Determination of cholesterol in human hair using gas chromatography-mass spectrometry

This work describes a sensitive method for determining cholesterol in human hair using GC-MS. In this study, we used a very small amount of hair, only 1 mg, to quantify cholesterol. We also can achieve more effective purification and a good recovery over 92% with solid-phase extraction using an Oasis HLB cartridge. The intra-day and inter-day precision and accuracy values were less than 7.08%. Cholesterol was determined to be in the range of 355-1693 microg/g in healthy human hair. We tested the concentration correlation between the serum and hair to examine the feasibility of using the hair cholesterol level as an index of the serum cholesterol level. The correlation between the serum cholesterol was 0.86 (r-value) in patients with hypercholesterolemia. This finding indicates that, in the clinical field, hair could replace serum in cholesterol level measurement.     

Development and validation of a liquid chromatography and ion spray tandem mass spectrometry method for the quantification of artesunate, artemether and their major metabolites dihydroartemisinin and dihydroartemisinin-glucuronide in sheep plasma

Recently, promising fasciocidal activities of artesunate and artemether were described in rats and sheep. Therefore, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to quantify artesunate, artemether and their metabolites dihydroartemisinin and dihydroartemisinin-glucuronide in sheep plasma. Protein precipitation with methanol was used for sample workup. Reversed-phase high-performance liquid chromatography (HPLC) was performed using an Atlantis C18 analytical column with a mobile phase gradient system of ammonium formate and acetonitrile. The analytes were detected by MS/MS using selected reaction monitoring (SRM) with electrospray ionisation in the positive mode (transition m/z 267.4 → 163.0). The analytical range for dihydroartemisinin, dihydroartemisinin-glucuronide and artesunate was 10-1000 ng/ml and for artemether 90-3000 ng/ml with a lower limit of quantification of 10 and 90 ng/ml, respectively. Inter- and intra-day accuracy and precision deviations were < 10%. Consistent relative recoveries (60-80%) were observed over the investigated calibration range for all analytes. All analytes were stable in the autosampler for at least 30 h (6 °C) and after three freeze and thaw cycles. The validation results demonstrated that the LC-MS/MS method is precise, accurate and selective and can be used for the determination of the artemisinins in sheep plasma. The method was applied successfully to determine the pharmacokinetic parameters of artesunate and its metabolites in plasma of intramuscularly treated sheep.     

LC-ESI-MS/MS method for quantification of ambrisentan in plasma and application to rat pharmacokinetic study

A sensitive high‐performance liquid chromatography–positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of ambrisentan in plasma. The analyte and the internal standard (armodafinil) were extracted from plasma by acetonitrile precipitation and they were separated on a reversed‐phase C₁₈ column with a gradient program. The MS acquisition was performed with multiple reaction monitoring mode using the respective [M + H]⁺ ions, m/z 379–347 for ambrisentan and m/z 274–167 for the IS. The assay exhibited a linear dynamic range of 1–2000 ng/mL for ambrisentan in plasma. Acceptable precision (<10%) and accuracy (100 ± 8%) were obtained for concentrations over the standard curve range. The method was successfully applied to quantify ambrisentan concentrations in a rodent pharmacokinetic study after a single oral administration of ambrisentan at 2.5 mg/kg to rats. Following oral administration the maximum mean concentration in plasma (C_max; 1197 ± 179 ng/mL) was achieved at 1.0 ± 0.9 h (T_max), and the area under the curve (AUC) was 6013 ± 997 ng h/mL. Therefore, development of such a simple and sensitive method in rat plasma should translate into a method for ambrisentan in human plasma for clinical trials. Copyright © 2012 John Wiley & Sons, Ltd.     

Development and validation of a hydrophilic interaction chromatography–tandem mass spectrometry for quantification of nicotine and its metabolites in human maternal and cord sera

A selective and sensitive HILIC‐MS/MS method for the simultaneous quantification of nicotine and its metabolites in human maternal and cord sera was developed and validated. After solid‐phase extraction, LC separation was achieved on a hydrophilic interaction chromatography. The validated method is capable of selective identification as well as accurate and sensitive quantification. Analyte recovery ranged from 86.2 to 107.7% and intra‐ and inter‐day assay precision were less than 15% relative standard deviation. This sensitive HILIC‐MS/MS method can be used to determine nicotine and its metabolic profile in smokers. This validated method is useful for the determination of nicotine and its metabolites in human serum in future studies of the effects of nicotine exposure on neonatal outcome. Copyright © 2010 John Wiley & Sons, Ltd.     

同时测定室内吸烟环境空气中尼古丁和3-乙烯基吡啶的方法

以XAD-4树脂为吸附剂，含三乙胺0．0l％的乙酸乙酯为溶剂，GC／MS为检测手段，以及内标校正曲线定量，建立一套可以同时测定吸烟环境室内空气中尼古丁和3-乙烯基吡啶标志物含量的分析方法。尼古丁的检出限和平均脱附率分别为0．075μg/样品和91．80％；3-乙烯基吡啶分别为0．089μg/样品和95．90％。通过实际样品的测定，讨论了该方法的应用效果。     

Determination of cocaine and cocaethylene in urine by solid-phase microextraction and gas chromatography-mass spectrometry

In order to evaluate recent cocaine exposure or its coingestion with ethanol, a simple and sensitive solid-phase microextraction (SPME) procedure for determination of cocaine and cocaethylene in urine was developed and validated. A polydimethylsiloxane fibre (100 microm) was submersed in the urine sample for 20 min under magnetic stirring after alkalinization with solid buffer (NaHCO(3):K(2)CO(3), 2:1). Gas chromatography-mass spectrometry (GC-MS) was used to identify and quantify the analytes in selected ion monitoring mode (SIM). The limits of quantification were 5.0 ng/mL for both analytes. Good inter- and intra-assay precision was also observed (coefficient of variation <9%).     

Simultaneous determination of honokiol and magnolol in Magnolia officinalis by liquid chromatography with tandem mass spectrometric detection

An optimized high-performance liquid chromatographic method coupled with tandem mass spectrometric detection (LC-MS/MS) was developed for the simultaneous determination of honokiol and magnolol in Magnolia officinalis. Honokiol and magnolol were separated from the extracts using a reversed-phase C(18) column with a mobile phase consisted of acetonitrile and water (75:25, v/v) at a flow-rate of 0.8 mL/min. Selected reaction monitoring (SRM) mode was used for all sample quantification by the precursor-ion/product ion pair m/z 265 --> m/z 224 for honokiol and m/z 265 --> m/z 247 for magnolol. Validation data showed that this method has good linearity (r(2) > 0.995) over the concentration range of 0.0025-0.5 microg/mL for honokiol and magnolol, and both intra- and inter-day variability were acceptable within 15% at the lowest concentrations for this method. This proposed method provides excellent specificity, higher sensitivity and shorter run time than conventional methods and was applied successfully to determine the contents of honokiol and magnolol in M. officinalis.     

头发中内源性类固醇激素的气相色谱-串联质谱分析

建立了建康人头发中内源性类固醇兴奋剂睾酮、表睾酮、雄酮、苯胆烷醇酮和脱氢表雄酮的气相色谱-串联质谱(GC-MS/MS)分析方法。头发经碱水解后,以乙醚提取,经衍生化后采用GC-MS/MS的多反应监测模式(MRM)分析。方法的线性关系良好,检出限达0.1～0.2 pg/mg;提取回收率为74.6%～104.5%;日内测定的准确度为90.1%～113.7%,日内及日间测定的精密度均小于17.5%。应用所建立的方法测定了80例中国健康人头发中睾酮、表睾酮、雄酮、苯胆烷醇酮和脱氢表雄酮的生理水平,为内源性类固醇兴奋剂滥用的判断提供了方法和基础数据。     

Sensitive liquid chromatography tandem mass spectrometry method for the quantification of Quetiapine in plasma

A sensitive high-performance liquid chromatography-tandem mass spectrometry method was developed and validated for the quantification of quetiapine in rat plasma. Following liquid-liquid extraction, the analyte was separated using a gradient mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H]+ ions, m/z 384 to m/z 221 for quetiapine and m/z 327 to m/z 270 for the internal standard. The assay exhibited a linear dynamic range of 0.25-500 ng/mL for quetiapine in rat plasma. The lower limit of quantification was 0.25 ng/mL with a relative standard deviation of less than 7%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The validated method was successfully used to analyze rat plasma samples for application in pre-clinical pharmacokinetic studies. This method in rodent plasma could be adapted for quetiapine assay in human plasma.     

Development and validation of a liquid chromatography-tandem mass spectrometry method to determine ulifloxacin, the active metabolite of prulifloxacin in rat and rabbit plasma: application to toxicokinetic study

A simple, high‐throughput and specific high‐performance liquid chromatography–tandem mass spectrometry method has been developed and validated according to the FDA guidelines for quantification of ulifloxacin in rat and rabbit plasma. The analyte was separated on a Peerless basic C₁₈ column (33 × 4.6 mm, 3 µm) with an isocratic mobile phase of methanol–water containing formic acid (0.5%, v/v; 9:1, v/v) at a flow rate of 0.5 mL/min. The MS/MS detection was carried out by monitoring the fragmentation of m/z 350.500 → 248.500 for ulifloxacin and m/z 332.400 → 231.400 for ciprofloxacin (internal standard; IS) on a triple quadrupole mass spectrometer. The response to ulifloxacin was linear over the range 0.010–2.500 µg/mL in both plasma. The limit of detection and lower limit of quantification of ulifloxacin were determined in both species to be 0.0025 and 0.010 µg/mL, respectively. The method was successfully applied to quantitatively assess the toxicokinetics of ulifloxacin in rat and rabbit following a single 400 mg/kg (in rat) and 200 mg/kg (in rabbit) oral dose of the prulifloxacin. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of tebuconazole, trifloxystrobin and its metabolite in fruit and vegetables by a Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method using gas chromatography with a nitrogen-phosphorus detector and ion trap mass spectrometry

A new analytical method using QuEChERS procedure by gas chromatography with a nitrogen-phosphorus detector (GC-NPD) and ion trap mass spectrometry (GC-IT-MS) for the quantitative determination of tebuconazole, trifloxystrobin and its metabolite trifloxystrobin acid has been developed and validated. The analytes were extracted from five fruit and vegetable matrices using acetonitrile and subsequently cleaned up using primary secondary amine (PSA) or octadecylsilane (C18) as sorbent prior to GC analysis. The present methods provided sufficient sensitivity as reflected by the values of limit of detection (LOD) and limit of quantification (LOQ) of 0.4-7 and 1.2-20 μg/kg for GC-IT-MS/MS and GC-NPD. The recoveries were, on average, 68-117 and 68-121%, respectively, for three compounds by GC-NPD and GC-IT-MS/MS with intra-day precision achieved with an RSD of 2.7-19.1%. The inter-day precision was better than 15.1% as determined by GC-NPD. The QuEChERS procedure, by using two sorbents (PSA and C18) and the matrix-matched standards, gave satisfactory recoveries and RSD values in different matrices. IT-MS acquisition provided higher specificity and selectivity for pesticides and better limit of detection and quantification. However, the repeatability and precision of NPD method were better compared with IT-MS.     

Liquid chromatography-mass spectrometry method for the determination of venlafaxine in human plasma and application to a pharmacokinetic study

A sensitive and selective liquid chromatographic-mass spectrometric (LC-MS) method for the determination of venlafaxine in human plasma has been developed. Samples were prepared using liquid-liquid extraction and analyzed on a C(18) column interfaced with a triple quadrupole mass spectrometer. Positive electrospray ionization was employed as the ionization source. The mobile phase was methanol-water containing 10 mmol/L ammonium acetate, pH 7.9 adjusted with aqueous ammonia (80:20, v/v) at the flow rate of 1.0 mL/min. The analyte and internal standard clozapine were both detected by use of selected ion monitoring mode. The method was linear in the concentration range of 1.0-200.0 ng/mL. The lower limit of quantification (LLOQ) was 1.0 ng/mL. The intra- and inter-day relative standard deviation across three validation runs over the entire concentration range was less than 10.1%. The accuracy determined at three concentrations (5.0, 50.0 and 150.0 ng/mL for venlafaxine) was within +/-10.0% in terms of relative error (RE). The method was successfully applied for the evaluation of pharmacokinetic profiles of venlafaxine capsule in 20 healthy volunteers. The results show AUC, T(max), C(max) and T(1/2) between the testing formulation and reference formulation have no significant difference (p > 0.05). Relative bioavailability was 103.4 +/- 14.1%.     

Optimisation of a solid-phase microextraction method for the analysis of nicotine in hair

A headspace solid-phase microextraction method (HS-SPME) followed by gas chromatography with mass spectrometric detection (GC/MS) has been developed for the determination of low concentrations of nicotine in hair. Parameters affecting the SPME procedure including type of fiber coating, extraction mode, extraction temperature and time, desorption time, stirring, and salt addition have been evaluated and optimised. The method provided good linearity (r(2)≥0.9980) over the concentration range tested (0.2-20 ng/mg) and low detection limit (0.02 ng/mg). Precision expressed as relative standard deviation was <10%. The average accuracy was 95%. The proposed method was used to determine hair nicotine levels in 100 children in order to assess exposure to environmental tobacco smoke (ETS). The described HS-SPME procedure is fast, simple, sensitive, and solvent-free and is therefore suitable for studies involving ETS exposure assessment.     

Comparison of enzyme-linked immunosorbent assay with liquid chromatography-tandem mass spectrometry for the determination of diethylstilbesterol residues in chicken and liver tissues

A competitive enzyme-linked immunosorbent assay (ELISA) was developed for the quantitative detection of the diethylstilbesterol (DES). Polyclonal rabbit antisera, raised against protein conjugate diethylstilbesterol-mono-caroxyl-propyl-ethyl-bovine-serum-albumin (DES-MCPE-BSA), were utilized in immobilized antibody-based and competitive immunoassays. Assay conditions, including concentrations of antisera and horseradish peroxidase, (HRP)-DES, were optimized. The effects of incubation time, surfactant concentration, ionic strength and pH of the medium were also investigated. The typical calibration curve gave an average IC(50) value of 2.4 ng/mL, calibration range from 0.2 to 30.5 ng/mL and a detection limit of 0.07 ng/mL. The specificity of the assay was tested against DES structurally related compounds, and the assay proved highly selective for DES. Assay performance was validated using spiked chicken meat and liver tissue samples. Moreover, it was compared with liquid chromatography-tandem mass spectrometry. The ion pair for quantification of DES was m/z 267.4/251.4, and the linear equation of DES was y = 0.1033x + 0.0126 (r = 0.9960). The two analytical methods can be applied to monitor DES and other steroid residues in foods.     

Methods for the characterization of Jet Propellent-8: vapor and aerosol

Jet Propellant‐8 (JP‐8) has been responsible for the majority of reported chemical exposures by the US Department of Defense. Concerns related to human exposure to JP‐8 are relatively new; therefore, there is a lack of literature data. Additionally, health effects related to the composition of the exposure have only recently been considered. Two major questions exist: (1) what is the compositional difference between the aerosol and vapor portions of JP‐8 under controlled conditions and (2) what is the most representative method to sample JP‐8 aerosol and vapor? Thirty‐seven standards, representing more than 40% of the mass of JP‐8, were used for characterization of the neat fuel, vapor and aerosol portions. JP‐8 vapor samples at a concentration of 1600 mg/m³ were prepared in Tedlar bags. A portion of the vapor samples was adsorbed on charcoal, Tenax and custom mixed phase sorbents. These samples were then extracted using organic solvent and analyzed using gas chromatography/mass spectrometry. The vapor samples extracted from the sorbent tubes were directly compared with a vapor bag. The samples collected using Tenax sorbent tubes were found to be most representative of the composition of the vapor bags. In another set of experiments, aerosolized JP‐8 was generated using a collision nebulizer. Aerosol samples were collected and the chemical composition was characterized. The entire aerosol distribution was collected on a glass filter, extracted into solvent, and analyzed by GC‐MS. Finally, the composition of the vapor and aerosol was compared. The vapor was found to represent the lower molecular weight components of JP‐8, while the aerosol was composed of higher molecular weight components. Therefore, the vapor and aerosol should be treated as two discrete forms of exposure to JP‐8. Copyright © 2007 John Wiley & Sons, Ltd.     

Development and validation of automated SPE-HPLC-MS/MS methods for the quantification of asenapine, a new antipsychotic agent, and its two major metabolites in human urine

To support the evaluation of the pharmacokinetic parameters of asenapine (ASE) in urine, we developed and validated online solid‐phase extraction high‐performance liquid chromatography methods with tandem mass spectrometry detection (SPE‐LC‐MS/MS) for the quantification of ASE and two of its major metabolites, N‐desmethylasenapine (DMA) and asenapine‐N⁺‐glucuronide (ASG). The linearity in human urine was found acceptable for quantification in a concentration range of 0.500–100 ng/mL for ASE and DMA and 10.0–3000 ng/mL for ASG, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of apomorphine in canine plasma by liquid chromatography-electrospray ionization mass spectrometry and its application to a pharmacokinetic study

An LC-ESI-MS method was developed and validated for the assay of apomorphine in canine plasma using one-step liquid-liquid extraction. The analytes were separated on a Phenomenex Gemini C18 (150 mm x 2.0 mm id 3 microm) column and determined by MS in the positive ion mode. The linear range was 0.4-40 ng/mL with an LOD of 0.2 ng/mL for apomorphine in plasma. The intraday and interday precision and accuracy of quality control samples were < 5.9% RSD and < 7.5% bias for apomorphine. Extraction recoveries were > 80%. The validated method was successfully applied to analyze canine plasma samples in a pharmacokinetic study of apomorphine in dogs and detailed pharmacokinetic parameters were calculated.     

Identification of volatile components in Angelica species using supercritical-CO2 fluid extraction and solid phase microextraction coupled to gas chromatography-mass spectrometry

As a part of our search for environmentally friendly solvents to extract the active components of medicinal plants, two sampling techniques, supercritical fluid extraction (SFE) using CO(2) and solid-phase microextraction (SPME) were compared for their efficacy in the analysis of volatiles rhizome components emitted from the medicinal herbs Angelica gigas NAKAI (Korean danggui), Angelica sinensis (Chinese danggui), and Angelica acutiloba (Japanese danggui). A total of 54 compounds released from all of these varieties of Angelica rhizomes were separated and identified by gas chromatography-mass spectrometry (GC-MS). The composition of supercritical extracts from these plants was very different from the solid-phase microextraction products. More compounds were detected by SPME-GC-MS (41) than by SFE-GC-MS (17). The results of these analyses suggest that SFE may be useful for detecting the main components, decursinol angelate and decursin in Korean danggui, and butylidene dihydro-phthalide in both Chinese and Japanese danggui, whereas the results for SPME did not. The SFE method required specialized instrumentation, required little time to prepare the sample, and had a small sample size and no organic solvent. In sum, these results suggest that SFE is useful for extracting the volatile main components of danggui cultivars. Its simplicity, low cost and speed may allow SPME to increase the recovery of volatile components in general without disturbing the main components of the plant.     

Rapid and simple liquid chromatography tandem mass spectrometry method for the quantification of zidovudine in rat plasma

A high-performance liquid chromatography/electrospray ionization tandem mass spectrometry method was developed and validated for the quantification of zidovudine in rat plasma. Following solid-phase extraction, the analytes were separated using an isocratic mobile phase on a reverse phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 268/127 for zidovudine and m/z 230/112 for the internal standard. The method exhibited a linear dynamic range of 5-500 ng/mL for zidovudine in rat plasma. The lower limit of quantification was 5 ng/mL with a relative standard deviation of less than 8%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 1.5 min for each sample made it possible to analyze more than 400 plasma samples per day. The validated method was applied for pharmacokinetic studies of the novel drug delivery systems of zidovudine in rats.     

Liquid chromatography tandem mass spectrometry method for the quantification of clonidine with LLOQ of 10 pg/mL in human plasma

A sensitive high-performance liquid chromatography-positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of clonidine in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H](+) ions, m/z 230 to 44 for clonidine and m/z 254 to 44 for the internal standard. The assay exhibited a linear dynamic range of 10-2000 pg/mL for clonidine in human plasma. The lower limit of quantification was 10 pg/mL with a relative standard deviation of less than 6.8%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.5 min for each sample made it possible to analyze more than 250 human plasma samples per day. The validated method was successfully used to analyze human plasma samples for application in pharmacokinetic studies. Copyright (c) 2008 John Wiley & Sons, Ltd.