1.0ng/mL for midazolam, and 0.04–4ng/mL for 1′-hydroxymidazolam. The intra- and inter-day precision over the concentration ranges for all analytes were lower than 12.5% and 13.8% (relative standard deviation, %RSD), and accuracy was between 86.5% and 108.4% and between 87.0% and 107.0%, respectively. This highly sensitive and quantitative method allowed a pharmacokinetic study in subjects receiving doses 10–100 times lower than typical therapeutic doses.

Low density solvent based dispersive liquid–liquid microextraction with gas chromatography–electron capture detection for the determination of cypermethrin in tissues and blood of cypermethrin treated rats

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Mohana Krishna Reddy Mudiam, Rajeev Jain, Shailendra Kumar Maurya, Haider A. Khan, Sanghamitra Bandyopadhyay, R.C. Murthy
A simple and rapid method to determine the cypermethrin (CYP) insecticide in rat tissues (kidney, liver and brain) and blood has been developed for the first time using low density solvent-dispersive liquid–liquid microextraction (LDS-DLLME) followed by gas chromatography–electron capture detector (GC–ECD) analysis. Initially, tissue samples containing CYP were homoginized in acetone. Subsequently, homogenate was mixed with n-hexane (extraction solvent) and the mixture was rapidly injected into water. The upper n-hexane layer was collected in a separate microtube and injected into GC–ECD for analysis. Blood samples were diluted with ultrapure water and subjected to DLLME through similar procedure. Parameters such as type and volume of disperser and extraction solvent, salting out effect and extraction time, which can affect the extraction efficiency of DLLME, were optimized. Method was validated by investigating linearity, precision, recovery, limit of detection (LOD) and quantification (LOQ). LODs in tissue were in the range of 0.043–0.314ngmg⁻¹ and for blood it was 8.6ngmL⁻¹ with a signal to noise ratio of 3:1. LOQs in tissue were in the range of 0.143–1.03ngmg⁻¹ and for blood it was 28.3ngmL⁻¹ with a signal to noise ratio of 10:1. Mean recoveries of CYP at three different concentation levels in all the matrices were found to be in the range of 81.6–103.67%. The results show that, LDS-DLLME coupled with GC–ECD offers a simple, rapid and efficient technique for extraction and determination of CYP in rat tissues and blood samples, which in turn would be useful for toxicological studies of CYP.

Residual metals cause variability in methionine oxidation measurements in protein pharmaceuticals using LC-UV/MS peptide mapping

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Li Zang, Tyler Carlage, David Murphy, Ruth Frenkel, Peter Bryngelson, Mark Madsen, Yelena Lyubarskaya
Methionine oxidation has been demonstrated to play an important role in protein stability in vitro and in vivo. It may also cause changes in biological activity and immunogenicity profile of therapeutic proteins. Therefore, it is critical to monitor methionine oxidation in biopharmaceuticals during process and formulation development, as well as long-term stability studies. A common analytical method for methionine oxidation determination is peptide mapping analysis of protein enzymatic digests using UV detection with or without mass spectrometric detection. The quantitation of oxidation is performed based on the UV or extracted ion chromatographic peak areas of the oxidized and non-oxidized peptides. This method was found to be susceptible to significant variability over long-term use. Major factors leading to this variability included presence of low levels of metal ions, especially iron, in the digestion buffer, chromatographic column, LC injector, and other sample contact surfaces. Careful control of metal ion levels generally leads to less variability and long-term consistency of peptide mapping methods for oxidation determination.

Application of high-speed counter-current chromatography coupled with a reverse micelle solvent system to separate three proteins from Momordica charantia

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Yingnan Li, Lianhong Yin, Lingli Zheng, Lina Xu, Youwei Xu, Yanyan Zhao, Yan Qi, Jihong Yao, Xu Han, Kexin Liu, Jinyong Peng
High-speed counter-current chromatography (HSCCC) coupled with a reverse micelle solvent system was successfully developed to separate three proteins from Momordica charantia. Suitable HSCCC conditions were carefully optimized as follows: the stationary phase was a reverse micellar phase composed of isooctane and 50mM bis-(2-ethylhexyl)-1-sulfosuccinate sodium (AOT). The mobile phase contained mobile phase A (50mM Tris–HCl buffer containing 50mM KCl at pH 7.0) for forward-extraction and mobile phase B (50mM Tris–HCl buffer containing 0.5M KCl at pH 10.0) for back-extraction. The flow rate, detection wavelength and column temperature were set at 1.5ml/min, 280nm and 4°C, respectively. Under these conditions, three fractions (I, II and III) were separated, which showed high purity when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The structures of these proteins were then identified by MALDI-TOF/TOF-MS/MS and compared with the NCBInr database. Fractions I and III were identified as resistance-like protein P-B and pentatricopeptide repeat-containing protein, respectively, which were found in M. charantia for the first time. However, fraction II, which is thought to be a new protein, was not identified, and further investigations on this fraction are required. The anticancer activities of these three proteins on the human gastric cancer cell line SGC-7901 were evaluated in vitro. The results indicated that fraction II has excellent anticancer activity (IC50 =0.116mg/ml for 48h treatment). This is the first report on the use of HSCCC to isolate proteins from M. charantia.

Development and validation of a rapid HPLC method for the determination of cefdinir in beagle dog plasma integrated with an automatic on-line solid-phase extraction following protein precipitation in the 96-well plate format

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Ji Li, Li Wang, Zhao Chen, Rui Xie, You Li, Taijun Hang, Guorong Fan
The high-performance liquid chromatography (HPLC) coupled with on-line solid phase extraction (SPE) and ultraviolet (UV) detection was developed for determining cefdinir in beagle dog plasma. After simple pretreatment for plasma with 6% perchloric acid, a volume of 100μL upper layer of the plasma sample was injected into the self-made on-line SPE column. The analytes were retained on the trap column (Lichrospher C18, 4.6mm×37mm, 25μm), and the biological matrix was washed out with the solvent (20mM KH2PO4 adjusted pH 3.0) at flow rate of 2mL/min. By rotation of the switching valve, the target analytes could be eluted from trap column to analytical column in the back-flush mode by the mobile phase (methanol–acetonitrile–20mM KH2PO4 adjusted pH 3.0, 11.25:6.75:82, v/v/v) at flow rate of 1.5mL/min, and then separated on the analytical column (Ultimate™ XB-C18, 4.6mm×50mm, 5μm). The complete cycle of the on-line SPE preconcentration, purification and HPLC separation of the analytes was 4min. The UV detection was performed at 286nm. The calibration curves showed excellent linear relationship (R ² =0.9995) over the concentration range of 0.05–50μg/mL. The optimized method showed good performance in terms of specificity, linearity, detection and quantification limits, precision and accuracy. This method was successfully applied to quantify cefdinir in beagle dog plasma to support the pre-clinical pharmacokinetic trial.

Antibody affinity purification using metallic nickel particles

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Jun Gao, Zhijun Li, Thomas Russell, Zhiyu Li
Functionalized magnetic particles are emerging as a reliable and convenient technique in the purification of biomacromolecules (proteins and nucleic acids) and cell separation. In this study, we used novel solid nickel ferromagnetic particles coated with Protein A for the affinity purification of antibody. The study demonstrated that IgG can be purified from undiluted mouse serum in as few as 5min using Protein A-coated nickel particles. Further, protein crosslinking was shown to stabilize the Protein A on the nickel particle surfaces to minimize Protein A leaching during the affinity purification and elution of IgG. The separation procedure is gentle, scalable, automatable, efficient and economical. By modifying the functional groups of amino acids in the protein coating, crosslinked nickel particles can be used not only for protein affinity purification but for other biological sample preparation and chromatographic applications as well. Methods proposed and tested in this study can be easily modified for small and medium scale antibody purification in lab and pre-clinical research.

High-performance liquid chromatography quadrupole time-of-flight mass spectrometry method for the analysis of antidiabetic drugs in aqueous environmental samples

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Julia Martín, Wolfgang Buchberger, Juan Luis Santos, Esteban Alonso, Irene Aparicio
Antidiabetic compounds are among the most prescribed pharmaceuticals. Nevertheless, their presence in the environment has been scarcely evaluated as there is no method for their determination in environmental samples. This paper reports the development of an analytical method for the determination of traditionally used antidiabetics (metformin and glibenclamide) and novel antidiabetics (vildagliptin, sitagliptin and pioglitazone). The method is based on solid-phase extraction and determination by high-performance liquid chromatography quadrupole time-of-flight mass spectrometry. The method was applied to effluent wastewater, river water and tap water. Mean recoveries of glibenclamide, vildagliptin, sitagliptin and pioglitazone in the matrices evaluated were in the range 78–83%; limits of quantification were in the range 0.4–4.3ngL⁻¹; and precision values were in the range 2.2–13%. The high hydrophilicity and polarity of metformin complicated its simultaneous extraction. Chromabond Tetracycline cartridges and sample pH 8.5 were applied to the extraction of glibenclamide, vildagliptin, sitagliptin and pioglitazone. Oasis HLB cartridges, neutral sample pH and SDS as ion-pair reagent were used for the extraction of metformin. Validation results of metformin were not as favorable as those of the other antidiabetic drugs but were comparable with others previously reported. The developed method was applied to the first-time determination of the concentrations of the five antidiabetic drugs in wastewater, river water and tap water. Metformin was the antidiabetic drug at the highest concentration in wastewater and surface water (up to 253ngL⁻¹ and 104ngL⁻¹, respectively). Two of the antidiabetic drugs of recent prescription, sitagliptin and vildagliptin, were found in effluent wastewater at concentrations of 117ngL⁻¹ and 12ngL⁻¹, respectively, and in river water at concentrations of 35ngL⁻¹ and 6ngL⁻¹, respectively, whereas the classic antidiabetic drug glibenclamide and the novel drug pioglitazone were not detected.

UPLC–MS/MS determination of ractopamine residues in retinal tissue of treated food-producing pigs

26 April 2012, 11:00:04

Publication year: 2012
Source:Journal of Chromatography B, Volumes 895–896
Ana Vulić, Jelka Pleadin, Nina Perši, Dinka Milić, Wolfgang Radeck
Ractopamine is a β2-adrenergic agonist, which reduces fat deposition and promotes muscle growth in animals for meat production. In the European Union countries, systematic monitoring and control of this contaminant residue is regularly performed by use of validated analytical methods of detection in different biological materials. The aim of the present study was to assess persistence of ractopamine in retina as a pigmented tissue by determination of its residues using UPLC–MS/MS as a quantitative confirmatory method after pig exposure to a ractopamine dose of 0.51mg/kg b.w. Experimental group (n =9) of pigs were orally administered ractopamine for 28 days and then randomly sacrificed (n =3) on days 1, 3 and 8 of treatment discontinuation, whereas control animals (n =3) were left untreated. Study results showed mean ractopamine residue concentrations of 110.36μg/kg, 67.11μg/kg and 89.93μg/kg on days 1, 3 and 8 after withdrawal, respectively, indicating high accumulation of ractopamine in retina despite a low dose applied. These data pointed to high affinity of ractopamine for binding to the pigmented segment of the eye, thus supporting the use of pigmented tissues as matrices in the regulatory monitoring of this β2-adrenergic agonist.