Determination of Chlorzoxazone in Rat Plasma by LC-ESI-MS/MS and Its Application to a Pharmacokinetic Study

A sensitive LC-ESI-MS/MS method for determination of chlorzoxazone in rat plasma has been developed. Chromatographic separation was achieved on a Zorbax SB-C₁₈ column, with 45:55 (v/v) acetonitrile–water as the mobile phase. A LC-ESI-MS/MS was performed in a multiple reactions monitoring (MRM) mode using target ions m/z 167.5→131.6 for chlorzoxazone and m/z 230.7→185.6 for phenobarbital (internal standard). The calibration plots were linear over the range of 10.0–2,000 ng/mL. Intra-day and inter-day precisions were better than 5.1% and 6.8%, respectively. The validated method was successfully used to analyze the drug in samples of rat plasma for pharmacokinetic study.     

LC Method for Analysis of Three Flavonols in Rat Plasma and Urine after Oral Administration of Polygonum aviculare Extract

A high-performance liquid chromatographic method has been developed for the simultaneous analysis of the flavonols myricitrin (1), avicularin (2), and juglanin (3) in rat plasma and urine after oral administration of the total flavonoids from Polygonum aviculare. Samples were prepared by solid-phase extraction then separated on a C₁₈ reversed-phase column by use of a mobile-phase gradient prepared from methanol and aqueous formic acid solution. The flow rate was 1 mL min⁻¹. Detection was performed at 254 nm. The calibration range was 11–1,100 μg mL⁻¹ for both 2 and 3 in plasma; in urine the calibration ranges for 1, 2, and 3 were 32–1,600, 11–1,100, and 22–1,100 μg mL⁻¹, respectively. Intra-day and inter-day RSD were less than 4.33 and 3.62% for 2 and 3, respectively, in plasma, and no more than 4.03 and 2.22% for all the analytes in urine. The analytical sensitivity and selectivity of the assay enabled successful application to pharmacokinetic studies of flavonols 1–3 in rats.

     

LC Method for Analysis of Three Flavonols in Rat Plasma and Urine after Oral Administration of Polygonum aviculare Extract

A high-performance liquid chromatographic method has been developed for the simultaneous analysis of the flavonols myricitrin (1), avicularin (2), and juglanin (3) in rat plasma and urine after oral administration of the total flavonoids from Polygonum aviculare. Samples were prepared by solid-phase extraction then separated on a C₁₈ reversed-phase column by use of a mobile-phase gradient prepared from methanol and aqueous formic acid solution. The flow rate was 1 mL min^?1. Detection was performed at 254 nm. The calibration range was 11–1,100 μg mL^?1 for both 2 and 3 in plasma; in urine the calibration ranges for 1, 2, and 3 were 32–1,600, 11–1,100, and 22–1,100 μg mL^?1, respectively. Intra-day and inter-day RSD were less than 4.33 and 3.62% for 2 and 3, respectively, in plasma, and no more than 4.03 and 2.22% for all the analytes in urine. The analytical sensitivity and selectivity of the assay enabled successful application to pharmacokinetic studies of flavonols 1–3 in rats.     

Enantioselective Separation and Determination of Carnosine in Rat Plasma by Fluorescence LC for Stereoselective Pharmacokinetic Studies

A sensitive fluorescence liquid chromatographic analytical method was developed for the simultaneous determination of carnosine enantiomers in rat plasma. The method was applied to pharmacokinetic studies. Chiral separation of carnosine enantiomers was achieved by pre-column derivatization with o-phthaldialdehyde and the thiol N-acety-l-cysteine as derivating reagents. They were separated on an ODS column and detected by fluorescence detection (λ_ex = 350 nm, λ_em = 450 nm). γ-Aminobutyric acid was used as internal standard. The method was linear up to 6,000 ng mL^?1 for l-carnosine, 4,000 ng mL^?1 for d-carnosine. Low limit of quantitation (LLOQ) was 40 ng mL^?1 for each isomer. The relative standard deviations obtained for intra- and inter-day precision were lower than 12% and the recoveries were higher than 75% for both enantiomers. The method was applied to a stereoselective study on the pharmacokinetics of carnosine after oral administration with a single dose (carnosine, 75 mg kg^?1 for each isomer) to a rat. The initial data indicated that l-carnosine had a larger value of the highest plasma concentration than d-carnosine (C _max 5,344 vs. 1,914 ng mL^?1), and that of l-carnosine had a lower value of AUC_(0?∞) and t _1/2(h) (AUC_(0?∞) 5,306 vs. 6,321 ng h mL^?1, t _1/2 1.43 vs. 3.37 h). Our results indicated that the pharmacokinetic of l-carnosine and d-carnosine revealed enantioselective properties significantly.     

Quantitative determination of perfluorinated surfactants in water by LC-ESI-MS/MS

The surfactants perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), and derivatives of the latter have emerged as globally distributed persistent environmental contaminants. Methods for their reliable quantitative determination at ppt-levels (ng/L) are needed in order to detect their main sources, to elucidate their environmental fate, and to identify potential sinks. The common method for water analysis involves preconcentration by SPE followed by LC coupled to ESI MS/MS (LC-ESI-MS/ MS). All sample preparation steps must be carefully optimized in order to arrive at reliable quantitative data. Two major aspects are important: (i) during SPE, contaminations may arise from materials containing traces of PFOA/S; (ii) during LC-ESI-MS/ MS, ionization yields are suppressed by matrix components and depend upon the analyte concentrations in the extracts. The levels of PFOA/S in the river Roter Main near Bayreuth have been determined using the optimized method.     

Development and Validation of LC-ESI-MS/MS Method for the Determination of Alfuzosin in Human Plasma

Journal of Analytical Chemistry - A new liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) method has been developed and validated for alfuzosin quantification in...     

Determination of Tectorigenin in Rat Plasma: Application to a Pharmacokinetic Study After Oral Administration of Tectorigenin or Its Prodrug Tectoridin

A simple, sensitive, and validated liquid chromatographic method has been developed for the determination of tectorigenin in rat plasma and application to a pharmacokinetic study after oral administration of tectorigenin or its prodrug tectoridin. The analysis was performed on a Kromasil C₁₈ analytical column using gradient elution with acetonitrile 0.1% phosphonic acid water at 0.8 mL min⁻¹. The detection wavelength for UV detection was set at 264 nm. The established method was fully validated with parameters as follows: the intra- and inter-day assay precisions (CV) of three analytes were in the range of 4.2–13.3% and accuracies were between 98.0 and 107.5%; the calibration curve was linear with r ² > 0.99 over a concentration range of 0.02–2 μg mL⁻¹; the lower limit of quantification was 0.02 μg mL⁻¹; tectorigenin showed stable in rat plasma after 12 h incubation at room temperature, 15 days storage at −80 °C and three freeze/thaw cycles, as well as in reconstitute buffer for 24 h at 25 °C; and the mean recoveries of tectorigenin were 92.3 ± 3.2, 95.5 ± 2.9 and 94.5 ± 3.0% with quality control levels of 0.02, 0.2 and 2 μg mL⁻¹, respectively. In conclusion, this method is simple, economic, and sensitive enough for in vivo pharmacokinetic studies of tectorigenin.

     

Determination of Tectorigenin in Rat Plasma: Application to a Pharmacokinetic Study After Oral Administration of Tectorigenin or Its Prodrug Tectoridin

A simple, sensitive, and validated liquid chromatographic method has been developed for the determination of tectorigenin in rat plasma and application to a pharmacokinetic study after oral administration of tectorigenin or its prodrug tectoridin. The analysis was performed on a Kromasil C₁₈ analytical column using gradient elution with acetonitrile 0.1% phosphonic acid water at 0.8 mL min^?1. The detection wavelength for UV detection was set at 264 nm. The established method was fully validated with parameters as follows: the intra- and inter-day assay precisions (CV) of three analytes were in the range of 4.2–13.3% and accuracies were between 98.0 and 107.5%; the calibration curve was linear with r ² > 0.99 over a concentration range of 0.02–2 μg mL^?1; the lower limit of quantification was 0.02 μg mL^?1; tectorigenin showed stable in rat plasma after 12 h incubation at room temperature, 15 days storage at ?80 °C and three freeze/thaw cycles, as well as in reconstitute buffer for 24 h at 25 °C; and the mean recoveries of tectorigenin were 92.3 ± 3.2, 95.5 ± 2.9 and 94.5 ± 3.0% with quality control levels of 0.02, 0.2 and 2 μg mL^?1, respectively. In conclusion, this method is simple, economic, and sensitive enough for in vivo pharmacokinetic studies of tectorigenin.     

超高效液相色谱-串联质谱法同时测定大鼠血浆中阿帕替尼与紫杉醇

建立了同时定量测定大鼠血浆中阿帕替尼和紫杉醇的超高效液相色谱-串联质谱(UPLC-MS/MS)方法,并应用于药动学研究。血浆样品经固相萃取(SPE)处理。色谱柱为Agilent Zorbax Eclipse Plus C18柱(100 mm×2.1 mm,1.8μm),流动相为乙腈-0.1%甲酸溶液,体积流量0.4 m L/min,柱温40℃,进样量为3μL。质谱采用电喷雾正离子源模式(ESI+),多反应监测模式(MRM)进行定量测定。阿帕替尼和紫杉醇在0.5~1 500μg/L范围内均呈良好的线性关系(r2≥0.998),最低定量下限(LLOQ)均为0.5μg/L,日内、日间精密度RSD≤8.4%,准确度为92.5%~107.1%,提取回收率为86.2%~95.1%,基质效应(86.6%~108.6%)不影响待测物血药浓度的测定。经方法学验证,该法快速灵敏,可同时对阿帕替尼和紫杉醇进行血药浓度监测,为临床联合用药研究提供了重要的分析手段。     

Determination of Daphnetin and its 8-O-Methylated Metabolite in Rat Plasma by UFLC-MS/MS: Application to a Pharmacokinetic Study

Daphnetin, which has been developed as a drug against obliterative vasculitis, can be rapidly and stereoselectively metabolized to an active 8-O-methylated metabolite, namely daphnetin 8-methyl ether (daphnetin-Me). Herein, a rapid, sensitive and reliable ultrafast liquid chromatography tandem mass spectrometry (UFLC-MS/MS) method was developed and validated to simultaneously determine daphnetin and daphnetin-Me in rat plasma after intragastric administration. The MS quantification for the two analytes and 3-aminocoumarin (internal standard, IS) was carried out on a triple quadrupole mass spectrometer using an ESI source in positive multiple reaction monitoring mode (daphnetin: m/z 179.15?→?51.10; daphnetin-Me: m/z 193.30?→?150.05; IS: m/z 162.00?→?106.20). The method exhibited a broad linear range of 1–2000 ng mL^?1. The intra- and inter- assay precisions (RSD%) were?≤?8.29% with the accuracies (RME%) within?±?5.95%. This newly developed method was successfully applied to a pharmacokinetic study of daphnetin after a single dose of 20 mg kg^?1 in rats. Daphnetin and daphnetin-Me peaked almost at the same time. Compared with that of daphnetin, a 2.1-fold higher area under the concentration–time curve (AUC) for daphnetin-Me were observed. These results would be beneficial in facilitating further investigation of pharmacological mechanisms, as well as the rational application of daphnetin and daphnetin-containing herb preparations.

     

Determination of Tangeretin in Rat Plasma by LC-Electrospray-Ion Trap MS

A selective, sensitive, and accurate method has been developed and validated for the quantification of tangeretin in rat plasma. The application of LC-electrospray-ion trap mass spectrometry in full scan and multiple reactions monitoring modes were investigated. Following solid phase extraction using a hydrophilic–lipophilic balance cartridge, the analytes were separated on a C₁₈ column using an isocratic mobile phase composed of acetonitrile/water (50:50, v/v) containing 0.3% formic acid. In full scan mode, the LOQ was 2 ng mL^?1. The standard calibration curve was linear (R ² = 0.9999) over the concentration range 2–200 ng mL^?1. The precision over the concentration range was within 15% (RSD) and the accuracy was ranged from 86 to 115%. In multiple reaction monitoring mode, the LOQ was 1 ng mL^?1 and the standard calibration curve was linear (R ² = 0.9976) over the concentration range 1–100 ng mL^?1 with a precision of 12% and accuracy rangeing from 91 to 113%.     

Rapid Determination of Montelukast in Human Plasma by LC-ESI-MS/MS and Its Application to a Bioequivalence Study

Abstract

A rapid liquid chromatography–electrospray ionization–tandem mass spectrometry (LC-ESI-MS/MS) method was developed for the determination of montelukast in human plasma. The extraction of montelukast from plasma (300 µL) involved protein precipitation. Quantitation was performed using LC-ESI-MS/MS, operating in the positive ion and selective reaction monitoring (SRM) mode. The total chromatographic run time for the analysis was 1.5 min. A linear dynamic range was established from 5 to 800 ng mL^?1 for montelukast. The method was fully validated especially with regard to real subject sample analysis. It was successfully applied to a bioequivalence study in 18 healthy human subjects under fed condition (human subjects were allowed to eat as per the prescribed diet for bioequivalence study).     

Validated LC-ESI-MS/MS Method for the Quantitation of Neopanaxadiol: a Novel Neuroprotective Agent from Panax ginseng and Its Application to a Pharmacokinetic Study in Rat Plasma

Neopanaxadiol (NPD), a new panaxadiol first obtained from the acid hydrolysate of the total ginsenosides of Panax ginseng C. A. Meyer (Araliaceae) in our laboratory, showed neuroprotective effect against glutamate-induced neurotoxicity in primary cultures of rat cortical cells (Tao et al. Chin Chem Lett 20:687–689, 2009). In this research, a sensitive and specifical method of ultra-performance liquid chromatography–electrospray mass spectrometry (UPLC-ESI-MS/MS) for the quantitative analysis of NPD in rat plasma was developed. The NPD and internal standard of panaxadiol were extracted from 200 μL of rat plasma samples with methanol, then the samples were injected in an UPLC (Waters BEH) with C18 column (50 mm × 2.1 mm i.d., 1.7 μm) and eluted with the mobile phase consisting of methanol–water–formic acid (80:20:0.2, v/v/v). Excellent linearity was found between 5 and 160 ng mL^?1 with a limit of quantitation of 4 ng mL^?1. Intra- and inter-day precision values (RSD) of QC samples were both below 7 %. This study was successfully utilized for the pharmacokinetic profiles of NPD in rats after oral administration and provided an experimental basis for the further pharmacology and clinical application of ginseng products.     

Determination of Leuprolide–Fatty Acid Conjugate in Rat Plasma Using LC-MS/MS and Its Pharmacokinetics after Subcutaneous Administration in Rats

Leuprolide is a synthetic nonapeptide drug (pyroGlu-His-Trp-Ser-Tyr-d-Leu-Leu-Arg-Pro-NHEt) that acts as a gonadotropin-releasing hormone agonist. The continuous administration of therapeutic doses of leuprolide inhibits gonadotropin secretion, which is used in androgen-deprivation therapy for the treatment of advanced prostate cancer, central precocious puberty, endometriosis, uterine fibroids, and other sex-hormone-related conditions. To improve the pharmacokinetic properties of peptide drugs, a fatty acid was conjugated with leuprolide for long-term action. In this study, we developed a simple ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous determination of leuprolide and leuprolide–oleic acid conjugate (LOC) levels. The developed method was validated in terms of linearity, precision, accuracy, recovery, matrix effect, and stability according to the US Food and Drug Administration guidelines, and the parameters were within acceptable limits. Subsequently, the pharmacokinetics of leuprolide and LOCs were evaluated. In vivo rat subcutaneous studies revealed that conjugation with fatty acids significantly altered the pharmacokinetics of leuprolide. After the subcutaneous administration of fatty-acid-conjugated leuprolide, the mean absorption time and half-life were prolonged. To the best of our knowledge, this is the first study showing the effects of fatty acid conjugates on the pharmacokinetics of leuprolide using a newly developed UPLC-MS/MS method for the simultaneous quantification of leuprolide and LOCs.     

Determination of Camptothecin and 10-Hydroxycamptothecin in Camptotheca acuminata by LC-ESI-MS/MS

A rapid and sensitive liquid chromatography-tandem mass spectrometry method with multiple reaction monitoring was developed for the simultaneous determination of camptothecin and 10-hydroxycamptothecin in Camptotheca acuminata. The separation of camptothecin and 10-hydroxycamptothecin was performed on an Agilent Eclipse XDB-C18 column with a mixture of methanol and water (1:1, v/v) containing 0.2% formic acid as a mobile phase. The limits of detection of camptothecin and 10-hydroxycamptothecin were 4.0 ng/mL and 7.0 ng/mL (S/N = 3), respectively. Analysis took 10 minutes, making the method suitable for rapid determination of camptothecin and 10-hydroxycamptothecin in C. acuminata.     

Quantitative Determination of Octylonium in Human Plasma by LC–MS

The purpose of this investigation was to develop a method for measuring the concentration of octylonium in human plasma. Hydrochloric acid was added to the plasma samples before pretreatment to improve the stability of the octylonium. After liquid–liquid extraction with ethylacetate and isopropanol (10:1), the analytes were separated by chromatography on a reversed-phase C₁₈ column and detected by LC–MS–MS with electrospray ionization–ionization. The coefficient of variation for the precision of the assay was less than 10.1%, and the accuracy ranged from 98.0 to 106.5%. The limit of quantification or sensitivity was 0.2 ng mL⁻¹. This method was validated by measuring octylonium in the plasma of healthy human subjects after administration of a single 120-mg oral dose of octylonium bromide. Thus, a highly sensitive and accurate analytical method was developed to determine the concentration of octylonium in human plasma.     

LC–MS Determination and Pharmacokinetic Study of a Novel Sulfonylurea: Potential Hypoglycemic Agent in Rat Plasma

To support preclinical pharmacokinetic investigation of 1-[4-[2-(4-bromobenzene-sulfonaminoethyl)phenylsufonyl]-3-(trans-4-methylcyclohexyl)urea (G004), a rapid, sensitive and specific high-performance liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS) method was developed and validated. Glibenclamide was employed as internal standard. After liquid–liquid extraction the analyte was analyzed on a Kromasil C₁₈ column (150 × 2.0 mm i.d.) with a mobile phase consisted of acetonitrile–water (0.05% acetic acid), 30:70 (v/v). The flow rate was 0.2 mL min⁻¹. Detection was performed on a quadrupole mass spectrometer using an electrospray ionization interface and the selected-ion monitoring (SIM) mode. The retention time was about 3.5 and 4.2 min for Glibenclamide and G004, respectively. The assay was linear over the concentration range of 2.0–500.0 ng mL⁻¹. Extraction Recovery of G004 in rat plasma was more than 87%. The intra- and inter-assay precision was lower than 11.5% (CV). This validated method was successfully applied to the pharmacokinetics of G004 in rats.     

LC Method for the Determination of Rhaponticin in Rat Plasma, Faeces and Urine for Application to Pharmacokinetic Studies

A simple liquid chromatography (LC) method has been developed and validated to determine rhaponticin in rat plasma, faeces and urine. Chromatographic separation was achieved through mobile phase consisting of acetonitrile and water at a flow rate of 1.0 mL min^?1. Rhaponticin was quantified using UV detection at 324 nm. The assay was linear over the concentration range of 50–4,000 ng mL^?1 for plasma, faeces and urine. The intra- and inter-day RSD were less than 10%. The plasma, faeces and urine rhaponticin levels were monitored in rats after oral administration. This simple LC method appears to be useful in the pharmacokinetic investigation of rhaponticin.     

Determination of Tiopronin in Human Plasma and Pharmacokinetics by LC-ESI-MS

A rapid, sensitive and specific method based on high performance liquid chromatography-electrospray ionization-mass spectrometry was developed for the determination of tiopronin in human plasma. In this study, vitamin C and dithiothreitol were used as the reducer and to release and stabilize tiopronin from dimeric mixed forms with endogenous thiols encountered during pretreatment of plasma samples. The separation was successfully achieved on an Agilent SB-Aq column packed with 5 μm C₁₈ silica, using an aqueous formic acid solution (pH 4.5–4.7), 0.5 mM tris(hydroxymethyl)aminomethane and methanol (95:5, v/v) as the mobile phase. Mass spectra were acquired in selective ion monitoring mode, using the [M ? H] ^? ions of tiopronin at m/z 162.0 and the [M ? H]^? of the internal standard sodium cyclamate at m/z 178.0, respectively. This quantitative assay was fully validated with respect to precision, repeatability and accuracy. The correlation coefficients were >0.9995 in the range 0.025–8.15 μg mL^?1 in human plasma. The mean recoveries were above 85%. The limit of quantitation was 0.012 μg mL^?1 with a relative standard deviation of inter-day and intra-day accuracy of less than 15%. This LC-ESI-MS method was also successfully applied to a pharmacokinetic study after oral administration of formulated tiopronin to healthy volunteers. The elimination half-life (T _1/2) was 21.5 ± 11.1 h.