High-throughput bioanalytical LC/MS/MS determination of benzodiazepines in human urine: 1000 samples per 12 hours

Determination of hormones in urine by hollow fiber microporous membrane liquid-liquid extraction associated with 96-well plate system and HPLC-FLD detection

In this work, hollow-fiber microporous membrane liquid-liquid extraction (HF-MMLLE) was associated with a 96-well plate system for the determination of estrone, 17-β-estradiol, estriol and 17-α-ethinylestradiol in urine samples. This method exhibited some advantages, such as low cost, easy application, high-throughput and environmentally-friendly aspects. The type of organic solvent to fill the membrane, ionic strength effect, sample dilution, extraction and desorption time, and desorption solvent were examined. After the optimizations, the conditions were comprised of 45 min of extraction, 1-octanol as organic solvent and 15% (w/v) of NaCl; methanol was used as desorption solvent, and the desorption time was fixed at 10 min. The dilution of the sample increased the sensitivity due to the reduction of matrix effects; thus, urine samples were diluted 40-fold. The limits of detection ranged from 0.03 μg L^-1 for 17-β-estradiol to 15 μg L^-1 for estrone, and the limits of quantification ranged from 0.1 μg L^-1 for 17-β-estradiol to 10 μg L^-1 for estrone. The intra-day precision varied from 1.0% for estriol to 13.3% for 17-α-ethinylestradiol, and inter-day precision varied from 7.3% for estrone to 18.1% for estriol. The relative recoveries varied from 82 to 118%.

Fast liquid chromatography method for separation of peptides using a sub-2 μm ground silica monolith packed column

A stationary phase based on sub-2 μm ground silica monolith particles was fabricated by in situ polymerization and applied in micro-column for separation of peptides. The sub-2 μm silica particles were obtained from monolith using sol-gel process followed by grinding and sedimentation to remove the fines. Initially, the silica monolith particles were pretreated with 3-trimethoxysilyl propyl methacrylate to attach double-bonded ligands onto the surface, then a network structure was formed onto the surface of the particle using styrene, N-isopropylacrylamide, and ethylene glycoldimethacrylate. The effect of the flow rate of the mobile phase on the separation performance was investigated. The stationary phase was characterized by field emission scanning electron microscopy, thermogravimetry, particle size distribution, and element analysis. The resultant phase was packed in glass-lined stainless steel micro-columns (2.1 mm × 50 mm) and evaluated for fast separation. An average number of theoretical plates as high as 9800 plates/column (5.10 μm plate height) was achieved for five synthetic peptides under the optimized flow rate of 0.15 mL/min. The repeatabilities of column-to-column, intraday, and interday through relative standard deviation were found better than 4%, exhibiting satisfactory repeatability of the developed micro-column for fast separation of peptides.

Hollow-fiber renewal liquid membrane extraction coupled with 96-well plate system as innovative high-throughput configuration for the determination of endocrine disrupting compounds by high-performance liquid chromatography-fluorescence and diode array detection

This paper describes a new configuration of the hollow fiber renewal liquid membrane (HFRLM) procedure for the high-throughput determination of the endocrine disrupting compounds 4-nonylphenol, 4-octylphenol, 4-tert-octylphenol, methylparaben, ethylparaben and bisphenol A using a 96-well plate system and high-performance liquid chromatography. In this configuration, cylindrical blades were adapted as a support for polypropylene membranes used as supported liquid membranes in the HFRLM approach. The proposed configuration exhibited important advantages including high-throughput, low solvent and sample consumption, and good analytical performance. The optimized extraction conditions were achieved with the use of a mixture comprised of 50:50 v/v 1-octanol:hexane as the supported liquid membrane, sample pH 5, extraction solvent 15 μL (hexane) and extraction time 45 min. The limits of quantification varied from 0.5 μg L^-1 for 4-octylphenol to 15 μg L^-1 for methylparaben and ethylparaben and the r² ranged from 0.9908 for methylparaben to 0.9992 for 4-tert-octylphenol. HFRLM combined with the use of a 96-well plate provides an environmentally-friendly configuration. It offers good accuracy when applied to analyze water samples, with relative recoveries ranging from 72 to 130%, for 4-octylphenol and 4-nonylphenol, respectively, and precision varying from 1 to 14.3%, for 4-nonylphenol at 1.0 μg L^-1 and bisphenol A at 8.0 μg L^-1, respectively.

Biosensor-based engineering of biosynthetic pathways

Biosynthetic pathways provide an enzymatic route from inexpensive renewable resources to valuable metabolic products such as pharmaceuticals and plastics. Designing these pathways is challenging due to the complexities of biology. Advances in the design and construction of genetic variants has enabled billions of cells, each possessing a slightly different metabolic design, to be rapidly generated. However, our ability to measure the quality of these designs lags by several orders of magnitude. Recent research has enabled cells to report their own success in chemical production through the use of genetically encoded biosensors. A new engineering discipline is emerging around the creation and application of biosensors. Biosensors, implemented in selections and screens to identify productive cells, are paving the way for a new era of biotechnological progress.

Use of fast HPLC multiple reaction monitoring cubed for endogenous retinoic acid quantification in complex matrices

Retinoic acid (RA), an essential active metabolite of vitamin A, controls numerous physiological processes. In addition to the analytical challenges owing to its geometric isomers, low endogenous abundance, and often localized occurrence, nonspecific interferences observed during liquid chromatography (LC) multiple reaction monitoring (MRM) quantification methods have necessitated lengthy chromatography to obtain accurate quantification free of interferences. We report the development and validation of a fast high performance liquid chromatography (HPLC) multiplexing multiple reaction monitoring cubed (MRM(3)) assay for selective and sensitive quantification of endogenous RA from complex matrices. The fast HPLC separation was achieved using an embedded amide C18 column packed with 2.7 μm fused-core particles which provided baseline resolution of endogenous RA isomers (all-trans-RA, 9-cis-RA, 13-cis-RA, and 9,13-di-cis-RA) and demonstrated significant improvements in chromatographic efficiency compared to porous particle stationary phases. Multiplexing technology further enhanced sample throughput by a factor of 2 by synchronizing parallel HPLC systems to a single mass spectrometer. The fast HPLC multiplexing MRM(3) assay demonstrated enhanced selectivity for endogenous RA quantification in complex matrices and had comparable analytical performance to robust, validated LC-MRM methodology for RA quantification. The quantification of endogenous RA using the described assay was validated on a number of mouse tissues, nonhuman primate tissues, and human plasma samples. The combined integration of fast HPLC, MRM(3), and multiplexing yields an analysis workflow for essential low-abundance endogenous metabolites that has enhanced selectivity in complex matrices and increased throughput that will be useful in efficiently interrogating the biological role of RA in larger study populations.

Dual LC-MS platform for high-throughput proteome analysis

We describe a dual-column interface for parallel chromatography to improve throughput during LC-MS experimentation. The system employs a high-voltage switch to operate two capillary column/nanospray emitters fixed at the MS orifice. Sequentially loading one column while operating the second nearly doubles the LC-MS duty cycle. Given the innate run-to-run variation of a nanospray LC-MS (12% RSD peak area; 2% retention time), the intercolumn variability of the platform showed no meaningful difference for proteome analysis, with equal numbers of proteins and peptides identified per column. Applied to GeLC analysis of an E. coli extract, throughput was increased using one of three methods: doubling the number of replicates, increasing the LC gradient length, or sectioning the gel into twice as many fractions. Each method increased the total number of identifications as well as detection throughput (number of peptides/proteins identified per hour). The greatest improvement was achieved by doubling the number of gel slices (10 vs 5). Analysis on the dual column platform provided a 26% increase in peptides identified per hour (24% proteins). This translates into ~50% more total proteins and peptides identified in the experiment using the dual LC-MS platform.

Development and validation of an improved LC-MS/MS method for the quantification of desloratadine and its metabolite in human plasma using deutrated desloratadine as internal standard

Purpose:

For the determination of desloratadine (DES) and 3-OH desloratadine (3-OHD) in human plasma using deutrated desloratadine (DESD5) as internal standard (IS), a novel stability indicating liquid chromatography-tandem mass spectrometric method was developed and validated to support the clinical advancement.

Materials and Methods:

The solid-phase extraction method used for sample preparation and calibration range was 100-11,000 pg/ml, for which a quadratic regression (1/x²) was best fitted. The blank plasma was screened and observed free from any endogenous interference.

Results:

The accuracy (% nominal) at low limit of quantification LLOQ level for DES and 3-OHD was 100.4% and 99.9% whereas precision (%CV) was 4.6 and 5.1%. They (DES and 3-OHD) were stable in human plasma after five freeze-thaw cycles, at room temperature for 23.8 hour, bench top stability for 6.4 hour.

Conclusion:

This method fulfills all the regulatory requirements for selectivity, sensitivity, precision, accuracy, stability, goodness of fit, and ruggedness of the method for the determination of DES and 3-OHD in human plasma.

Full utilization of a mass spectrometer using on-demand sharing with multiple LC units

The applicability of liquid chromatography-mass spectrometry (LC/MS) is often limited by throughput. The sharing of a mass spectrometer with multiple LCs significantly improves throughput; however, the reported systems have not been designed to fully utilize the MS duty cycle, and as a result to achieve maximum throughput. To fully utilize the mass spectrometer, the number of LC units that a MS will need to recruit is application dependent and could be significantly larger than the current commercial or published implementations. For the example of a single analyte, the number may approach the peak capacity to a first degree approximation. Here, the construction of a MS system that flexibly recruits any number of LC units demanded by the application is discussed, followed by the method to port a previously developed LC/MS method to the system to fully utilize a mass spectrometer. To demonstrate the performance and operation, a prototypical MS system of eight LC units was constructed. When 1-min chromatographic separations were performed in parallel on the eight LCs of the system, the average LC/MS analysis time per sample was 10.5 s when applied to the analysis of samples in 384-well plate format. This system has been successfully used to conduct large-volume biochemical assays with the analysis of a variety of molecular entities in support of drug discovery efforts. Allowing the recruitment of the number of LC units appropriate for a given application, this system has the potential to be a plug-and-play system to fully utilize a mass spectrometer.

Benzodiazepines: sample preparation and HPLC methods for their determination in biological samples

Benzodiazepines (BDZs) belong to a group of substances known for their sedative, antidepressive, muscle relaxant, tranquilizer, hypnotic and anticonvulsant properties. Their determination in biological fluids is essential in clinical assays as well as in forensics and toxicological studies. Researchers focus on the development of rapid, accurate, precise and sensitive methods for the determination of BDZs and their metabolites. A large number of analytical methods using different techniques have been reported, but none can be considered as the method of choice. BDZs are usually present at trace levels (microgram or nanogram per milliliter) in a complex biological matrix and the potentially interfering compounds must be isolated by various extraction techniques before analysis. An extended and comprehensive review is presented herein, focusing on sample preparation (pretreatment and extraction) and HPLC conditions applied by different authors. These methods enable bioanalysts to achieve detection limits down to 1-2 ng/ml using UV/diode array detection, readily available in most laboratories, and better than 1 ng/ml using electron capture detection, which is lower than that obtained using a nitrogen phosphorus detector. MS interfaced with electrospray ionization offered a similar sensitivity, while negative chemical ionization MS or sonic spray ionization MS provided sensitivity down to 0.1 ng/ml.

Hydrogen/deuterium exchange on aromatic rings during atmospheric pressure chemical ionization mass spectrometry

It has been demonstrated that substituted indoles fully labelled with deuterium on the aromatic ring can undergo substantial exchange back to partial and even fully protonated forms during atmospheric pressure chemical ionisation (APCI) liquid chromatography/mass spectrometry (LC/MS). The degree of this exchange was strongly dependent on the absolute quantity of analyte, the APCI desolvation temperature, the nature of the mobile phase, the mobile phase flow rate and the instrument used. Hydrogen/deuterium (H/D) exchange on several other aromatic ring systems during APCI LC/MS was either undetectable (nitrobenzene, aniline) or extremely small (acetanilide) compared to the effect observed for substituted indoles. This observation has major implications for quantitative assays using deuterium-labelled internal standards and for the detection of deuterium-labelled products from isotopically labelled feeding experiments where there is a risk of back exchange to the protonated form during the analysis.

Automatic Supported Liquid Extraction (SLE) Coupled with HILIC-MS/MS: An Application to Method Development and Validation of Erlotinib in Human Plasma

A novel bioanalytical method was developed and validated for the quantitative determination of erlotinib in human plasma by using the supported liquid extraction (SLE) sample cleanup coupled with hydrophilic interaction liquid chromatography and tandem mass spectrometric detection (HILIC-MS/MS). The SLE extract could be directly injected into the HILIC-MS/MS system for analysis without the solvent evaporation and reconstitution steps. Therefore, the method is simple and rapid. In the present method, erlotinib-d₆ was used as the internal standard. The SLE extraction recovery was 101.3%. The validated linear curve range was 2 to 2,000 ng/mL based on a sample volume of 0.100-mL, with a linear correlation coefficient of > 0.999. The validation results demonstrated that the present method gave a satisfactory precision and accuracy: intra-day CV < 5.9% (.

Measurement of benzodiazepines in urine by liquid chromatography-tandem mass spectrometry: confirmation of samples screened by immunoassay

BACKGROUND

Liquid chromatography linked to tandem mass spectrometry (LC/MS/MS) provides the ability to identify a range of benzodiazepines in accordance with European Union criteria and is an attractive method for the confirmation of benzodiazepines following immunoassay screening.

METHODS

An LC/MS/MS method to detect and quantitate the six most common benzodiazepines/metabolites (diazepam, nitrazepam, nordiazepam, oxazepam, temazepam and 7-aminonitrazepam) was developed together with a qualitative screening method for a further 11 benzodiazepines/metabolites. These methods were used for confirmation of 250 urine samples submitted for routine drug screening by immunoassay for benzodiazepines (100 samples positive for a benzodiazepine, assay cut-off >200 microsg/L).

RESULTS

The lower limits of detection and quantitation were less than 2.5 and 5 microg/L for the six most common benzodiazepines. Recoveries ranged between 97% and 102% and calibration curves were linear to at least 4000 microg/L (r = 0.99). Intra and inter-assay imprecision were <10% (n = 10) and <20% (n = 15), respectively. Confirmation of benzodiazepines using LC/MS/MS was achieved for 89% of the immunoassay-positive urine samples. Of the immunoassay-negative urine samples, 31% of these demonstrated a benzodiazepine using LC/MS/MS.

CONCLUSION

The validated LC/MS/MS method developed is effective for the confirmation of immunoassay screening results for benzodiazepines. The lower limit of detection and assay specificity offers a longer window of detection and more detailed clinical information compared with immunoassay screening.

Application of stable isotope-labeled compounds in metabolism and in metabolism-mediated toxicity studies

Stable isotope-labeled compounds have been synthesized and utilized by scientists from various areas of biomedical research during the last several decades. Compounds labeled with stable isotopes, such as deuterium and carbon-13, have been used effectively by drug metabolism scientists and toxicologists to gain better understanding of drugs' disposition and their potential role in target organ toxicities. The combination of stable isotope-labeling techniques with mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy, which allows rapid acquisition and interpretation of data, has promoted greater use of these stable isotope-labeled compounds in absorption, distribution, metabolism, and excretion (ADME) studies. Examples of the use of stable isotope-labeled compounds in elucidating structures of metabolites and delineating complex metabolic pathways are presented in this review. The application of labeled compounds in mechanistic toxicity studies will be discussed by providing an example of how strategic placement of a deuterium atom in a drug molecule mitigated specific-specific renal toxicity. Other examples from the literature demonstrating the application of stable isotope-labeled compounds in understanding metabolism-mediated toxicities are presented. Furthermore, an example of how a stable isotope-labeled compound was utilized to better understand some of the gene changes in toxicogenomic studies is discussed. The interpretation of large sets of data produced from toxicogenomics studies can be a challenge. One approach that could be used to simplify interpretation of the data, especially from studies designed to link gene changes with the formation of reactive metabolites thought to be responsible for toxicities, is through the use of stable isotope-labeled compounds. This is a relatively unexplored territory and needs to be further investigated. The employment of analytical techniques, especially mass spectrometry and NMR, used in conjunction with stable isotope-labeled compounds to establish and understand mechanistic link between reactive metabolite formation, genomic, and proteomic changes and onset of toxicity is proposed. The use of stable isotope-labeled compounds in early human ADME studies as a way of identifying and possibly quantifying all drug-related components present in systemic circulation is suggested.

Microsome biocolloids for rapid drug metabolism and inhibition assessment by LC-MS

Rat liver microsomes attached to nanoparticles were used for LC-MS studies of CYP3A and 2E1 enzymes in metabolism of N-nitroso compounds. Using these biocolloids, turnover rates were measured within 2 min. Inhibitor IC(50) values for ketoconazole (KET) and 4-methylpyrazole (4-MEP) were estimated.

Mass spectrometry analysis of new chemical entities for pharmaceutical discovery

In this Section, we review the applications of mass spectrometry for the analysis and purification of new chemical entities (NCEs) for pharmaceutical discovery. Since the speed of synthesis of NCEs has dramatically increased over the last few years, new high throughput analytical techniques have been developed to keep pace with the synthetic developments. In this Section, we review both novel, as well as modifications of commonly used mass spectrometry techniques that have helped increase the speed of the analytical process. Part of the review is devoted to the purification of NCEs, which has undergone significant development in recent years, and the close integral association between characterization and purification to drive high throughput operations. At the end of the Section, we review potential future directions based on promising and exciting new developments.

Flexible Automated Approach for Quantitative Liquid Handling of Complex Biological Samples

A fully automated protein precipitation technique for biological sample preparation has been developed for the quantitation of drugs in various biological matrixes. All liquid handling during sample preparation was automated using a Hamilton MicroLab Star Robotic workstation, which included the preparation of standards and controls from a Watson laboratory information management system generated work list, shaking of 96-well plates, and vacuum application. Processing time is less than 30 s per sample or approximately 45 min per 96-well plate, which is then immediately ready for injection onto an LC-MS/MS system. An overview of the process workflow is discussed, including the software development. Validation data are also provided, including specific liquid class data as well as comparative data of automated vs manual preparation using both quality controls and actual sample data. The efficiencies gained from this automated approach are described.

A strategy for high-throughput analysis of levosimendan and its metabolites in human plasma samples using sequential negative and positive ionization liquid chromatography/tandem mass spectrometric detection

Levosimendan (Simdax) is an approved drug in approximately 40 countries and currently in phase III clinical studies in the USA and Europe. An accurate, high-throughput and rugged assay is critical to support these clinical trials. Due to the mechanism of drug metabolism, the drug and its active metabolites often have significant differences in their chemical properties. In order to achieve high assay throughput and low sample volumes, a single bioanalytical assay for the drug and its metabolites is preferred. However, this need may prevent the optimization of both high-performance liquid chromatography (HPLC) and mass spectrometric ionization conditions. The chemical properties of levosimendan are significantly different from those of its two active metabolites, OR-1855 and OR-1896. Here, we present a novel strategy for high-throughput analysis of levosimendan and its metabolites. A 96-well liquid/liquid extraction procedure was developed for sample preparation. A single liquid chromatography/tandem mass spectrometry (LC/MS/MS) system with two separate mobile phases, shared backwash solvent and conditioning solvent, was developed to perform sequential LC separation for levosimendan and the metabolites. Levosimendan was eluted by 5 mM ammonium acetate in 33.3% acetonitrile and detected using negative ionization mode MS/MS monitoring. The metabolites were eluted by 5 mM ammonium acetate and 0.2% acetic acid in 20% acetonitrile and detected with positive ionization mode MS/MS monitoring. The method has been demonstrated to have excellent precision and accuracy, with high assay ruggedness during method validation and clinical sample analysis. The linear dynamic ranges were approximately 200-50,000 pg/mL for levosimendan and approximately 500-130,000 pg/mL for both metabolites. The coefficient of determination (r2) for all analytes was greater than 0.9985. The intra-assay %CVs for QC samples were from 0.9% to 2.0% for levosimendan, 0.9% to 3.2% for OR-1855, and 0.4% to 4.9% for OR-1896. The inter-assay %CVs for QC samples were from 1.2% to 1.8% for levosimendan, 1.3% to 2.7% for OR-1855, and 1.4% to 3.4% for OR-1896. The mean % biases for QC samples were from 1.5% to 5.5% for levosimendan, -1.4% to 2.6% for OR-1855, and -0.3% to 4.5% for OR-1896. By using a single extraction approach coupled with sequential LC/MS/MS analysis for levosimendan and its metabolites, the assay maintained high throughput and low sample volume usage.

Chromatographic behaviour and comparison of column packed with sub-2μm stationary phases in liquid chromatography

In order to reduce the analysis time and maintain good efficiency in liquid chromatography, it is advisable to simultaneously decrease the column length and the particle size of the chromatographic support. Therefore, several manufacturers have developed and commercialized short columns filled with particles that have a diameter smaller than 2 microm. The focus of this work was to check the chromatographic performance of such columns and compare possibilities offered by sub-2 microm supports with conventional columns in terms of analysis time reduction and efficiency improvements. For this purpose, different parameters were discussed namely: separation impedance (E), Knox curves (h,v), and number of plates by time unit (N/t0). Kinetic plots were also drawn. It appeared that sub-2 microm supports were well adapted to improve chromatographic performance and to reduce the analysis time. Furthermore, it was also demonstrated that the best chromatographic performances were reached with high pressure systems (up to 1000 bar).

Liquid Chromatography–Tandem Mass Spectrometry for Detection of Low Concentrations of 21 Benzodiazepines, Metabolites, and Analogs in Urine: Method with Forensic Applications

Background: Commonly used methods for detecting benzodiazepines (BZPs) and BZP-like substances, such as zolpidem and zopiclone, may not detect low concentrations of these drugs. We developed a liquid chromatographic–tandem mass spectrometric method for identifying these drugs and their relevant metabolites.

Methods: We extracted BZPs from urine by solid-phase extraction with a mixed-mode phase (OASIS® HLB cartridges). Chromatographic separation was performed with a Waters XTerra MS C18 [150 × 2.1 mm (i.d.); bead size, 5 μm] reversed-phase column with deuterated analogs of the analytes as internal standards (IS). Detection was performed with a triple-quadruple mass spectrometer that monitored 2 specific transitions per compound in the electrospray, positive-ion selected-reaction monitoring mode. We tested this technique on urine samples from 12 healthy volunteers and 1 forensic sample obtained in a case of alleged drug-facilitated sexual assault.

Results: Chromatographic separation was achieved within 18 min. The linear dynamic ranges extended from 0.02 or 0.1 μg/L (depending on the drug or metabolite) to 50 μg/L. Extraction recovery (range) was 77%–110%. Limits of detection were ≤0.05 μg/L. No ion suppression was seen except for alprazolam, for which baseline decreased by almost 20%. In the forensic urine sample, the method detected alprazolam (3.5 μg/L) and its characteristic metabolite, α-hydroxyalprazolam (0.17 μg/L).

Conclusion: This method measured low concentrations of BZPs and BZP-like substances and might be useful for analyses of urine in suspected drug-facilitated sexual assault cases.

A high-throughput, fully automated liquid/liquid extraction liquid chromatography/mass spectrometry method for the quantitation of a new investigational drug ABT-869 and its metabolite A-849529 in human plasma samples

ABT-869 is a novel ATP-competitive inhibitor for all the vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) receptor tyrosine kinases (RTKs). It is one of the oncology drugs in development at Abbott Laboratories and has great potential for enhanced anti-tumor efficacy as well as activity in a broad range of human cancers. We report here an accurate, precise and rugged liquid chromatography/mass spectrometry (LC/MS/MS) assay for the quantitative measurement of ABT-869 and its acid metabolite A-849529. A fully automated 96-well liquid/liquid extraction method was achieved utilizing a Hamilton liquid handler. The only manual intervention required prior to LC/MS/MS injection is to transfer the 96-well plate to a drying rack to dry the extracts then transfer the plate back to the Hamilton for robotic reconstitution. The linear dynamic ranges were from 1.1 to 598.8 ng/mL for ABT-869 and from 1.1 to 605.8 ng/mL for A-849529. The coefficient of determination (r2) for all analytes was greater than 0.9995. For the drug ABT-869, the intra-assay coefficient of variance (CV) was between 0.4% and 3.7% and the inter-assay CV was between 0.9% and 2.8%. The inter-assay mean accuracy, expressed as percent of theoretical, was between 96.8% and 102.2%. For the metabolite A-849529, the intra-assay CV was between 0.5% and 5.1% and the inter-assay CV was between 0.8% and 4.9%. The inter-assay mean accuracy, expressed as percent of theoretical, was between 96.9% and 100.6%.

Rapid detection and identification of N-acetyl-L-cysteine thioethers using constant neutral loss and theoretical multiple reaction monitoring combined with enhanced product-ion scans on a linear ion trap mass spectrometer

A sensitive and specific liquid chromatography-mass spectrometry (LC-MS) method based on the combination of constant neutral loss scans (CNL) with product ion scans was developed on a linear ion trap. The method is applicable for the detection and identification of analytes with identical chemical substructures (such as conjugates of xenobiotics formed in biological systems) which give common CNLs. A specific CNL was observed for thioethers of N-acetyl-L-cysteine (mercapturic acids, MA) by LC-MS/MS. MS and HPLC parameters were optimized with 16 MAs available as reference compounds. All of these provided a CNL of 129 Da in the negative-ion mode. To assess sensitivity, a multiple reaction monitoring (MRM) mode with 251 theoretical transitions using the CNL of 129 Da combined with a product ion scan (IDA thMRM) was compared with CNL combined with a product ion scan (IDA CNL). An information-dependent acquisition (IDA) uses a survey scan such as MRM (multiple reaction monitoring) to generate "informations" and starting a second acquisition experiment such as a product ion scan using these "informations." Th-MRM means calculated transitions and not transitions generated from an available standard in the tuning mode. The product ion spectra provide additional information on the chemical structure of the unknown analytes. All MA standards were spiked in low concentrations to rat urines and were detected with both methods with LODs ranging from 60 pmol/mL to 1.63 nmol/mL with IDA thMRM. The expected product ion spectra were observed in urine. Application of this screening method to biological samples indicated the presence of a number of MAs in urine of unexposed rats, and resulted in the identification of 1,4-dihydroxynonene mercapturic acid as one of these MAs by negative and positive product ion spectra. These results show that the developed methods have a high potential to serve as both a prescreen to detect unknown MAs and to identify these analytes in complex matrix.

Optimizing an ultrafast generic high-performance liquid chromatography/tandem mass spectrometry method for faster discovery pharmacokinetic sample throughput

For higher throughput screening, where the number of new chemical entities (NCEs) to test is rapidly increasing, fast sample turnaround time is essential. In order to increase efficiency a generic high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) method, with a cycle time of 85 s (42 injections/h), was created. This was accomplished through the use of a 1-min ballistic gradient and the optimization of the autosampler. The gradient was optimized by varying the organic mobile phase concentration and examining its ballistic characteristics with respect to matrix ion suppression and compound retention time. The autosampler time could be reduced by optimizing several parameters and by determining the source of most of the carryover in order to reduce the number of syringe and injector washes. Finally, the reliability of the new generic method is demonstrated by comparison of sample data with a standard 2-min linear gradient method that showed that the data sets were well correlated. For plasma AUC (ng.h/mL) of 28 NCEs, the regression line had a slope of 0.92 and the R2 was 0.929. The described method was found to be useful for both rat plasma and tissue samples.

Automated 96-well solid phase extraction and hydrophilic interaction liquid chromatography–tandem mass spectrometric method for the analysis of cetirizine (ZYRTEC®) in human plasma—with emphasis on method ruggedness

A high-throughput bioanalytical method based on automated sample transfer, automated solid phase extraction, and hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) analysis, has been developed for the determination of cetirizine, a selective H(1)-receptor antagonist. Deuterated cetirizine (cetirizine-d(8)) was synthesized as described and was used as the internal standard. Samples were transferred into 96-well plates using an automated sample handling system. Automated solid phase extraction was carried out using a 96-channel programmable liquid-handling workstation. Solid phase extraction 96-well plate on polymer sorbent (Strata X) was used to extract the analyte. The extracted samples were injected onto a Betasil silica column (50 x 3, 5 microm) using a mobile phase of acetonitrile-water-acetic acid-trifluroacetic acid (93:7:1:0.025, v/v/v/v) at a flow rate of 0.5 ml/min. The chromatographic run time is 2.0 min per injection, with retention time of cetirizine and cetirizine-d(8) both at 1.1 min. The system consisted of a Shimadzu HPLC system and a PE Sciex API 3000 or API 4000 tandem mass spectrometer with (+) ESI. The method has been validated over the concentration range of 1.00-1000 ng/ml cetirizine in human plasma, based on a 0.10-ml sample size. The inter-day precision and accuracy of the quality control (QC) samples demonstrated <3.0% relative standard deviation (R.S.D.) and <6.0% relative error (RE). Stability of cetirizine in stock solution, in plasma, and in reconstitution solution was established. The absolute extraction recovery was 85.8%, 84.5%, and 88.0% at 3, 40, and 800 ng/ml, respectively. The recovery for the internal standard was 84.1%. No adverse matrix effects were noticed for this assay. The automation of the sample preparation steps not only increased the analysis throughput, but also increased method ruggedness. The use of a stable isotope-labeled internal standard further improved the method ruggedness. Practical issues of analyzing incurred samples were discussed. This HILIC-MS/MS method for analysis of citirizine in human plasma was successfully used to support clinical studies.

Comparison of the efficiency of microparticulate and monolithic capillary columns

A comparison is made between the efficiency of microparticulate capillary columns and silica and polymer-based monolithic capillary columns in the pressure-driven (high-performance liquid chromatography) and electro-driven (capillary electrochromatography) modes. With packed capillary columns similar plate heights are possible as with conventional packed columns. However, a large variation is observed in the plate heights for individual columns. This can only be explained by differences in the quality of the packed bed. The minimum plate height obtained with silica monolithic capillary columns in the HPLC mode is approximately 10 microm, which is comparable to that of columns packed with 5-microm particles. The permeability of wide-pore silica monoliths was found to be much higher than that of comparable microparticulate columns, which leads to much lower pressure drops for the same eluent at the same linear mobile phase velocity. For polymer-based monolithic columns (acrylamide, styrene/divinyl benzene, methacrylate, acrylate) high efficiencies have been found in the CEC mode with minimum plate heights between 2 and 10 microm. However, in the HPLC mode minimum plate heights in the range of 10 to 25 microm have been reported.

96-Well liquid–liquid extraction liquid chromatography-tandem mass spectrometry method for the quantitative determination of ABT-578 in human blood samples

We report here a quantitative method for the analysis of ABT-578 in human whole blood samples. Sample preparation was achieved by a semi-automated 96-well format liquid-liquid extraction (LLE) method. Aluminum/polypropylene heat seal foil was used to enclose each well of the 96-well plate for the liquid-liquid extraction. A liquid chromatography combined with tandem mass spectrometry (LC-MS/MS) method with pre-column regeneration was developed for the analysis of sample extracts. Selective reaction monitoring (SRM) of the mass transitions m/z 983-935 and m/z 931-883 was employed for the detection of ABT-578 and internal standard, respectively. The ammonium adduct ions [M + NH(4)](+) generated from electrospray ionization were monitored as the precursor ions. The assay was validated for a linear dynamic range of 0.20-200.75ng/ml. The correlation coefficient (r) was between 0.9959 and 0.9971. The intra-assay CV (%) was between 1.9 and 13.5% and the inter-assay CV (%) was between 4.7 and 11.3%. The inter-assay mean accuracy was between 86.4 and 102.5% of the theoretical concentrations.

Postmortem toxicology of drugs of abuse

Conducting toxicology on post-mortem specimens provides a number of very significant challenges to the scientist. The range of additional specimens include tissues such as decomposing blood and other tissues, hair, muscle, fat, lung, and even larvae feeding on the host require special techniques to isolate a foreign substance and allow detection without interference from the matrix. A number of drugs of abuse are unstable in the post-mortem environment that requires careful consideration when trying to interpret their significance. Heroin, morphine glucuronides, cocaine and the benzodiazepines are particularly prone to degradation. Moreover, redistributive process can significantly alter the concentration of drugs, particularly those with a higher tissue concentration than the surrounding blood. The designer amphetamines, methadone and other potent opioids will increase their concentration in blood post-mortem. These processes together with the development of tolerance means that no concentration of a drug of abuse can be interpreted in isolation without a thorough examination of the relevant circumstances and after the conduct of a post-mortem to eliminate or corroborate relevant factors that could impact on the drug concentration and the possible effect of a substance on the body. This article reviews particular toxicological issues associated with the more common drugs of abuse such as the amphetamines, cannabinoids, cocaine, opioids and the benzodiazepines.

Multicomponent Screening for Drugs of Abuse

By allowing for direct injection of urine, liquid chromatography-tandem mass spectrometry (LC-MS-MS) with atmospheric-pressure chemical ionization has proven to be useful for analysis of drugs of abuse in human urine. The purpose of this study was to evaluate this technique by direct screening for 23 different substances (phenylethylamines, hypnotics, and N-benzylpiperazine) in urine samples. It was possible to achieve lower detection limits compared with commercial immunochemical methods. There was a linear response for all analytes with an intraday coefficient of variation of about 16%, and the gradient elution gave a variability in relative retention time of about 1%. Positive results were confirmed by reanalysis including sample preparation by solid-phase extraction. Among the 529 authentic urine samples analyzed, 35 samples were screened positive for phenylethylamines, and 20 for hypnotics. Of these, 23 (66%) samples were confirmed to be positive for phenylethylamines, and 11 (55%) for hypnotics. This study demonstrates that LC-MS-MS is a valuable complement to immunochemical screening analysis, especially for substances for which immunochemical methods are not yet available or when an increased sensitivity is needed.

Analysis of Benzodiazepines in Dynamically Coated Capillaries by CE-DAD, CE-MS and CE-MS2

The applicability of a low pH volatile electrolyte for fast analysis of benzodiazepines with CE-MS was investigated. The electrolyte is based on a commercially available CEofix buffer system that produces a substantial and highly reproducible electroosmotic flow through a dynamic double coating principle. The system was first evaluated with a mixture of benzodiazepine standards in CE-DAD and the electrolyte composition was further optimized for CE-MS. The LOD for the six selected benzodiazepines with CE-MS was ca. 100 ppb, except for diazepam, for which the LOD was lower than 50 ppb. RSDs varied from 0.51 to 1.02% (n = 7) for migration times and from 4.75 to 11.80% (n = 7) for peak areas. The method was successfully applied to the analysis of a spiked urine sample after solid-phase extraction (SPE). CE-MS2 was performed on a standard mixture.

Monitoring of drugs and metabolites in whole blood by restricted-access solid-phase microextraction coupled to liquid chromatography–mass spectrometry

Robust biocompatible solid-phase microextraction (SPME) devices were prepared using various alkyldiol-silica (ADS) restricted-access materials (RAM) as the SPME coating. The ADS-SPME approach was able to simultaneously fractionate the protein component from a biological sample, while directly extracting diazepam and the major metabolites N-desmethyldiazepam, oxazepam and temazepam, and overcame the present disadvantages of direct sampling in biological matrices by SPME. The devices were interfaced with an LC-MS system and an isocratic mobile phase was used to desorb, separate, and quantify the analytes. The calculated diazepam, nordiazepam, temazepam, and oxazepam detection limits were 20, 20, 30, and 35 ng/ml in heparinized blood, respectively. The method was confirmed to be linear over the range of 50-1000 ng/ml with an average linear coefficient (R2) value of 0.996. The injection repeatability and intra-assay precision of the method were evaluated over ten injections at concentrations of 50, 200, and 500 ng/ml, resulting in a R.S.D. of ca. 10%. The robustness of the ADS-SPME device was evaluated for future use in in vivo studies, providing many direct extractions and subsequent determination of benzodiazepines in blood. For the extraction of the peptides angiotensin I, II, and III from blood, a novel restricted access material with cation exchange properties was evaluated. The ion-exchange diol silica improved the extraction efficiency of peptides relative to the conventional ADS material with reversed phase extraction centers.

Ultra-fast quantitative bioanalysis of a pharmaceutical compound using liquid chromatography-tandem mass spectrometry

This paper describes the ultra-fast determination of a pharmaceutical compound using TurboIonSpray LC-MS-MS on an API 4000 mass spectrometer. Sample preparation consisted of plasma protein precipitation, centrifugation and dilution of the supernatant. The use of small analytical column dimensions (2.1 mm x 10 mm) and high eluent flow rates (up to 2.2 ml/min) in isocratic mode led to a retention time of 9s. A sample-to-sample cycle time of only 10s was achieved by coupling two autosamplers. Partial separation of the drug and its main metabolite could be obtained. The d5-labeled drug used as internal standard compensated for matrix suppression effects. The assay was linear in the concentration range 1-1000 ng/ml, using standards prepared in human plasma. Inter-assay accuracy and precision were 98.5 and 6.2%, respectively. Mean intra-assay accuracy and precision calculated from quality control (QC) samples in human, rat and dog plasma at 3, 30 and 800 ng/ml were 100.8 and 3.8%, respectively. The ultra-fast LC-MS-MS method was successfully cross-validated against a commonly used column-switching LC-MS-MS assay with 2.3 min run time by analyzing real study samples.