Journal of Chromatography B (v.901, #C)

► Simultaneous measurement of metabolites of atrazine in human urine by HPLC–MS/MS. ► 2D HPLC method design based on both pK a and polarity of atrazine derivatives. ► Development of a 2D HPLC method incorporating both SCX–RP and SCX–SCX separation. ► Method validation for application in animal toxicology studies and biomonitoring.Atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] is the most widely used herbicide in the United States. In recent years, there has been controversy about atrazine's potential endocrine/reproductive and neurological adverse effects in wildlife and humans. The controversy triggered several environmental and epidemiologic studies, and it generated needs for sensitive and selective analytical methods for the quantification of atrazine, atrazine metabolites, and degradation or hydrolysis products. We developed a two-dimensional high performance liquid chromatography (2D-HPLC) method with isotope dilution tandem mass spectrometry detection to measure atrazine in urine, along with 11 atrazine metabolites and hydrolysis products, including 6-chloro (Cl), 6-mercapto (Mer) and 6-hydroxy (OH) derivatives, and their desethyl, desisopropyl and diamino atrazine analogs (DEA, DIA and DAA, respectively). The 2D-HPLC system incorporated strong cation exchange and reversed phase separation modes. This versatile approach can be used for the quantitative determination of all 12 compounds in experimental animals for toxicological studies. The method requires only 10 μL of urine, and the limits of detection (LODs) range from 10 to 50 μg/L. The method can also be applied to assess atrazine exposure in occupational settings by measurement of 6-Cl and 6-Mer analogs, which requires only 100 μL of urine with LODs of 1–5 μg/L. Finally, in combination with automated off-line solid phase extraction before 2D-HPLC, the method can also be applied in non-occupational environmental exposure studies for the determination of −6-Cl and 6-Mer metabolites, using 500 μL of urine and LODs of 0.1–0.5 μg/L.
Keywords: Atrazine, 2D-HPLC; Mass spectrometry; Urine; Herbicide;

► NVP-BEZ235 exhibits strong fluorescence properties. ► LLQ of this fluorometric HPLC method is 1 ng/ml. ► NVP-BEZ235 is stable in reconstitution buffer, but unstable in mouse tissue homogenates.NVP-BEZ235 is a novel dual inhibitor of PI3K/mTOR and currently undergoing phase I/II clinical trials for advanced solid tumors. We developed a sensitive and selective reversed-phase high-performance liquid chromatographic (HPLC) assay with fluorometric detection for quantification of NVP-BEZ235 in biological matrices. Liquid–liquid extraction with tert-butyl methyl ether was used for sample pre-treatment, yielding a recovery of >84%. Chromatographic separation of NVP-BEZ235 and the internal standard (IS) NVP-BBD130 was achieved on a GraceSmart C-18 column by isocratic elution with a mobile phase which consisted of acetonitrile, methanol, and milliQ water adjusted with acetic acid to pH 3.7 (20:36:44, v/v/v). Fluorescence detection using excitation and emission wavelengths of 270 and 425 nm, respectively, provided a selectivity and sensitivity allowing quantification down to 1 ng/ml in human plasma and linear calibration curves within a range of 1–1000 ng/ml. The assay was validated for human plasma, mouse plasma and a range of tissues. The accuracy, within-day and between-day precision for all matrices, was within the generally accepted 15% range. NVP-BEZ235 was stable for 72 h in pretreated samples in reconstitution mixture (acetonitrile–water (30:70, v/v)), but unstable in mouse tissue homogenates upon repeated freeze–thaw cycles or long term storage (≥24 h) at room temperature. A pilot pharmacokinetic study in mice demonstrated the applicability of this method for pharmacokinetic purposes. Overall, this assay is suitable for the pharmacokinetic studies of NVP-BEZ235 in mice and in human plasma.
Keywords: Fluorometric detection; HPLC; NVP-BEZ235; NVP-BBD130; PI3K-mTOR inhibitor;

► Developed an entirely solution-based combinative method for membrane proteome analysis. ► Optimized acetone precipitation for sample cleanup and membrane protein recovery. ► Resolved the problems in re-dissolution of acetone-precipitated proteins. ► The developed method can also be used in the analysis of other types of proteins. ► The combinative method is easy to operate at low cost.Although much effort has been made in the field of membrane proteomics, the analysis of membrane proteins particularly integral membrane proteins with poor water solubility still presents a great challenge. In this paper, 2% SDS was used to extract membrane proteins and experimental conditions for the application of acetone precipitation method to the cleanup of SDS-solubilized membrane protein sample were optimized. For improving the re-dissolution and trypsinolysis of acetone-precipitated proteins, several commonly used additives, urea, methanol and sodium deoxycholate (SDC), were employed and compared. The results showed that, when the pre-cooled acetone-to-sample ratio was 6:1 (v/v) with one additional washing step, residual SDS in the protein sample could be lowered to below 0.01% and more than 90% of the proteins were precipitated and therefore recovered. 1% SDC-containing buffer could improve the re-dissolution and digestion of the acetone precipitated proteins more efficiently than the others. Using the combinative sample preparation strategy developed, 398 proteins were identified from the rat liver membrane-enriched fraction, including 188 membrane proteins. Compared with other three representative solution-based sample preparation methods commonly used in membrane proteomics, the newly developed combinative strategy increased the number of identified total proteins and membrane proteins on average by 29.2% and 28.5%, respectively. This combinative strategy was demonstrated to be easily operated at low cost and suitable for the analysis of membrane proteins varying in type and sample volume, etc.
Keywords: Membrane proteome; Sodium dodecyl sulfate; Acetone precipitation; Sodium deoxycholate; In-solution digestion; LC–MS/MS;

Development and validation of an LC–MS/MS method for pharmacokinetic study of methoxyamine in phase I clinical trial by Shuming Yang; Panayiotis Savvides; Lili Liu; Stanton L. Gerson; Yan Xu (25-33).
► An LC–MS/MS method for quantitative determination of methoxyamine in human plasma has been developed and fully validated. ► This method has been applied to pharmacokinetic study of methoxyamine in a phase I clinical trial. ► The concentration–time profiles and pharmacokinetic parameters of methoxyamine in patients were presented.Methoxyamine (MX) is the first DNA base-excision-repair (BER) inhibitor evaluated in humans. This work described the development and validation of an LC–MS/MS method for quantitative determination of MX in human plasma. In this method, MX and its stable isotope methoxyl-d3-amine (MX-d3 as internal standard) were directly derivatized in human plasma with 4-(N,N-diethylamino)benzaldehyde. The derivatized MX and IS were extracted by methyl-tert-butyl ether, and separated isocratically on a Xterra C18 column (2.1 mm × 100 mm) using an aqueous mobile phase containing 45% acetonitrile and 0.4% formic acid at a flow rate of 0.200 ml/min. Quantitation of MX was carried out by multiple-reaction-monitoring (MRM) mode of positive turbo-ion-spray tandem mass spectrometry. This method has been validated according to FDA guidelines for bioanalytical method. The linear calibration range for MX was 1.25–500 ng/ml in human plasma with a correlation coefficient ≥ 0.9993. The intra- and inter-assay precision (%CV) at three concentration levels (3.50, 45.0 and 450 ng/ml) ranged 0.9–1% and 0.8–3%, respectively. The stability studies showed that MX met the acceptable criteria under all tested conditions. The method developed had been applied to the determination of plasma MX concentrations in the first-in-human phase I clinical trial, and PK data were presented.
Keywords: Methoxyamine; Temozolomide; LC–MS/MS; DNA base-excision-repair inhibitor; Pharmacokinetic study;

Comparison of displacement versus gradient mode for separation of a complex protein mixture by anion-exchange chromatography by Robert Ahrends; Björn Lichtner; Friedrich Buck; Diana Hildebrand; Marta Kotasinska; Oliver Kohlbacher; Marcel Kwiatkowski; Moritz Wagner; Maria Trusch; Hartmut Schlüter (34-40).
► Chromatographic separation of a highly complex protein mixture (plasma proteins). ► Comparison gradient versus displacement chromatography. ► Chromatographic separation performance analysis by selective reaction monitoring.Liquid chromatography is often the method of choice for the analysis of proteins in their native state. Nevertheless compared to two-dimensional electrophoresis, the resolution of common chromatographic techniques is low. Liquid chromatography in the displacement mode has previously been shown to offer higher resolution and to elute proteins in the high concentrations. In this study we compared to what extend displacement mode was a suitable alternative to gradient mode for the separation of a complex protein mixture using anion-exchange displacement chromatography and if it is therefore helpful for proteomic investigations. Hence we analyzed the qualitative protein composition of each fraction by tryptic digestion of the proteins, analysis of the tryptic peptides by liquid chromatography coupled to mass spectrometry followed by data base analysis and by measuring the elution profiles of 22 selected proteins with selected reaction monitoring mass spectrometry. In the fractions of displacement mode a significantly higher number of identified proteins (51 versus 16) was yielded in comparison to gradient mode. The resolution of displacement chromatography was slightly lower than of gradient chromatography for many but not for all proteins. The selectivities of displacement mode and gradient mode are very different. In conclusion displacement chromatography is a well suited alternative for top-down proteomic approaches which start with separating intact proteins first prior to mass spectrometric analysis of intact or digested proteins. The significant orthogonality of both modes may be used in the future for combining them in multidimensional fractionation procedures.
Keywords: Displacement chromatography; Protein purification; Selected reaction monitoring; Mass spectrometry; Plasma proteins;

► First application of SPME–GC × GC–TOFMS to the identification of bacterial headspace volatiles. ► Twenty-eight new Pseudomonas aeruginosa headspace volatiles. ► The list of P. aeruginosa headspace volatiles is nearly doubled.Bacteria produce unique volatile mixtures that could be used to identify infectious agents to the species, and possibly the strain level. However, due to the immense variety of human pathogens, and the close relatedness of some of these bacteria, the robust identification of the bacterium based on its volatile metabolome is likely to require a large number of volatile compounds for each species. We applied comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry (GC × GC–TOFMS) to the identification of the headspace volatiles of Pseudomonas aeruginosa PA14 grown for 24 h in lysogeny broth. This is the first reported use of GC × GC–TOFMS for the characterization of bacterial headspace volatiles. The analytical purity that is afforded by this chromatographic method facilitated the identification of 28 new P. aeruginosa-derived volatiles, nearly doubling the list of volatiles for this species.
Keywords: GC × GC–TOFMS; SPME; Pseudomonas aeruginosa; Bacterial volatiles; Metabolomics;

► A chromatography effect has been observed leading to assay bias. ► 50 μL spot volume recommended for saturating the paper and maintaining accuracy. ► Significantly higher measured [25OHD3] in spots punched out from the periphery. ► Paper type to be standardised for sample collection in prospective studies using DBS.Dried blood spots (DBS) are a convenient collection and archiving method for blood specimens. The interest in screening certain analytes in neonatal DBS continues to increase for a variety of paediatric disorders. 25-Hydroxyvitamin D3 (25OHD3) is one such analyte. We investigated potential factors that may affect the analysis of 25OHD3 in prospective cohorts of DBS, such as blood spot volume, hole punch position, and paper type. All of these factors were shown to affect 25OHD3 levels measured. When blood volumes of <50 μL were spotted, 25OHD3 concentrations extracted were significantly lower (P  < 0.0001). We also observed a chromatographic effect across the surface of blood spots, with 25OHD3 concentrations significantly higher in outer punched spots compared to those punched from the centre (P  < 0.0001). This also correlates with a heavier net weight of blood from outer punched spots (P  < 0.0001). This effect was reproducible on two types of paper cards (Whatman 903® and FTA®), and paper type was shown to be highly relevant. We also show that the distribution of 25OHD3 in whole blood is essentially extracellular, with over 98% of 25OHD3 residing in the serum component. This may potentially explain why the diffusion properties of blood and type of chromatographic paper may significantly influence the distribution of such analytes in DBS. These factors should be taken into consideration for the prospective collection of DBS and analysis of 25OHD3 in DBS.
Keywords: Dried blood spots; 25-Hydroxyvitamin D; Punch location; Whatman 903; FTA; LC–MS/MS;

Rapid determination of human globin chains using reversed-phase high-performance liquid chromatography by Jun-Hui Wan; Pei-Ling Tian; Wei-Hao Luo; Bing-Yi Wu; Fu Xiong; Wan-Jun Zhou; Xiang-Cai Wei; Xiang-Min Xu (53-58).
► A simple and rapid RP-HPLC for human globin chains was established. ► RP-HPLC was useful for diagnosing β thalassemia and Hb H disease. ► A strategy for the separation of globins by RP-HPLC was discussed.Reversed-phase high-performance liquid chromatography (RP-HPLC) of human globin chains is an important tool for detecting thalassemias and hemoglobin variants. The challenges of this method that limit its clinical application are a long analytical time and complex sample preparation. The aim of this study was to establish a simple, rapid and high-resolution RP-HPLC method for the separation of globin chains in human blood. Red blood cells from newborns and adults were diluted in deionized water and injected directly onto a micro-jupiter C18 reversed-phase column (250 mm × 4.6 mm) with UV detection at 280 nm. Under the conditions of varying pH or the HPLC gradient, the globin chains (pre-β, β, δ, α, Gγ and Aγ) were denatured and separated from the heme groups in 12 min with a retention time coefficient of variation (CV) ranging from 0.11 to 1.29% and a peak area CV between 0.32% and 4.86%. Significant differences (P  < 0.05) among three groups (normal, Hb H and β thalassemia) were found in the area ratio of α/pre-β+β applying the rapid elution procedure, while P  ≥ 0.05 was obtained between the normal and α thalassemia silent/trait group. Based on the ANOVA results, receiver operating characteristic (ROC) curve analysis of the δ/β and α/pre-β+β area ratios showed a sensitivity of 100.0%, and a specificity of 100.0% for indicating β thalassemia carriers, and a sensitivity of 96.6% and a specificity of 89.6% for the prediction of hemoglobin H (Hb H) disease. The proposed cut-off was 0.026 of δ/β for β thalassemia carriers and 0.626 of α/pre-β+β for Hb H disease. In addition, abnormal hemoglobin hemoglobin E (Hb E) and Hb Westmead (Hb WS) were successfully identified using this RP-HPLC method. Our experience in developing this RP-HPLC method for the rapid separation of human globin chains could be of use for similar work.
Keywords: Reversed-phase high-performance liquid chromatography; Human globin chain; Thalassemia; Hemoglobin variant;

Instrumentation of hollow fiber flow field flow fractionation for selective cell elution by Tayssir Ibrahim; Serge Battu; Jeanne Cook-Moreau; Philippe Cardot (59-66).
► Mammalian nucleated cells are eluted in HF5 for the first time. ► In HF5 eluted cells fit with cell sorting requirements. ► Primary relaxation allows enhancing size dependent cell separations. ► Primary relaxation authorizes uploading of large ell suspension volume. ► The very low column volume, places HF5 in “micro scale” cell sorting domain.Hollow fiber flow field flow fractionation (HF5) columns can be built with minimized cost and instrumental skills by incorporation of commercial hollow fibers into holders made of classical chromatographic tubing and connectors. The proposed design leads to differential elution of human cells of different origin. Suspensions of red blood cells (RBC) and adherent human colorectal cancer (CRC) cell lines were used. These CRC nucleated population have been linked to cell-to-cell and cell to instrument interactions that are limiting factors in terms of recovery and viability. These interactions can be limited depending on injection/elution conditions. By using RBC we observed that the focalization/relaxation step played a major role in the elution process. However, HF5 opens a large potential, which completes the diversity shown by SdFFF in cell sorting methodologies and technologies.
Keywords: Hollow fiber flow field flow fractionation; Instrumentation; Focalization–relaxation; Cell sorting;

Determination of 6-keto prostaglandin F1α and its metabolites in human plasma by LC–MS/MS by Mark Enzler; Stefan Schipp; Laurent B. Nicolas; Jasper Dingemanse; Christoph Siethoff (67-71).
► A new HPLC–MS/MS method was developed and validated for the quantification. ► Improved selectivity in comparison to ligand-binding assays. ► First application to clinical trial samples obtained from a pharmacokinetic study.An HPLC–MS/MS method was developed and validated for the quantification of 6-keto prostaglandin F1α, the stable hydrolysis product of prostacyclin, and its metabolites 2,3-dinor-6-keto prostaglandin F1α and 6,15-diketo-13,14-dihydro prostaglandin F1α in human plasma. For sample preparation, a solid phase extraction step was combined with a column switching approach for analytes enrichment and further sample clean-up of the processed sample. The assay was validated in the concentration range 50.0–5000 pg/mL for 6-keto prostaglandin F1α and 6,15-diketo-13,14-dihydro prostaglandin F1α, and 100–10,000 pg/mL for 2,3-dinor-6-keto prostaglandin F1α. The inter-batch precision was better than 12.7%, 9.2%, and 9.4% for 6-keto prostaglandin F1α, 2,3-dinor-6-keto prostaglandin F1α, and 6,15-diketo-13,14-dihydro prostaglandin F1α, respectively. The inter-batch accuracy was between 97.3% and 100.8% for 6-keto prostaglandin F1α, between 97.5% and 103.0% for 2,3-dinor-6-keto prostaglandin F1α, and between 92.0% and 100.0% for 6,15-diketo-13,14-dihydro prostaglandin F1α. Further it has been demonstrated that the analytes were stable in plasma for 20 h at room temperature, during three freeze-and-thaw cycles, for 96 days at −25 °C storage temperature, and 50 h in the autosampler tray at room temperature.
Keywords: Prostaglandin F1α; 2,3-Dinor-6-keto prostaglandin F1α and 6,15-diketo-13,14-dihydro prostaglandin F1α; Quantification; Liquid chromatography; Mass spectrometry; Pharmacokinetic study;

Quantitative determination of zolmitriptan in rat blood and cerebrospinal fluid by reversed phase HPLC–ESI-MS/MS analysis: Application to in vivo preclinical pharmacokinetic study by Alessandro Dalpiaz; Nicola Marchetti; Alberto Cavazzini; Luisa Pasti; Sitaram Velaga; Elisabetta Gavini; Sarah Beggiato; Luca Ferraro (72-78).
► HPLC–ESI-MS/MS determination of zolmitriptan in rat blood and cerebrospinal fluid samples. ► Liquid–liquid extraction of zolmitriptan from 100 μL blood volume suitable for the pharmacokinetic study. ► Zolmitriptan in vivo pharmacokinetics after its intravenous and nasal administration in rat. ► HPLC–ESI-MS/MS method for the validation of novel zolmitriptan formulations.A fast HPLC–ESI-MS/MS method has been developed and validated for the quantification of the potent and selective antimigraine zolmitriptan in rat blood and cerebrospinal fluid (CSF). The assay has been then applied for in vivo preclinical studies. The analytical determination has been used to obtain pharmacokinetics of zolmitriptan in the two biological matrices after its intravenous or nasal administration. Liquid–liquid extraction of zolmitriptan was performed from 100 μL rat blood samples in the presence of N6-cyclopentyladenosine (internal standard) with the employment of ethyl acetate. Calibration standards were prepared by using blood matrix and following the same liquid–liquid extraction procedure. CSF samples were analyzed without any pre-treatment steps and by using an external calibration method in pure water matrix. Chromatographic separation was performed under reversed phase and a gradient elution condition on a C18 packed column (100 × 2.0 mm, 2.5 μm particles diameter). The mobile phase was a mixture between acetonitrile, water and formic acid (0.1% v/v). The applied HPLC–MS/MS method allowed low limits of detection, as calculated from calibration curves, of 6.6 and 24.4 ng/mL for water matrix and rat blood extracts, respectively. Linearity of the calibration curves was established up to 5 μM (1.44 μg/mL), as well as good assay accuracy. The intravenous infusion of 20 μg zolmitriptan to male Sprague-Dawley rats produced blood concentrations ranging from 9.4 ± 0.7 to 1.24 ± 0.07 μg/mL within 10 h, with a terminal half-life of 3.4 ± 0.2 h. The nasal administration of a water suspension of 20 μg zolmitriptan produced blood concentrations ranging from 2.92 ± 0.21 to 0.85 ± 0.07 μg/mL within 6 h. One hour after zolmitriptan intravenous infusion or nasal administration, its CSF concentrations were 0.0539 ± 0.0016 and 0.0453 ± 0.0012 μg/mL, respectively. This study determined the suitability of the herein proposed method to investigate the pharmacokinetics of zolmitriptan after its administration by means of novel formulations and, hence, to evaluate the efficacy of innovative nose-to-brain drug delivery in preclinical studies.
Keywords: Zolmitriptan; HPLC–ESI-MS/MS; Rat blood samples; Rat cerebrospinal fluid samples; Pharmacokinetics;

Impact of hemolysis during sample collection: How different is drug concentration in hemolyzed plasma from that of normal plasma? by Aimin Tan; Sébastien Gagné; Isabelle A. Lévesque; Sylvain Lachance; Nadine Boudreau; Ann Lévesque (79-84).
► Systematic evaluation of hemolysis impact on drug sequestration in plasma. ► Proposed a formula for estimating the impact for the first time. ► Hemolysis could impact the representability of hemolyzed plasma samples. ► The impact is compound-dependent. ► Evaluating hemolysis matrix effect only is not enough for hemolyzed plasma samples.Hemolysis is a common phenomenon in clinical studies. Despite the growing interest in hemolysis matrix effect, how hemolysis impacts the representability of hemolyzed plasma samples was rarely evaluated. The purpose of this research is to perform such an evaluation by theoretical consideration and experiment. A formula for estimating the impact is proposed, which includes the degree of hemolysis and the drug's red blood cell (RBC): plasma concentration ratio. The impact of hemolysis on the representability of hemolyzed plasma samples is compound-dependant. Given the same degree of hemolysis, the stronger a drug binds to RBCs, the more significant the impact of hemolysis. For a drug with high affinity to RBCs, the results of hemolyzed plasma samples may not be useful even though they are accurate. There is an overall agreement between theoretical predication and experimental results. Among the ten different drug compounds tested, only methazolamide, which binds strongly to RBCs, showed significant change in plasma concentration due to hemolysis.
Keywords: Hemolysis; Hemolyzed sample; Drug sequestration; Drug partition; Red blood cell; Methazolamide;

► Pazopanib (GW-786034) is an orally active tyrosine kinase inhibitor (TKI). ► Recently approved by USFDA for the treatment of advanced renal cell carcinoma. ► To examine the pre-clinical pharmacokinetics we developed an LC/MS–MS assay. ► To the best of our knowledge, no published report exists for pazopanib LCMS assay. ► We describe a simple extraction method, to quantify pazopanib for PK studies.A simple, rapid and sensitive liquid chromatography–tandem mass spectrometric (LC/MS–MS) method has been developed and validated for the quantitative determination of pazopanib in mouse plasma and brain tissue homogenate. Single liquid–liquid extraction step with ethyl acetate was employed for analysis of pazopanib and the internal standard (IS); vandetanib. HPLC separation was performed on an XTerra® MS C18 column 50 mm × 4.6 mm, 5.0 μm. The mobile phase consisted of 70% acetonitrile and 30% water with 0.1% formic acid, pumped at a flow rate of 0.25 ml/min. Analysis time was 3.5 min per run and both the analyte and IS eluted within 1.8–2.0 min. Multiple reactions monitoring (MRM) mode was utilized to detect the compounds of interest. The mass spectrometer was operated in the positive ion mode for detection. The precursor to product ions (Q1→Q3) selected for pazopanib and internal standard during quantitative optimization were (m/z) 438.1→357.2 and 475.0→112.2 respectively. The calibration curves were linear over the range of 3.9–1000 ng/ml in both biological matrices. Lower limit of quantification (LLOQ) for mouse plasma and brain tissue was 3.9 ng/ml. The values for inter and intra day precision and accuracy were well within the ranges acceptable for analytical assessment (<15%). This method was applied to determine brain to plasma concentration ratio and relevant pharmacokinetic parameters of pazopanib after a single intravenous dose of 5 mg/kg in FVB wild type mice.
Keywords: Mouse plasma; Pazopanib; GW-786034; Pharmacokinetics; LC/MS–MS; Brain tissue;

► BPAF is a concerned endocrine disrupting compound. ► A simple and universal analytical method was firstly developed for quantification of BPAF in bio-matrices. ► It was successfully applied to the determination of BPAF in tissues, serum, urine and feces of orally dosed rats.As a homologue of bisphenol A (BPA), there is concern about the potential reproductive and developmental toxicity of bisphenol AF (BPAF) based on in vitro tests. In this study, a simple and universal analytical method was developed for the determination of trace BPAF in various tissues and excreta of rats after they were orally dosed. The samples were hydrolyzed with glucuronidase/arylsulfatase followed by ultrasonic extraction with acetonitrile. The crude extract was purified with a mixed-mode anion exchange (Oasis MAX) solid-phase extraction (SPE) cartridge. Separation and quantification was then conducted by ultra-high-pressure liquid chromatography/electrospray ionization tandem mass spectrometry (LC–ESI-MS/MS) in negative ionization mode. The recoveries at three fortification levels in different biological samples were from 71.0% to 102.3% with relative standard deviations no more than 13.2% (n  = 6). The quantification limits of the method were from 0.5 μg/kg to 3 μg/kg depending on the matrix. This method was successfully applied to the determination of BPAF in tissues, serum, urine and feces of orally dosed rats.
Keywords: Bisphenol AF; Liquid chromatography–tandem mass spectrometry; Rat; Tissues; Excreta;

Matrix effect marker for multianalyte analysis by LC–MS/MS in biological samples by Eva Tudela; Gloria Muñoz; Jesús A. Muñoz-Guerra (98-106).
► The prevalence of acute matrix effect in the analysis of corticoids by LC–MS is studied. ► A novel and selective marker to identify cases with acute matrix effect is introduced. ► A non matrix affected LC–MS based method for the analysis of corticoids in doping control is proposed.Matrix effects (ion suppression/enhancement) are a well-observed phenomenon in analyses of biological matrices by high-performance liquid chromatography–mass spectrometry (LC–MS). However, few simple solutions for detecting and minimizing these adverse effects have been described so far in multianalyte analysis, especially in the field of doping control.This study describes an exhaustive characterization of matrix effects in one hundred urine samples fortified with 41 analytes (glucocorticoids and diuretics). It introduces a novel marker to identify samples in which the reliability of the results is compromised because of acute ion suppression. This new strategy strengthens the rigor of the analysis for screening purposes. Once the matrix effect is identified, a selective sample preparation is introduced to minimize the adverse ion suppression effect. That selective extraction together with the use of a deuterated internal standard permits enhancing the ruggedness of the estimation of glucocorticoid concentration in urine.
Keywords: Doping control; Ion suppression; Liquid chromatography–mass spectrometry; Urine; Glucocorticoids; Diuretics;

► Truly one-point calibration (y  =  C, where C is constant) proposed. ► Its pros, cons and applicability discussed. ► Utility in fields where regulatory compliance requires measurand to be within limits. ► Simple fit-to-purpose Yes/No method for pesticide residue control in food developed.This paper presents the development of a simple fit-for-purpose Yes/No method for controlling pesticide residues in food by liquid chromatography tandem mass spectrometry (LC–MS/MS). A true one-point calibration (y  =  C, where C is a constant) was evaluated for its applicability, feasibility and performance in controlling pesticides in fruits. A process analytical technology approach was adopted. One-point calibrations equivalent to the maximum residual level (MRL) of a pesticide in a fruit were performed and used as the process and quality control parameters. The confidence level intervals were determined and used for controlling the pesticide residue levels in real fruit samples. Useful features of the proposed method, from practical point of view, include the easy access to historical data, their simple presentation, the simplicity of introducing new measurement data points, and these features make it an excellent diagnostic and analytical tool. This technique allows any method performance abnormality to be flagged early and reliable information on exceeding MRLs to be obtained quickly. This truly one-point calibration may find applications in any field where regulatory compliance requires that a measurand is shown to be within a particular limit.
Keywords: Truly one-point calibration; Truly single-point calibration; Pesticide residue; Liquid chromatography–mass spectrometry (LC–MS); Analytical method;

► Four extractions were compared for the quantification of sinigrin from mustard. ► Isothiocyanates were also extracted from each sinigrin extract. ► 50% acetonitrile was the most efficacious extraction solvent for sinigrin. ► Freeze-drying prior to analysis had a negative impact on isothiocyanate content. ► Extraction of both sinigrin and isothiocyanates was possible using boiling water.Glucosinolates are β-thioglycosides which are found naturally in Cruciferae including the genus Brassica. When enzymatically hydrolysed, glucosinolates yield isothiocyanates and give a pungent taste. Both glucosinolates and isothiocyanates have been linked with anticancer activity as well as antifungal and antibacterial properties and therefore the quantification of these compounds is scientifically important. A wide range of literature exists on glucosinolates, however the extraction and quantification procedures differ greatly resulting in discrepancies between studies. The aim of this study was therefore to compare the most popular extraction procedures to identify the most efficacious method and whether each extraction can also be used for the quantification of total isothiocyanates. Four extraction techniques were compared for the quantification of sinigrin from mustard cv. Centennial (Brassica juncea L.) seed; boiling water, boiling 50% (v/v) aqueous acetonitrile, boiling 100% methanol and 70% (v/v) aqueous methanol at 70 °C. Prior to injection into the HPLC, the extractions which involved solvents (acetonitrile or methanol) were freeze-dried and resuspended in water. To identify whether the same extract could be used to measure total isothiocyanates, a dichloromethane extraction was carried out on the sinigrin extracts. For the quantification of sinigrin alone, boiling 50% (v/v) acetonitrile was found to be the most efficacious extraction solvent of the four tested yielding 15% more sinigrin than the water extraction. However, the removal of the acetonitrile by freeze-drying had a negative impact on the isothiocyanate content. Quantification of both sinigrin and total isothiocyanates was possible when the sinigrin was extracted using boiling water. Two columns were compared for the quantification of sinigrin revealing the Zorbax Eclipse to be the best column using this particular method.
Keywords: Allyl isothiocyanate; Brassica juncea; Column; Glucosinolate; Theoretical plate;

► The analytes of interest were well separated. ► The method is simple, good specificity, robust and time efficient. ► Successfully applied to pharmacokinetic study in healthy volunteers.A simple, sensitive and high-throughput ultra high-performance liquid chromatography electrospray ionization mass spectrometry (U-HPLC–ESI-MS/MS) method has been developed and validated for the determination of ranolazine in human plasma. Propafenone was employed as the internal standard (I.S.). The analytes were chromatographically separated on a BEH C18 column (50 mm × 2.1 mm, 1.7 μm) with a mobile phase consisting of acetonitrile and aqueous ammonium acetate solution (0.06% formic acid, 7.5 mmol L−1 ammonium acetate, 40:60, v/v). Detection of the analytes was achieved using positive ion electrospray ionization via multiple reactions monitoring mode. The mass transitions were m/z 428.3 → 279.3 for ranolazine and m/z 342.4 → 115.9 for propafenone. The assay was linear over the concentration range 1–3000 ng mL−1, with correlation coefficients ≥0.997. The intra- and inter-day coefficients of variation were less than 8.9% in terms of relative standard deviation and accuracy ranged from 93.0 to 108.9% at all quality control levels. The validated method was a simple sample preparation procedure and short run-time (<2.0 min) method, which was successfully applied to a phase I pharmacokinetic study of ranolazine in Chinese healthy volunteers.
Keywords: Ranolazine; U-HPLC–ESI-MS/MS; Human plasma; Pharmacokinetics;