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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 Bhttp://rss.sciencedirect.com/publication/science/7220

Selected papers from the latest issue:

Determination of Cediranib in Mouse Plasma and Brain Tissue Using High-Performance Liquid Chromatography-Mass Spectrometry

29 October 2011, 20:44:15

Publication year: 2011
Source: Journal of Chromatography B, Available online 29 October 2011
Tianli Wang, Rajneet K. Oberoi, William F. Elmquist
A new high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) assay for cediranib, a tyrosine kinase inhibitor for VEGFRs, was developed and validated, for the determination of plasma and brain levels of cediranib in small specimen volumes. Tyrphostin (AG1478) was used as internal standard. Mouse plasma and brain homogenate samples were prepared using liquid-liquid extraction. The assay was validated for a 2.5-2500 ng/mL concentration range for plasma, and for 1-2000 ng/mL range for brain homogenate. For these calibration ranges, within-assay variabilities were 1.1-14.3% for plasma and 1.5-9.4% for brain homogenate; between-assay variabilities were 2.4-9.2% for plasma, and 4.9-10.2% for brain homogenate. Overall accuracy ranged from 101.5 to 107.0% for plasma and 96.5 to 100.2% for brain homogenate, for all target concentrations. The developed assay has been successfully applied for a mouse brain distribution study in mice at an oral dose of 5 mg/kg.

Highlights

► This is the first study to describe a sensitive and precise LC-MS assay for cediranib. ► This assay allows small specimen volumes and adequate detectability to use in tissue distribution studies. ► We have employed the assay in a brain distribution study in the mouse, to examine different mechanisms that limit the CNS distribution of cediranib. ► The assay is generally applicable to a variety of pharmacokinetic and in vitro cell culture experiments

Capillary electrophoretic determination of DNA damage markers: content of 8-hydroxy-2’-deoxyguanosine and 8-nitroguanine in urine

29 October 2011, 20:44:15

Publication year: 2011
Source: Journal of Chromatography B, Available online 29 October 2011
Meng-Jie Li, Jun-Bo Zhang, Wen-Li Li, Qing-Cui Chu, Jian-Nong Ye
A sensitive and low-cost analytical method has been developed to determine 8-hydroxy-2’-deoxyguanosine (8-OHdG) and 8-nitroguanine (8-NO2Gua) based on capillary electrophoresis with amperometric detection (CE-AD) after solid phase extraction (SPE). Under optimized condition, these two markers were well separated from other components coexisting in urine, exhibiting a linear calibration over the concentration range of 0.1–50.0 μg/mL with the detection limits ranging from 0.02 to 0.06 μg/mL. The relative standard deviations (RSDs) were in the range of 0.1% - 2.1% for peak area, 0.1% - 1.5% for migration time, respectively. The average recovery and relative standard deviation (RSD) were within the range of 100.0-108.0% and 0.1-1.7%, respectively. It was found that the urinary contents of 8-OHdG and 8-NO2Gua in cancer patients were significantly higher than those in healthy ones.

Highlights

► 8-OHdG and 8-NO2Gua were simultaneously determined by capillary electrophoresis with amperometric detection (CE-AD). ► CE-AD apparatus employed is inexpensive and easy to operate. ► The proposed method was rather simple and has been applied to analyze clinical samples. ► The excretion levels of urinary 8-OHdG and 8-NO2Gua of cancer patients were significantly higher than those of healthy persons. With the growth of age, 8-OHdG urinary levels also increase slightly.

High-Performance Liquid Chromatography analysis of a novel small-molecule, anti-cancer drug, Palomid 529, in human and mouse plasma and in mouse tissue homogenates

29 October 2011, 20:44:15

Publication year: 2011
Source: Journal of Chromatography B, Available online 29 October 2011
Fan Lin, David Sherris, Jos H. Beijnen, Olaf Van Tellingen
Palomid 529 (8-(1-Hydroxy-ethyl)-2-methoxy-3-(4-methoxy-benzyloxy)-benzo[c]chromen-6-one), is a novel non-steroidal small-molecule drug, which inhibits both mTORC1 and mTORC2 assembly, and elicits both anti-angiogenic and direct anti-tumor effects in vivo. We have developed and validated a sensitive and selective method for the quantification of Palomid 529 in human and mouse plasma and in a range of mouse tissue samples. Sample pretreatment involved liquid-liquid extraction withtert-butyl methyl ether yielding a recovery of >75%. Palomid 529 and the internal standard Palomid 545 were separated using a GraceSmart RP18 column (2.1 × 150 mm) packed with 5 μm C-18 material and a mobile phase comprised of 50% (v/v) acetonitrile and 50% (v/v) water delivered at a flow rate of 0.2 ml/min, and were detected by UV absorbance at a wavelength of 315 nm. Within the linear range of the calibration curve (10 to 10,000 ng/ml), acceptable accuracy and precision was achieved for all tested matrices. The validation results show that the method was selective and reproducible. Palomid 529 was stable in plasma upon 3 repeated freeze-thaw cycles and during storage for up to 24 h at ambient temperature. However, pre-treated samples waiting for HPLC analyses need to be kept under dimmed light conditions at ambient temperature since a significant degradation of both Palomid 529 and Palomid 545 was observed when exposed to light. A pilot pharmacokinetic study in mice demonstrated the applicability of this method for pharmacokinetic purposes. Even at a low dose of 5.4 mg/kg this assay was still sensitive enough to determine the drug concentration in plasma samples obtained up to 24 h after administration.

Highlights

► We describe an HPLC assay for Palomid 529 in human and mouse plasma and tissues. ► Sample pre-treatment involved liquid-liquid extraction withtert-butyl methyl ether. ► Separation involved reversed phase HPLC and detection by UV at 315 nm. ► The dynamic range was 10-10,000 ng/ml. ► The applicability for in vivo pharmacokinetics studies is demonstrated.

Development of a quantification method for digoxin, a typical P-glycoprotein probe in clinical and non-clinical studies, using high performance liquid chromatography-tandem mass spectrometry: The usefulness of negative ionization mode to avoid competitive adduct-ion formation

29 October 2011, 20:44:15

Publication year: 2011
Source: Journal of Chromatography B, Available online 29 October 2011
Hideki Hirabayashi, Hiroshi Sugimoto, Shinichi Matsumoto, Nobuyuki Amano, Toshiya Moriwaki
Highly sensitive and accurate liquid chromatography-tandem mass spectrometry (LC/MS/MS) methods have been developed and validated for measuring digoxin (DGX), a typical P-glycoprotein probe, in human plasma, rat plasma, and rat brain. We extracted DGX and deuterium-labeled DGX (as internal standard) from sample fluids under basic conditions using acetonitrile and sodium chloride-saturated 0.1 mol/L sodium hydroxide. The upper organic layer was diluted with distilled water, and the resulting solution was injected into an LC/MS/MS system in negative ionization mode. Chromatographic separation was achieved on a C18-ODS column in the gradient mobile phase, which comprised of 0.05% (w/v) ammonium carbonate (pH 9.0) and methanol at a flow rate of 0.7 mL/min. Regardless of the type of biological matrix, intra-day and inter-day validation tests demonstrated good linearity of calibration curves within ranges of 0.1 to 10 ng/mL for plasma and 0.5 to 50 ng/g for rat brain and gave excellent accuracy and precision of quality control samples at 4 concentration levels. Unlike existing methods, our approach uses negative ionization to avoid competitive adduct formation of DGX. Our method showed higher sensitivity and wider applicability to various types of biological matrices than existing methods. Our method will support clinical and preclinical investigation ofin vivoP-glycoprotein functionality using DGX.

Highlights

► Highly sensitive and accurate LC/MS/MS method was developed for measuring digoxin. ► The developed method achieved higher sensitivity than previously reported methods requiring only 25 μL of the sample fluid. ► The key successful factor was to employ negative ionization to completely avoid competitive adduct formation. ► The unique, one-step sample pretreatment method may provide advantages over existing methods, such as the small required sample volume, no need for extensive sample cleanup, safety, and low cost of the procedure, among others.

Extractive ethoxycarbonylation in high-temperature gas chromatography-mass spectrometry based analysis of serum estrogens

29 October 2011, 20:44:15

Publication year: 2011
Source: Journal of Chromatography B, Available online 29 October 2011
Ju-Yeon Moon, Se Mi Kang, Myeong Hee Moon, Jongki Hong, Ki Tae Kim, ...
A comprehensive gas chromatography-mass spectrometry (GC-MS)-based profiling was developed as a practical assay for quantification of 18 endogenous estrogens in serum samples. The present GC-MS method was conducted with the two-phase extractive ethoxycarbonlyation (EOC) of the phenolic hydroxy groups of estrogen with ethyl chlorformate combined with the non-polar n-hexane extraction. The subsequent perfluoroacylation of aliphatic hydroxy groups with pentafluoropropionyl anhydride (PFPA) was conducted. The serum samples were separated through a high temperature GC column (MXT-1) within an 8-min run and analyzed in selected-ion monitoring mode with good chromatographic properties for 18 estrogens as their EOC-PFP derivatives. The limit of quantification (LOQ) were 0.025 ∼ 0.10 ng/mL for most estrogens analyzed except for E3 and 2-OH-E3 (0.5 ng/mL each). The devised method was found to be linear over a 10-fold concentration range with a correlation coefficient (r > 0.992), whereas the precision (% CV) and accuracy (% bias) ranged from 3.1 to 16.3% and from 93.5 to 111.1%, respectively. Decreased 2-methoxy-17β-estradiol levels were confirmed in patients with preeclampsia than healthy pregnant women. This technique can be used for a clinical diagnosis as well as understanding the pathogenesis in estrogen-related disorders.

Highlights

► Estrogen metabolism is associated with many hormonal-dependent diseases. ► Estrogens are derivatized with ethoxycarbonylation followed by pentafluoropropionylation. ► Derivatized estrogens are effectively chromatographed by high-temperature GC-MS ► The two-step derivatization gives better selectivity as well as sensitivity in human serum.

Just Published: Chemometrics and Intelligent Laboratory Systems

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:

Chemometrics and Intelligent Laboratory Systems
http://rss.sciencedirect.com/publication/science/5232

Selected papers from the latest issue:

Process monitoring based on mode identification for multi-mode process with transitions

28 October 2011, 20:56:33

Publication year: 2011
Source: Chemometrics and Intelligent Laboratory Systems, Available online 28 October 2011
Fuli Wang, Shuai Tan, Jun Peng, Yuqing Chang
Some industrial processes frequently change due to various factors, such as alterations of feedstocks and compositions, different manufacturing strategies, fluctuations in the external environment and various product specifications. Most multivariate statistical techniques are under the assumption that the process has one nominal operation region. The performance of it is not good when they are used to monitor the process with multiple operation regions. In this paper, we developed an effective approach for monitoring multi-mode continuous processes with the following improvements. 1). Offline mode identification algorithm is proposed to identify (i) stable modes, (ii) transitional modes between two stable modes, (iii) noise. 2). According to the data distribution, proper multivariate statistical algorithm is selected automatically to realize fault detection for each mode. 3). When online monitoring, the right model is chosen based on Mode Transformation Probability (MTP), which makes full use of the empirical knowledge hidden in offline data. This method can enhance real-time performance of online mode identification for continuous process and timely monitoring can be further realized. The proposed method is illustrated by application in furnace temperature system of continuous annealing line. The effectiveness of mode identification and fault detection is demonstrated in the results.

Highlights

► A new mode identification algorithm is firstly proposed for multi-mode continuous process to identify stable modes, transitional modes between two stable modes and noise. ► According to the data distribution, proper multivariate statistical algorithm is selected automatically to realize fault detection for each mode. ► Online mode identification for multi-mode continuous process is realized based on Mode Transformation Probability (MTP), which makes full use of the empirical knowledge hidden in offline data.

The optimal mixture design of experiments: Alternative method in optimizing the aqueous phase composition of a microemulsion

26 October 2011, 20:50:53

Publication year: 2011
Source: Chemometrics and Intelligent Laboratory Systems, Available online 25 October 2011
Zahra Jeirani, Badrul Mohamed Jan, Brahim Si Ali, Ishenny Mohd. Noor, See Chun Hwa, ...
In this paper, an optimum mixture Design of Experiment (DOE) method was used to determine the optimum aqueous phase formulation of a microemulsion. Based on the Design Expert software, a quadratic model was established as a function of the microemulsion component fractions. The model was validated experimentally using an ANOVA table. The diagnostics of the model were also investigated by using Normal Plot of Residuals and Box-Cox Plot. In addition, the effects of the microemulsion component fractions on IFT variation were also studied. Finally, the model was optimized to predict the optimum conditions that would yield minimum IFT. It was observed that the predicted and experimental IFT values at the optimum condition are in good agreement with an error of about 1.5%. The authors concluded that the optimum mixture DOE is reliable and could be used to optimize the composition of a microemulsion system such as enhanced oil recovery (EOR) process.

Highlights

► A model was established as a function of the microemulsion component fractions. ► The model was validated experimentally using an ANOVA table. ► The model was optimized to predict the optimum conditions yielding minimum IFT. ► The predicted and experimental IFT at the optimum condition are in good agreement.

The chemometrics approach applied to FTIR spectral data for analysis of rice bran oil in extra virgin olive oil

26 October 2011, 20:50:53

Publication year: 2011
Source: Chemometrics and Intelligent Laboratory Systems, Available online 25 October 2011
Abdul Rohman, .B. Che Man
Among eleven studied vegetable oils, rice bran oil (RBO) has the close similarity to extra virgin olive oil (EVOO) in terms of FTIR spectra, as shown in the score plot of first and second principal components. The peak intensities at 18 frequency regions were used as matrix variables in principal component analysis (PCA). Consequently, the presence of RBO in EVOO is difficult to detect. This study aimed to use the chemometrics approach, namely discriminant analysis (DA) and multivariate calibrations of partial least square and principle component regression to analyze RBO in EVOO. DA was used for classification of EVOO and EVOO mixed with RBO. Multivariate calibrations were exploited for quantification of RBO in EVOO. The combined frequency regions of 1200 – 900 and 3020 – 3000 cmwere used for such analysis. The results showed that no misclassification was reported for classification of EVOO and EVOO mixed with RBO. Partial least square regression either using normal or first derivative FTIR spectra can be successfully used for quantification of RBO in EVOO. In addition, analysis of fatty acid composition can complement the results obtained from FTIR spectral data.

Highlights

► We used chemometrics for authentication of extra virgin olive oil (EVOO). ► Discriminant analysis classifies EVOO and EVOO adulterated with rice bran oil. ► Partial least square can successfully quantify rice bran oil in EVOO.

A statistical data-processing methodology of Py-GC/MS data for the simulation of flash co-pyrolysis reactor experiments

26 October 2011, 20:50:53

Publication year: 2011
Source: Chemometrics and Intelligent Laboratory Systems, Available online 25 October 2011
Tom Cornelissen, Geert Molenberghs, Maarten Jans, Jan Yperman, Sonja Schreurs, ...
Practically it is extremely difficult to collect observations following a fully sound statistical design, typically encompassing a high number of repetitions, of an intensive and elaborate experimental procedure such as flash pyrolysis reactor experiments. Pyrolysis - gas chromatography / mass spectrometry (Py-GC/MS) is an extremely useful analytical technique in order to simulate a high number of repetitive pyrolysis experiments in an acceptable time span. Combining Py-GC/MS experiments and statistical data processing, conclusions can be drawn on the pyrolysis behaviour of any input material, supplying crucial information on its respective behaviour during the actual flash pyrolysis experiments.In this research Py-GC/MS experiments combined with a tailored statistical data processing methodology strongly indicate the occurrence of synergetic interactions during the flash co-pyrolysis of willow/polyhydroxybutyrate (PHB) blends. Such interactions are also indicated by pattern recognition and by the analysis of the condensable and noncondensable pyrolytic gases obtained from Py-GC/MS. Accordingly, the actual influence of the flash co-pyrolysis of willow and PHB, executed with a semi-continuous pyrolysis reactor, on the pyrolytic oil features is investigated by GC/MS. Based on these experiments an explanation for the observed synergy during flash co-pyrolysis of willow and PHB is proposed.

Highlights

► A full statistical data processing methodology is applied on Py-GC/MS experiments ► Composition changes during co-pyrolysis in various ratios of willow waste and PHB ► Synergy is proved in flash co-pyrolysis of willow waste and PHB in various ratios

Variable Selection for Multifactorial Genomic Data

26 October 2011, 20:50:53

Publication year: 2011
Source: Chemometrics and Intelligent Laboratory Systems, Available online 25 October 2011
Sonia Tarazona, Sonia Prado-López, Joaquín Dopazo, Alberto Ferrer, Ana Conesa
Dimension reduction techniques are used to explore genomic data. Due to the large number of variables (genes) included in this kind of studies, variable selection methods are needed to identify the most responsive genes in order to get a better interpretation of the results or to conduct more specific experiments. These methods should be consistent with the amount of signal in the data. For this purpose, we introduce a novel selection strategy called minAS and also adapt other existing strategies, such us Gamma approximation, resampling techniques, etc. All of them are based on studying the distribution of statistics measuring the importance of the variables in the model. These strategies have been applied to the ASCA-genes analysis framework and more generally to dimension reduction techniques as PCA. The performance of the different strategies was evaluated using simulated data. The best performing methods were then applied on an experimental dataset containing the transcriptomic profiles of human embryonic stem cells cultured under different oxygen concentrations. The ability of the methods to extract relevant biological information from the data is discussed.

Fluidigm technology used to validate new risk loci for Graves disease

Fluidigm Corporation has announced that Rujin Hospital in Shanghai, China has used the company's integrated fluidic circuits (IFCs) to help validate two new susceptibility loci for Graves' disease. Researchers applied the unique properties of the Fluidigm 96.96 Dynamic Array™ IFC and the EP1™ System to re-genotype selected SNPs for the replication study.

In a paper entitled A genome-wide association study identifies two new risk loci for Graves' disease, published in the August 14, 2011 issue of Nature Genetics Magazine, researchers confirmed four previously reported loci and identified two new susceptibility loci for Graves' disease. Graves' disease is a common autoimmune disorder characterized by thyroid stimulating hormone receptor autoantibodies and hyperthyroidism.

To investigate the genetic architecture of Graves' disease, Rujin Hospital researchers conducted a genome-wide association study in 1,536 individuals with Graves' disease (cases) and 1,516 controls. They further evaluated a group of associated SNPs in a second set of 3,994 cases and 3,510 controls. All samples were recruited from the Chinese Han population through collaboration with hospitals in China.

"The Fluidigm EP1 microfluidic genetic analysis system proved to be a powerful tool for SNP genotyping validation research in our GWAS project," noted Dr. Chun-Ming Pan of the State Key Laboratory of Medical Genomics, Ruijin Hospital, Shanghai Jiaotong University School of Medicine. "The EP1 enabled us to easily set up 9,216 PCR experiments at a time without using a robot. Within four hours we acquired almost 10,000 data points with outstanding reproducibility and accuracy. The nanoliter-level reaction chambers of Fluidigm chips resulted in significant cost savings, as we needed to only use minute amounts of the expensive SNP genotyping reagents. For us, the EP1 is an ideal platform for our GWAS research," concluded Dr. Pan.

"There is world-class science being conducted in China and Rujin Hospital's important work in Graves' disease research is a great example of it," said Gajus Worthington, Fluidigm president and chief executive officer. "Fluidigm is proud to have contributed to their discoveries through the use of our genotyping systems, and there is more to come. We now have more than a dozen systems in use within China, at some of the country's leading research laboratories. We believe this is just the beginning and that our technology can play a significant and broad role in enabling China's life science researchers."

GWAS was performed on a microarray system at the Chinese National Human Genome Center in Shanghai, China. In stage 2, 100 SNPs were selected for the replication study. Among them, 96 SNPs were genotyped using TaqMan™ SNP Genotyping Assays using the Fluidigm 96.96 Dynamic Array IFC and EP1 platform.

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:

Enhancing sensitivity and precision on NIR reflectance determination of an API at low concentration: application to an hormonal preparation

29 October 2011, 20:44:55

Publication year: 2011
Source: Journal of Pharmaceutical and Biomedical Analysis, Available online 29 October 2011
J. Arruabarrena, J. Coello, S. Maspoch
The use of a mixed calibration sample set (intact production tablets and powdered doped samples used to enlarge calibration range) is a usual procedure for the NIR reflectance determination of the API content of a pharmaceutical solid preparation. However, the high difference in scattering properties and the intrinsic low sensitivity of NIR make difficult the achievement of a good precision when API is at a low mass proportion (≈1% w/w). The compression of the calibration powdered samples has been studied as a very simple procedure to enhance the sensitivity of NIR reflectance measurements and, consequently, to improve precision. Different pretreatments (SNV, 1D, 2D and their combinations) have been applied to reduce the spectral difference between powdered and compressed samples. Although none eliminates completely this difference, the combined pretreatment SNV + 2D has proved to be the one with a better performance. Results obtained by using both calibration sample sets (powdered and compacted) in the quantification of estradiol valerate (VE, 2 mg/tablet, ≈1.6% w/w) and medroxyprogesterone (MPA, 10 mg ≈ 8% w/w) in intact tablets of the hormonal preparation show that a slight but significant improvement in precision is obtained when using compacted samples for calibration. A HPLC procedure was developed to be used as reference method.

Highlights

► A NIR procedure for the determination of two APIs in an hormone preparation is reported ► A novel procedure to prepare the calibration samples is proposed ► compaction of powdered calibration samples reduce scattering effect ► Compression increases effective optical pathlength and improves precision.

Comparisons of different regressions tools in measurement of antioxidant activity in green tea using near infrared spectroscopy

26 October 2011, 20:40:55

Publication year: 2011
Source: Journal of Pharmaceutical and Biomedical Analysis, Available online 25 October 2011
Quansheng Chen, Zhiming Guo, Jiewen Zhao, Qin Ouyang
To rapidly and efficiently measure antioxidant activity (AA) in green tea, near infrared (NIR) spectroscopy was employed with the help of a regression tool in this work. Three different linear and nonlinear regressions tools (i.e. partial least squares (PLS), back propagation artificial neural network (BP-ANN), and support vector machine regression (SVMR)), were systemically studied and compared in developing the model. The model was optimized by a leave-one-out cross-validation, and its performance was tested according to root mean square error of prediction (RMSEP) and correlation coefficient (Rp) in the prediction set. Experimental results showed that the performance of SVMR model was superior to the others, and the optimum results of the SVMR model were achieved as follow:RMSEP= 0.02161 andRp = 0.9691 in the prediction set. The overall results sufficiently demonstrate that the spectroscopy coupled with the SVMR regression tool has the potential to measure AA in green tea.

Inaccurate data can not be used as standards in pharmaceutical and biomedical analysis

26 October 2011, 20:40:55

Publication year: 2011
Source: Journal of Pharmaceutical and Biomedical Analysis, Available online 25 October 2011
Tadeusz Aniszewski

Comprehensive investigation of the influence of acidic, basic, and organic mobile phase compositions on bioanalytical assay sensitivity in positive ESI mode LC/MS/MS

26 October 2011, 20:40:55

Publication year: 2011
Source: Journal of Pharmaceutical and Biomedical Analysis, Available online 25 October 2011
Paul D. Rainville, Norman W. Smith, David Cowan, Robert S. Plumb
The sensitivity and accuracy of a bioanalytical method is critical in defining the pharmacokinetic (PK) parameters of a potential new chemical entity (NCE). Inhaled therapeutics and low dose NCEs present one of the most significant analytical challenges to the bioanalyst, due to their low systemic concentration. The sensitivity of a bioanalytical LC/MS/MS based assay can be influenced by multiple parameters, including: mobile phase composition, extraction efficiency and chromatographic performance. In this work, we discuss the influence of acidic (pH 3), and basic (pH 10) aqueous mobile phases in conjunction with the two most common organic modifiers used in HPLC, acetonitrile and methanol, on the assay sensitivity of twenty-four probe pharmaceuticals in solvent and biological fluid extract. The study showed that when the test probe pharmaceuticals were analyzed with basic aqueous mobile phases compared to standard acidic conditions the following results were observed: increases in chromatographic peak area ranging from 1.2 to 9.6 fold for twenty-one of the test compounds as well as increased signal-to-noise for greater than seventy percent of the compounds. This observed increase in the MS response was not necessarily related to the later elution of the analyte in a higher organic composition under basic conditions. This was demonstrated as seven out of the twenty-four (approximately thirty percent) of the probe pharmaceuticals tested, eluted earlier, or with the same retention time, under basic conditions, and still produced a greater signal-to-noise when analyzed under these basic conditions. Also observed were decreases in chromatographic peak width, and increases in the retention time of very hydrophilic pharmaceutical compounds. The effect of the mobile phase combinations on the retention and MS response of the choline-containing phospholipids present in precipitated plasma was also investigated, as these analytes are a major source of interference when developing a bioanalytical assay.

Highlights

► The addition of a base, such as ammonium hydroxide, to modify the aqueous mobile phase, has significant benefits to LC/MS/MS based bioanalytical assays under electrospray positive ionization mode. ► An increase in the signal-to-noise was observed for twenty-two out of twenty-four of the probe pharmaceuticals tested with basic compared to traditional acidic mobile phase. ► An increase in the chromatographic retention of poorly retained compounds was observed when utilizing basic mobile phases. ► The increase in the MS response was not necessarily related to the later elution of the analyte in a higher organic composition under basic conditions. ► The phospholipid fraction present in protein precipitated rat plasma was slightly affected by the change in mobile phase pH.

Just Published: Biosensors & Bioelectronics

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:

Biosensors & Bioelectronics
http://rss.sciencedirect.com/publication/science/5223

Selected papers from the latest issue:

An electrochemical aptasensor based on enzyme linked aptamer assay

30 October 2011, 20:44:33

Publication year: 2011
Source: Biosensors and Bioelectronics, Available online 29 October 2011
De-Wen Zhang, Cui-Jin Sun, Fang-Ting Zhang, Li Xu, Ying-Lin Zhou, ...
An aptamer is an artificial functional oligonucleic acid, which can interact with its target molecule with high affinity and specificity. Enzyme linked aptamer assay (ELAA) is developed to detect cocaine using aptamer fragment/cocaine configuration based on the affinity interaction between aptamer fragments with cocaine. The aptasensor was constructed by cleaving anticocaine aptamer into two fragments: one was assembled on a gold electrode surface, while the other was modified with biotin at 3′-end, which could be further labelled with streptavidin-horseradish peroxidase (SA-HRP). Upon binding with cocaine, the HRP-labelled aptamer fragment/cocaine complex formed on the electrode would increase the reduction current of hydroquinone (HQ) in the presence of H2O2. The sensitivity and the specificity of the proposed electrochemical aptasensor were investigated by differential pulse voltammetry (DPV). The results indicated that the DPV signal change could be used to sensitively detect cocaine with the dynamic range from 0.1 μM to 50 μM and the detection limit down to 20 nM (S/N = 3). The proposed aptasensor has the advantages of high sensitivity and low background current. Furthermore, a new configuration for ELAA requiring only a single aptamer sequence is constructed, which can be generalized for detecting different kinds of targets by cleaving the aptamers into two suitable segments.

Highlights

► A simple and sensitive aptasensor for cocaine detection based on enzyme linked aptamer assay (ELAA) using aptamer fragment/target/aptamer fragment configuration is developed. ► The detection limit down to 20 nM for cocaine has been achieved by the reaction of H2O2and HQ catalyzed by HRP. ► The aptasensor shows the potential application in biological fluid. ► A new configuration for ELAA requiring only a single aptamer sequence can be generalized for detecting different kinds of targets.

Antigen-specific T cell phenotyping microarrays using Grating Coupled Surface Plasmon Resonance Imaging and Surface Plasmon Coupled Emission

29 October 2011, 20:44:27

Publication year: 2011
Source: Biosensors and Bioelectronics, Available online 29 October 2011
James M. Rice, Lawrence J. Stern, Ernest F. Guignon, David A. Lawrence, Michael A. Lynes
The circulating population of peripheral T lymphocytes obtained from a blood sample can provide a large amount of information about an individual's medical status and history. Recent evidence indicates that the detection and functional characterization of antigen-specific T cell subsets within the circulating population may provide a diagnostic indicator of disease and has the potential to predict an individual's response to therapy. In this report, a microarray detection platform that combines grating-coupled surface plasmon resonance imaging (GCSPRI) and grating-coupled surface plasmon coupled emission (SPCE) fluorescence detection modalities was used to detect and characterize CD4T cells. The microspot regions of interest (ROIs) printed on the array consisted of immobilized antibodies or peptide loaded MHC monomers (p/MHC) as T cell capture ligands mixed with additional antibodies as cytokine capture ligands covalently bound to the surface of a corrugated gold sensor chip. Using optimized parameters, an unlabelled influenza peptide reactive T cell clone could be detected at a frequency of 0.1% in a mixed T cell sample using GCSPRI. Additionally, after cell binding was quantified, differential TH1 cytokine secretion patterns from a T cell clone cultured under TH1 or TH2 inducing conditions was detected using an SPCE fluorescence based assay. Differences in the secretion patterns of 3 cytokines, characteristic of the inducing conditions, indicated that differences were a consequence of the functional status of the captured cells. A dual mode GCSPRI/SPCE assay can provide a rapid, high content T cell screening/characterization tool that is useful for diagnosing disease, evaluating vaccination efficacy, or assessing responses to immunotherapeutics.

Ultrasensitive and dual functional colorimetric sensors for mercury (II) ions and hydrogen peroxide based on catalytic reduction property of silver nanoparticles

28 October 2011, 20:46:12

Publication year: 2011
Source: Biosensors and Bioelectronics, Available online 28 October 2011
Guang-Li Wang, Xiao-Ying Zhu, Huan-Jun Jiao, Yu-Ming Dong, Zai-Jun Li
The method provides an innovative dual functional sensors for mercury (II) ions and hydrogen peroxide. The addition of H2O2to the mixture of silver nanoparticles (AgNPs) and Hginduced color changes of the solution within several seconds even at 2.0 nM Hg. Other metallic ions could not induce color change even at 10 μM. Of importance, this probe was not only successfully applied to detect Hg, but also it could be used to sense H2O2at a concentration as low as 50 nM (by naked-eye). The outstanding sensitivity and selectivity property for Hgand H2O2resulted from the AgNPs mediated redcution of Hgto elementary Hg in the presence of H2O2, causing the aggregation and colorimetric response of AgNPs. This sensitive and selective colorimetric assay opens up a fresh insight of development facile and fast detection methods for metal ions and biomolecules using the special catalytic reactivity of AgNPs.

Highlights

► Dual functional colorimetric sensors for mercury (II) ions and hydrogen peroxide. ► Hgwas reduced to elementary Hg by silver nanoparticles in the presence of H2O2. ► This method had ultra-high sensitivity and good selectivity

Layer-by-layer self-assembly and electrochemistry: Applications in biosensing and bioelectronics

28 October 2011, 20:46:12

Publication year: 2011
Source: Biosensors and Bioelectronics, Available online 28 October 2011
Rodrigo M. Iost, Frank N. Crespilho
This paper provides an overview of different nanostructured architectures utilised in electrochemical devices and their application in biosensing and bioelectronics. Emphasis is placed on the fabrication of nanostructured films based on a layer-by-layer (LBL) films approach. We discuss the theory and the mechanism of charge transfer in polyelectrolyte multilayer films (PEM), as well as between biomolecules and redox centres, for the development of more sensitive and selective biosensors. Further, this paper presents an overview of topics involving the interaction between nanostructured materials, including metallic nanoparticles and carbon materials, and their effects on the preservation of the activity of biological molecules immobilised on electrode surfaces. This paper also presents examples of biological molecules utilised in film fabrication, such as DNA, several kinds of proteins, and oligonucleotides, and of the role of molecular interaction in biosensing performance. Towards the utilisation of LBL films, examples of several architectures and different electrochemical approaches demonstrate the potential of nanostructured LBL films for several applications that include the diagnosis and monitoring of diseases. Our main aim in this review is to survey what can assist researchers by presenting various approaches currently used in the field of bioelectrochemistry utilising supramolecular architectures based on an LBL approach for application in electrochemical biosensing.

Highlights

► This paper provides an overview of different nanostructured architectures utilised in biosensing and bioelectronics ► We discuss the theory and the mechanism of charge transfer in polyelectrolyte multilayer films ► Examples of several architectures and different electrochemical approaches demonstrate the potential of nanostructured LBL films ► We presents examples of biological molecules utilised in film fabrication, such as DNA, several kinds of proteins, and oligonucleotides, and of the role of molecular interaction in biosensing performance

A CMOS Label-free DNA Sensor using Electrostatic Induction of Molecular Charges

28 October 2011, 20:46:12

Publication year: 2011
Source: Biosensors and Bioelectronics, Available online 28 October 2011
Kang-Ho Lee, Jeong Oen Lee, Sukhwan Choi, Jun-Bo Yoon, Gyu-Hyeong Cho
This paper reports a label-free biosensor for the detection of DNA hybridization. The proposed biosensor measures the surface potential on oligonucleotide modified electrodes using a direct charge accumulation method. The sensor directly and repeatedly measures the charges induced in the working electrode, which correspond to intrinsic negative charges in immobilized molecules. The sensor achieves an improved signal-to-noise ratio (SNR), through the oversampling effect of accumulation for charges and the differential architecture. The sensor also shows stable, robust, and reproducible measurement independent of slight changes in the reference voltage, unlike previous ion-sensitive field effect transistors (ISFETs), providing the benefits of choosing a wide variety of reference electrode materials. The proposed device is integrated with working electrodes, a reference electrode and readout circuits into one package via a 0.35 μm complementary metal-oxide-semiconductor (CMOS) process. The sensor achieves a detectable range of 88.3 dB and a detection limit of 36 μV for surface potential. It is demonstrated that the sensor successfully achieves specific detection of oligonucleotide sequences derived from the H5N1 avian influenza virus. The experiments show a limit of detection of 100 pM and include a single-base mismatch test in 18-mer oligonucleotides.Index Terms- DNA hybridization, negative charge, FET sensor, accumulation

Highlights

► highlight ► We report a label-free biosensor for the detection of DNA hybridization. ► The device measures the surface potential changed by DNA modified electrodes. ► The sensor offers stable, robust and reproducible measurement via CMOS circuits. ► We experiment the specific detection of oligonucleotide from H5N1 virus

Researchers Respond Enthusiastically to Chromatrap Technology

Porvair Filtration Group reports that considerable interest was shown in their novel Chromatrap chromatin immunoprecipitation (ChIP) assay technology recently showcased at the Epigenetics Europe congress in Munich and the Epigenomics of Common Diseases conference held at the Wellcome Trust Conference Centre in Cambridge, UK.

The Porvair Chromatrap spin column approach offers significant advantages compared to methods based on sepharose or magnetic beads, which involve many steps of separation, pipetting and re-suspension. Independent tests with Chromatrap demonstrate levels of DNA pull down up to 25 times higher than with traditional bead based procedures, excellent DNA enrichment with signal-to-noise ratios typically 2 to 3 times better than competing procedures and top performance even with samples with as few as 15,000 cells per assay.

Kevin Quinlan, Business Development Manager for the Chromatrap technology commented "Early adopters of ChromaTrap have been delighted at the increased efficiency and precision they can routinely achieve compared to traditional bead-based ChIP technologies". He added "Many of the pharmaceutical, healthcare and academic researchers we met at the recent congresses highlighted the need for a simpler technology to alleviate problems experienced with current ChIP assays and consequently have committed to evaluate Chromatrap technology". 

For further information please visit http://www.chromatrap.com/ or contact Porvair Filtration Group on +44-1489-864330 /  kevin.quinlan@chromatrap.com.