Electrospray Ionization-tandem Mass Spectrometry Method Research Articles

Direct multiclass desorption electrospray ionization-tandem mass spectrometry method for the analysis of sleep inducers and ototoxic drugs in dried blood spots.

An unconventional and innovative approach for the quantitative determination of 11 ototoxic and narcoleptic drugs in whole blood is described. The multiclass method allows the inclusion of the most widespread drugs on the market (antihistamines, antidepressants, antihypertensives, anxiolytics, opioids, Z-drugs) responsible for 10% of occupational accidents. The developed procedure involved the use of the desorption electrospray ionization (DESI) interface for the direct analysis of dried blood spots (DBS). All the issues strictly connected to the chemical-physical characteristics of DBS and DESI (sample inhomogeneity, DBS support, DESI geometry and solvent) were carefully evaluated and innovative strategies were applied. Haematocrit was managed using a small and measured volume of blood (2μL) with analysis of the entire DBS. The proposed method was fully validated in terms of limits of detection, limits of quantitation (LOQs; between 60 pg/mm2 and 1.6ng/mm2 ), linearity (one order of magnitude starting from LOQs) and inter- and intra-day precision (on three levels, with relative standard deviation values not exceeding 17%). Accuracy was calculated by comparison with an ultrahigh-performance liquid chromatography-tandem mass spectrometry method (suitable also as a confirmatory method). Results showed a surprising sensitivity, demonstrating that this procedure could be suitable for applications in various fields, e.g. forensic analysis. Moreover, as a collateral benefit, it was discovered that the method is able to analyse very light traces left on plastic and glass surfaces by detached dried blood.

Determination of Endocrine Disrupting Chemicals in Water and Wastewater Samples by Liquid Chromatography-Negative Ion Electrospray Ionization-Tandem Mass Spectrometry.

A liquid chromatography-negative ion electrospray ionization-tandem mass spectrometry method was developed for the simultaneous analysis of bisphenol A, 4-octylphenol, 4-nonylphenol, diethylstilbestrol, 17β-estradiol, estriol, estrone, 17α-ethinylestradiol, prednisone, and prednisolone. This method used solid-phase extraction with an elution solvent of acetonitrile to improve the stability of the analytes. To maintain the stability of analytes analyses were completed within five days. The recoveries ranged from 84 to 112% and the relative standard deviation of analysis of duplicate samples was <10%. The limits of quantitation were 1–10 ng/L. Surface water and wastewater were obtained from five wastewater treatment plants in Saskatchewan. Matrix effects were moderate to severe. Using standard addition calibration, all analytes except diethylstilbestrol and 17α-ethinyl estradiol were detected. There was a low frequency of detection of the target analytes in upstream and downstream water, indicating good removal efficiency during the wastewater treatment process. Bisphenol A and 4-nonylphenol were the only analytes detected downstream. Bisphenol A was the most frequently detected in raw wastewater (133 to 403 ng/L). Estriol was detected more often in raw wastewater than estrone or 17β-estradiol. This is the first Canadian study with the detection of prednisone and prednisolone with concentrations at 198–350 ng/L in raw wastewater at 60% of the wastewater treatment plants.

Quantification of lamotrigine in patient plasma using a fast liquid chromatography-tandem mass spectrometry method with backflush technology.

Recent concerns have been raised by neurologists and patients with epilepsy regarding the bioequivalence of generic lamotrigine to the brand Lamictal. Bioequivalence studies require the quantification of lamotrigine in human plasma, including in the presence of other drugs, for studies that will use patients with epilepsy rather than healthy volunteers. Lamotrigine was extracted from plasma through a simple protein precipitation and analyzed by fast liquid chromatography coupled to heated electrospray ionization with tandem mass spectrometric detection. A backflush step to remove interferent accumulation on column was included, and a stable isotope-labeled lamotrigine was used as an internal standard. The method was validated for accuracy, precision, interday and intraday coefficient of variation, specificity, lower limit of detection, lower limit of quantification, linearity, range, instrument precision, freeze-thaw, dilution integrity, and sample stability. Specificity evaluation included consideration of the impact of other antiepileptic drugs. The described method has a linear range of 8-10,000 ng/mL of lamotrigine (r = 0.9999) and a lower limit of detection of 1 ng/mL and a lower limit of quantification of 8 ng/mL. Intraday and interday reproducibility were less than 10.0% relative SD and 10.4% relative SD, respectively, and the percent recovery varied from 96.6% to 109.3% at various lamotrigine concentrations. A backflush step reduced matrix effects and no interference peak from plasma or other antiepileptic drugs were observed. A liquid chromatography-heated electrospray ionization-tandem mass spectrometry method including a backflush step was developed and validated to measure lamotrigine concentration in patient plasma. The method will be applied to bioequivalence studies that compare brand versus generic lamotrigine.

Quantification of ketamine and norketamine in bovine plasma by liquid chromatography–tandem mass spectrometry

The aim of present study was to develop a rapid and reliable analytical method for quantification of ketamine and its major metabolite, norketamine, in bovine plasma. A cost-effective and high-throughput extraction procedure was combined with a sensitive and specific liquid chromatography–heated electrospray ionization-tandem mass spectrometry method. Sample preparation consisted of a protein precipitation step using methanol followed by a clean-up using a HybridSPE®-phospholipid column and further dilution by a factor 1/10 with water before injection onto the LC–MS/MS instrument. A gradient elution program was performed with 1 % formic acid in water and 0.1 % acetic acid in methanol as mobile phases. Ionization was performed by a heated electrospray ionization (h-ESI) probe operating in the positive ionization mode. Following transitions were monitored in the selected reaction monitoring mode: 238.0 > 124.9/220.0 for ketamine and 224.0 > 207.0/124.9 for norketamine. The method was validated in-house. Matrix-matched calibration graphs were prepared for ketamine and norketamine and correlation and goodness-of-fit coefficients were 0.9991 and 0.9997 and 7.7 and 4.0 %, respectively. The within- and between-run precision and accuracy were evaluated and the results fell within the ranges specified. The limit of quantification was 0.1 µg/mL for both analytes, whereas limits of detection were 9.6 and 3.5 ng/mL for ketamine and norketamine, respectively. The method was applied on biological samples from a pharmacokinetic study in calves and demonstrated the suitability of the method for this application.

Determination of Niclosamide in Aquatic Animal Tissue by a Novel Extraction Procedure and High-Performance Liquid Chromatography–Heated Electrospray Ionization-Tandem Mass Spectrometry

Niclosamide is a mollusicide used for aquaculture on a large scale in China. However, it has high toxicity to aquatic animals and may cause damage to DNA. A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction procedure with high-performance liquid chromatography–heated electrospray ionization-tandem mass spectrometry method was developed for its determination. Samples were extracted with ammoniated acetonitrile, and anhydrous magnesium sulfate was added to remove moisture and precipitate proteins. The extracts were further purified with octadecylsilane. The recoveries of niclosamide in fortified muscle tissue at concentrations of 0.5 to 20 µg/kg were between 76.40% and 95.60% with relative standard deviations less than 9.54%. The limits of detection and quantification were 0.2 µg/kg and 0.5 µg/kg, respectively. The developed method was used to study the adsorption of niclosamide in channel catfish after administration.

Development and validation of liquid chromatography–tandem mass spectrometry method for simultaneous determination of six steroidal saponins in rat plasma and its application to a pharmacokinetics study

A specific and reliable liquid chromatography–electrospray ionization-tandem mass spectrometry method was developed for the simultaneous determination of timosaponin H1 (TH1), timosaponin E1 (TE1), timosaponin E (TE), timosaponin B-II (TB-II), timosaponin B-III (TB-III) and anemarrhenasaponin I (AS-I) in rat plasma. After addition of internal standard (IS) ginsenoside Rh1, plasma samples were pretreated by protein precipitation with acetonitrile. Chromatographic separation was performed on a reverse phase ACQUITY™ BEH C18 column (100mm×2.1mm i.d., 1.7μm) using a gradient mobile phase system of acetonitrile–water containing 0.05% formic acid and 5mM ammonium formate. The triple quadruple mass spectrometer was set in negative electrospray ionization mode and multiple reaction monitoring (MRM) was used for six steroidal saponins quantification. The precursors to produce ion transitions monitored for TH1, TE1, TE, TB-II, TB-III, AS-I and IS were m/z 1211.5>1079.6, 935.5>773.4, 935.4>773.5, 919.6>757.4, 901.5>739.3, 757.4>595.3 and 637.3>475.3, respectively. The method validation was conducted over the curve range of 0.5–400ng/mL for the six saponins. The intra- and inter-day precisions (RSD%) were less than 9.4% and the average extraction recoveries ranged from 82.5% to 97.8% for each analyte. Six steroidal saponins were proved to be stable during sample storage, preparation and analytical procedures. The validated method was successfully applied for the first time to determine the concentrations of six main steroidal saponins in incurred rat plasma samples, after intragastric administration of the extract of Anemarrhena asphodeloides Bge. for a rat pharmacokinetic study.

Simultaneous determination of glimepiride and pioglitazone in human plasma by liquid chromatography-tandem mass spectrometry and its application to pharmacokinetic study.

The rapid, sensitive, and selective liquid chromatography-electrospray ionization-tandem mass spectrometry method (LC-ESI-MS/MS) for the simultaneous estimation and pharmacokinetic investigation of glimepiride and pioglitazone in human plasma has been developed and fully validated. Glimepiride and pioglitazone, compounds which exert synergistic effects on blood glucose control, were investigated in human plasma using deuterium-labeled analogs as internal standards (IS). Liquid-liquid extraction was carried out on 0.2 mL of human plasma using ethyl acetate, and chromatographic separation was performed on an Agilent Eclipse plus C18 column (4.6 mm × 100 mm, 3.5 μm) using a mobile phase consisting of methanol-water-formic acid (95:5:0.1, v/v/v, plus 5mM ammonium acetate) at a flow rate of 0.8 mL/min. To quantify glimepiride, pioglitazone and their IS, multiple reaction monitoring (MRM) transitions of m/z 491.2→352.2, m/z 496.2→357.2, m/z 357.2→134.2 and m/z 361.2→138.2 were performed in positive mode. The total run time was 3.0 min and the elution time was about 2.4 min. The method exhibited good separation of analytes, without interference from endogenous substances. The linear calibration curves were 0.2-250 ng/mL for glimepiride and 0.2-1,250 ng/mL for pioglitazone; the lower limit of quantification (LLOQ) was 0.2 ng/mL for both analytes. Intra- and inter-day reproducibility was less than 10% for glimepiride and less than 5% for pioglitazone, with relative errors ranging from -8.00% to 2.80% at the three concentrations of analytes used for quality control (QC). The matrix effect was negligible and recoveries were similar for each analyte and its IS. Glimepiride and pioglitazone were found to be stable under the assay conditions and the method was successfully applied to the evaluation of pharmacokinetic studies of glimepiride and pioglitazone, following oral doses of 2mg glimepiride tablets and 15 mg pioglitazone tablets to 16 healthy volunteers.

Ultra-performance liquid chromatography electrospray ionization–tandem mass spectrometry method for the simultaneous determination of itraconazole and hydroxy itraconazole in human plasma

A highly sensitive, selective, and precise ultra-performance liquid chromatography tandem mass spectrometry method was developed and validated for simultaneous quantification of itraconazole and hydroxy itraconazole in human plasma by a single liquid–liquid extraction step. The precursor to product ion transitions of m/z 705.3/392.3, m/z 721.2/408.3 and m/z 708.2/435.4 were used to detect and quantify itraconazole, hydroxy itraconazole and itraconazole-d3 respectively. The lower limit of quantitation was found to be 0.500ng/mL for itraconazole and 1.00ng/mL for hydroxy itraconazole. The mean recoveries for itraconazole and hydroxy itraconazole were found to be 100.045% and 100.021%, respectively. This developed method with a chromatographic run time of 2.0min was successfully applied to a bioequivalence study of 100mg itraconazole capsule.

Development and validation of liquid chromatography–tandem mass spectrometry method for simultaneous determination of four tertiary alkaloids in rat plasma and its application to a pharmacokinetic study

A specific and reliable liquid chromatography–electrospray ionization-tandem mass spectrometry method was developed for the simultaneous determination of tetrahydropalmatine (THP), tetrahydroberineper (THB), tetrahydrocoptisine (THC) and corydaline (CDL) in rat plasma using jatrorrhizine as internal standard. Plasma samples were pretreated by protein precipitation with acetonitrile. Chromatographic separation was performed on a Zorbax Eclipse Plus C18 column (3.0mm×100mm, 1.8μm) with gradient elution using acetonitrile–0.1% formic acid water as mobile phase at a flow rate of 0.3mL/min. The detection was carried out by a triple–quadrupole tandem mass spectrometer in multiple-reaction monitoring mode. The mass transition ion-pair was followed as m/z 356.2→192.1, m/z 324.1→176.0, m/z 340.1→176.0, and m/z 370.3→192.1 for THP, THC, THB and CDL. Linear calibration curves were obtained over the range of 0.2–2000ng/mL, and the method limits were 2.0ng/mL for THC, 0.2ng/mL for THB, 1.0ng/mL for THP, and 0.4ng/mL for CDL, respectively. The mean recovery of the analytes ranged from 85.51% to 93.99%. The intra- and inter-day precisions were in the range of 1.21–4.73% and the accuracies were between 92.23% and 98.23%. The validated method was successfully applied to a pharmacokinetic study of THP, THB, THC and CDL in rat plasma following oral administration of Jitai tablet.

Evidence for nevirapine bioactivation in man: Searching for the first step in the mechanism of nevirapine toxicity

Despite its efficacy, including in the prevention of vertical transmission, the antiretroviral nevirapine is associated with severe idiosyncratic hepatotoxicity and skin rash. The mechanisms underlying nevirapine toxicity are not fully understood, but drug bioactivation to reactive metabolites capable of forming stable protein adducts is thought to be involved. This hypothesis is based on the paradigm that drug reactive metabolites have the potential to bind to self-proteins, which results in drug-modified proteins being perceived as foreign by the immune system. The aim of the present work was to identify hemoglobin adducts in HIV patients as biomarkers of nevirapine haptenation upon bioactivation. The ultimate goal is to develop diagnostic methods for predicting the onset of nevirapine-induced toxic reactions.All included subjects were adults on nevirapine-containing antiretroviral therapy for at least 1month. The protocol received prior approval from the Hospital Ethics Committees and patients gave their written informed consent. Nevirapine-derived adducts with the N-terminal valine of hemoglobin were analyzed by an established liquid chromatography–electrospray ionization-tandem mass spectrometry method and characterized on the basis of retention time and mass spectrometric fragmentation pattern by comparison with adduct standards prepared synthetically. The nevirapine adducts were detected in 12/13 patient samples, and quantified in 11/12 samples (2.58±0.8fmol/g of hemoglobin).This work represents the first evidence of nevirapine-protein adduct formation in man and confirms the ability of nevirapine to modify self-proteins, thus providing clues to the molecular mechanisms underlying nevirapine toxicity. Moreover, the possibility of assessing nevirapine-protein adduct levels has the potential to become useful for predicting the onset of nevirapine-induced adverse reactions.

Determination of Free and Total Piperacillin–Tazobactam in Plasma by HPLC–MS–MS: An Adapted Method for Neonates

A sensitive and specific liquid chromatography electrospray ionization-tandem mass spectrometry method for determination of total and free piperacillin–tazobactam in human plasma has been developed and validated. Plasma deproteinization was achieved with Amicon® Ultra-0.5 mL centrifugal filter device (Millipore, Bedford, USA). Chromatography was performed on a Capcell Pak C18 MG column (ID 2 mm × 100 mm, 5 μm, Shiseido, Kyoto, Japan) with isocratic elution using a mobile phase containing water and acetonitrile with an addition of 0.02% of formic acid. Detection was achieved by an Applied Biosystems API 3000 triple quadrupole mass spectrometer (ABI-SCIEX, Toronto, Canada). Electrospray ionization (ESI) was used for ion production. The limits of quantification were 100 ng mL−1 for piperacillin and 30 ng mL−1 for tazobactam. The precision and accuracy for both intra- and inter-day determination of piperacillin ranged from 2.8 to 9.1% and from 94.9 to 104.4%. The precision and accuracy for intra- and inter-day determination of tazobactam ranged from 2.9 to 9.3% and from 88.9 to 99.8%. The precision and accuracy for intra- and inter-day determination of free piperacillin ranged from 4.4 to 14.7% and from 89.0 to 109.6%. The precision and accuracy for intra- and inter-day determination of free tazobactam ranged from 2.8 to 14.4% and from 93.9 to 108.0%. Fifty and 150 μL plasma were used for total and free piperacillin–tazobactam analysis, respectively. The validation results of this analytical method made it feasible for being used in a further pilot study of population pharmacokinetics of piperacillin–tazobactam in neonates.

A sensitive, fast and accurate liquid chromatography–electrospray ionization-tandem mass spectrometry (LC–MS/MS) method for the pharmacokinetic study of cyclobenzaprine tablets

A simple, fast and accurate liquid chromatography–electrospray ionization-tandem mass spectrometry method was developed and validated for the quantification of cyclobenzaprine in human plasma. After a simple single-step liquid–liquid extraction with ethyl acetate, the analyte was separated in an Intersil ODS-3 column through isocratic elution with methanol–water containing 0.1% formic acid (80:20, v/v) at a flow rate of 0.2 ml/min and analyzed by mass spectrometry in the positive ion MRM mode. Good linearity was achieved from 0.04 to 50 ng/ml. The intra- and interday precisions were less than 12.1%, and accuracy ranged from 99.6 to 106.2%. The elimination half-lives (t1/2 Z) after a single oral administration of 5, 10, and 15 mg cyclobenzaprine tablets were 25.5, 26.2, and 26.4 h, respectively. The means ofCmax and AUC increased proportionally to the cyclobenzaprine doses. The pharmacokinetics of cyclobenzaprine fit the linear dynamics of the cyclobenzaprine dose range in healthy Chinese volunteers. Key words: Cyclobenzaprine, liquid chromatography, electrospray ionization, tandem mass spectrometry.

Ultra‐performance liquid chromatography electrospray ionization–tandem mass spectrometry method for the estimation of miglitol in human plasma using metformin as the internal standard

A rapid and sensitive method for the determination of miglitol in human plasma was developed using ultra-performance liquid chromatographic separation with tandem mass spectrometry detection. The preparation of samples required a deproteinization step with acetonitrile. Chromatography was performed on a 5 µ (50 mm × 4.6 mm, ID.) C18 inertsil column, with the mobile phase consisting of acetonitrile 2 mM and ammonium acetate (pH 3.5) with formic acid. Detection was performed using an Applied Biosystems Sciex API 2000 mass spectrometer set at unit resolution in the multiple reaction monitoring mode. Electrospray ionization was used for ion production. The mean recovery of miglitol was 88.9%, with the lower limit of quantification set at 150 ng/mL. Linearity was established for concentrations in the range of 150-4000 ng/mL, with a coefficient of determination (r(2) ) of 0.9981. This assay method makes use of the increased sensitivity and selectivity of tandem mass spectrometric detection, resulting in high-throughput analysis of miglitol for bioequivalence studies.

Application of a liquid chromatography/tandem mass spectrometry method to pharmacokinetic study of mangiferin in rats

A simple, rapid and accurate liquid chromatography–electrospray ionization-tandem mass spectrometry method was developed and validated for quantification of mangiferin in rat plasma. After the addition of the internal standard (IS) paracetamol, plasma samples were pretreated by protein precipitation. Chromatographic separation was carried out on a C 18 column by isocratic elution with methanol–acetonitrile–1% acetic acid (40:3:57, v/v/v). The detection was performed on a Sciex API 3000 LC/MS/MS with TurboIonSpray ionization (ESI) inlet in the positive ion MRM mode. Good linearity was achieved over the concentration range of 3.01–601 ng/mL. Intra- and inter-day precisions were less than 9.1%, and accuracy ranged from 100.5% to 104.0%. The pharmacokinetic profiles of free mangiferin at three dose levels and mangiferin in Zhimu decoction and Zhimu–Huangbai decoction were studied for the first time in rats by this method. After single intragastric administration of free mangiferin 17.5, 35 and 70 mg/kg, C max and AUC increased but non-proportional to the doses. At the same dose level (35 mg/kg), C max and AUC of mangiferin in two decoctions were significantly higher than the corresponding values of free mangiferin.

Determination of free and glucuronidated kaempferol in rat plasma by LC–MS/MS: Application to pharmacokinetic study

Flavanoid kaempferol is mainly present as glucuronides and sulfates in rat plasma, and small amounts of the intact aglycone are also detected. In the this study, a rapid, specific and sensitive liquid chromatography–electrospray ionization-tandem mass spectrometry method (HPLC–MS/MS) was developed and validated for determination of kaempferol and its major metabolite glucuronidated kaempferol in rat plasma. A liquid–liquid extraction with acetic ether was involved for the extraction of kaempferol and internal standard. Analytes were separated on a C18 column (150 mm × 2.1 mm, 4.5 μm, Waters Corp.) with isocratic elution at a flow-rate of 0.3 ml min −1. The mobile phase was consisted of 0.5% formic acid and acetonitrile (50:50, v/v). The Quattro Premier HPLC–MS/MS was operated under the multiple reaction-monitoring mode (MRM) using the electrospray ionization technique. The method was validated according to the FDA guidelines for validation of bioanalytical method. The validated method was successfully applied to the study of the pharmacokinetics in rats after oral administration of kaempferol with different doses.

Simultaneous determination of nicotinic acid and its four metabolites in rat plasma using high performance liquid chromatography with tandem mass spectrometric detection (LC/MS/MS)

A sensitive and specific liquid chromatography electrospray ionization–tandem mass spectrometry method for the simultaneous quantitation of nicotinic acid (NicA) and its metabolites nicotinamide (NA), 1-methylnicotinamide (MNA), 1-methyl-2-pyridone-5-carboxamide (M2PY) and 1-methyl-4-pyridone-5-carboxamide (M4PY) in rat plasma has been developed and validated. As an internal standard, 6-chloronicotinamide was used. The samples (100 μL) were subjected to deproteinization with acetonitrile (200 μL) and then, after centrifugation, 150 μL of the supernatant was transferred into conical vial and evaporated. Dry residue was reconstituted in 100 μL of the ACN/water (10:90, v/v) mixture. Chromatography was performed on a Waters Spherisorb ® 5 μm CNRP 4.6 × 150 mm analytical column with gradient elution using a mobile phase containing acetonitrile and water with 0.1% of formic acid. The full separation of all compounds was achieved within 15 min of analysis. Detection was performed by an Applied Biosystems MDS Sciex API 2000 triple quadrupole mass spectrometer set at unit resolution. The mass spectrometer was operated in the selected reactions monitoring mode (SRM), monitoring the transition of the protonated molecular ions m/ z 153–110 for M2PY, 153–136 for M4PY, 124–80 for NicA, 123–80 for NA and 137–94 for MNA. The mass spectrometric conditions were optimized for each compound by continuously infusing the standard solution at the rate of 5 μL/min using a Harvard infusion pump. Electrospray ionization (ESI) was used for ion production. The instrument was coupled to an Agilent 1100 LC system. The precision and accuracy for both intra- and inter-day determination of all analytes ranged from 1.3% to 13.3% and from 94.43% to 110.88%. No significant matrix effect (ME) was observed. Stability of compounds was established in a battery of stability studies, i.e. bench-top, autosampler and long-term storage stability as well as freeze/thaw cycles. The method proved to be suitable for various applications. In particular using this method we detected increased concentration of MNA and its metabolites in rat plasma after treatment with exogenous MNA (100 mg/kg), as well as increased concentration of endogenous NA and MNA in rat plasma in the early phase of hypertriglyceridemia development in rats fed high-fructose diet.

Determination of cymipristone in human plasma by liquid chromatography–electrospray ionization-tandem mass spectrometry

A rapid, specific and sensitive liquid chromatography–electrospray ionization-tandem mass spectrometry method was developed and validated for determination of cymipristone in human plasma. Mifepristone was used as the internal standard (IS). Plasma samples were deproteinized using methanol. The compounds were separated on a ZORBAX SB C 18 column (50 mm × 2.1 mm i.d., dp 1.8 μm) with gradient elution at a flow-rate of 0.3 ml/min. The mobile phase consisted of 10 mM ammonium acetate and acetonitrile. The detection was performed on a triple-quadruple tandem mass spectrometer by selective reaction monitoring (SRM) mode via electrospray ionization. Target ions were monitored at [M+H] + m/ z 498 → 416 and 430 → 372 in positive electrospray ionization (ESI) mode for cymipristone and IS, respectively. Linearity was established for the range of concentrations 0.5–100 ng/ml with a coefficient correlation ( r) of 0.9996. The lower limit of quantification (LLOQ) was identifiable and reproducible at 0.5 ng/ml. The validated method was successfully applied to study the pharmacokinetics of cymipristone in healthy Chinese female subjects.

Application of a liquid chromatography/tandem mass spectrometry method for the pharmacokinetic study of dihydroartemisinin injectable powder in healthy Chinese subjects

A simple, rapid and accurate liquid chromatography–electrospray ionization-tandem mass spectrometry method was developed and validated for quantification of dihydroartemisinin (DHA) in human plasma. Following a simple single-step liquid–liquid extraction with ethyl acetate, the analyte was separated on a C 18 column by isocratic elution with methanol–water–10 mM ammonium acetate (80:10:10, v/v/v), and analyzed by mass spectrometry in the positive ion MRM mode. Good linearity was achieved over a wide range of 1.01–2020 ng/mL. Intra- and inter-day precisions were less than 9.0%, and accuracy ranged from 93.0 to 98.2%. The pharmacokinetics of DHA injectable powder was studied for the first time in healthy subjects by this method. After single intravenous infusion of DHA injectable powder 40, 80 and 160 mg, the elimination half-life ( t 1/2 λZ ) was 1.69, 1.88 and 1.92 h, respectively; mean C max and AUC increased in proportion to the doses. The pharmacokinetics of DHA fit the linear dynamic feature over the DHA dose range studied.

A rapid and highly sensitive method for the determination of glimepiride in human plasma by liquid chromatography–electrospray ionization tandem mass spectrometry: application to a pre‐clinical pharmacokinetic study

A sensitive and specific liquid chromatography-positive electrospray ionization-tandem mass spectrometry method has been developed and validated for the determination of glimepiride (GPD) in human plasma. GPD and the internal standard (IS, glibenclamide) were extracted from a small aliquot of human plasma (200 microL) by a simple liquid-liquid extraction technique using ethyl acetate as extraction solvent. The compounds were separated on a YMC Propack, C18, 4.6x50 mm column using a mixture of ammonium acetate buffer, acetonitrile and methanol (30:60:10, v/v) as mobile phase at 0.5 mL/min on an API 4000 Sciex mass spectrometer connected to an Agilent HPLC system. Method validation and pre-clinical sample analysis was performed as per FDA guidelines and the results met the acceptance criteria. GPD and IS were detected without any interference from human plasma matrix. The method was proved to be accurate and precise at linearity range of 0.02-100.00 ng/mL with a correlation coefficient of 0.999. The method was robust with a lower limit of quantitation of 0.02 ng/mL. Intra- and inter-day accuracies for GPD were 88.60-113.50 and 96.82-103.93%, respectively. The inter-day precision was better than 12.21%. This method enabled faster and reliable determination of GPD in a pre-clinical study.

Application of liquid chromatography—Tandem mass spectrometry method for the analysis of new nonselective β‐adrenergic blocker 1‐(1‐H‐indol‐4‐yloxy)‐3‐{[2‐(2‐methoxy phenoxy)ethylo]amino}propan‐2‐ol (2F109) in rat plasma

A sensitive and specific liquid chromatography electrospray ionization-tandem mass spectrometry method for the enantioselective determination of the novel beta-adrenolytic compound, 1-(1-H-indol-4-yloxy)-3-{[2-(2-methoxyphenoxy)ethylo]amino} propan-2-ol, in rat plasma has been developed and validated. Chromatography was performed on a reversed-phase Chiralcel OD-RH analytical column (150x4.6 mm, 5 microm, Daicel Chemical Industries, Tokyo, Japan) with isocratic elution using a mobile phase containing acetonitrile and water with 0.01% formic acid. Detection was achieved by an Applied Biosystems MDS Sciex (Concord, Ontario, Canada) API 2000 triple quadrupole mass spectrometer. Electrospray ionization (ESI) was used for ion production. The limit of detection in the MRM mode was found to be 1.25 ng/ml. The limit of quantification of both enantiomers was 2.5 ng/ml. The precision and accuracy for both intra- and inter-day determination of 2F109 enantiomers ranged from 2.6 to 12% and from 89.1 to 107.1%. This analytical method allowed us to carry out pharmacokinetic studies in rats. Our findings demonstrate that 2F109 shows stereoselective disposition in rat plasma after i.v. administration. The terminal half-lives of (+)-(R)-2F109 and (-)-(S)-2F109 were 33.5 and 42.6 min, respectively. The AUC0-inf of (+)-(R)-2F109 exceeded that of (-)-(S)-2F109.