Development and validation of a high-performance liquid chromatographic method for determination of pinocembrin in rat plasma: Application to pharmacokinetic study

A sensitive and specific reversed-phase high-performance liquid chromatography with ultraviolet detection (RP-UV-HPLC) method has been developed and validated for the identification and quantification of pinocembrin in rat plasma using chrysin as the internal standard. Following protein precipitation with acetonitrile, the analytes were separated by the mobile phase 0.01 M ammonium acetate (pH 4.0)–methanol (35:65, v/v) with an Agilent TC-C18 column (5 μm, 4.6 mm × 150 mm) at a flow rate of 1 ml/min, column temperature 40 °C and detection wavelength 290 nm. A good linear relationship was obtained in the concentration range studied (0.07–133.33 μg/ml, r = 0.9995). The lowest limit of quantification (LLOQ) was 66.7 ng/ml and the lowest limit of detection (LLOD) was 25 ng/ml. Average recoveries ranged from 93.9 to 97.8% in plasma at the concentrations of 0.33 and 33.33 μg/ml. Intra- and inter-batch relative standard deviations were 0.15–2.03 and 1.18–9.96%, respectively. This method was successfully applied to the pharmacokinetic studies in rats after intravenous administration of pinocembrin.     

Development and validation of indirect RP-HPLC method for enantiomeric purity determination of D-cycloserine drug substance

A new chiral purity method was developed for D-cycloserine (D-cys) by reverse phase HPLC and validated. Chiral derivatizing reagents, viz., o-phthalaldehyde and N-acetyl-L-cysteine were utilized in this method. The resultant diastereomers were resolved using Zorbax SB Phenyl HPLC column under isocratic elution. A mobile phase of 95:05 (v/v), 20mM Na(2)HPO(4) (pH 7), and acetonitrile, respectively, was used with the flow rate of 1.0 mL/min and UV detection at 335 nm. The method development with different chiral stationary phases and chiral derivatization reagents were also investigated. The stability of diastereomer derivative and influence of organic modifier and pH of the mobile phase were studied and optimized. The stability-indicating capability of the method was established by performing stress studies under acidic, basic, oxidation, light, humidity and thermal conditions. The detection and quantitation limit of L-cycloserine (L-cys) were 0.015 and 0.05% (w/w), respectively. A linear range from 0.05 to 0.30% (w/w) was obtained with the coefficient of determination (r(2)) 0.998. The recovery obtained for L-cys was between 92.9 and 100.2%. This method was applied successfully in pharmaceutical analysis to determine the content of L-cys in D-cys bulk drug.     

利巴韦林的含量测定以及人体药代动力学分析

本文建立了简单、快速的HPLC方法测定利巴韦林在人血浆中的含量, 并研究了健康受试者体内利巴韦林片剂的药代动力学。HPLC方法选择C18色谱柱（250mm×4.6mm,5μm）, 超纯水为流动相, 柱温为25°C, 检测波长为207nm。在50.4-2016.0ng/mL范围内线性关系良好（r=0.9998）, 最低检测浓度为15ng/mL。低、中、高三个浓度的相对回收率大于90%, 日内精密度小于10%, 日间精密度小于15%。用药代动力学软件WinNonlin进行房室模型分析的结果显示：二室模型能更好地模拟利巴韦林在体内的过程。计算得到的AUC0-t、CL/F和Cmax分别是10807.8 h·ng/mL、64879.5 mL和525.1ng/mL。这些结果为药剂工作者开发利用利巴韦林剂型提供了参考。     

Development of a high performance liquid chromatography method for quantification of PAC-1 in rat plasma

A sensitive and specific high performance liquid chromatography method with UV detection was developed and validated for the determination of PAC-1 in rat plasma. After extraction with ethyl acetate, the chromatographic separation was carried out on a Diamonsil C₁₈ column (150 mm × 4.6 mm i.d., 5 μm particle size, Zhonghuida) protected by a ODS guard column (10 mm × 4.6 mm i.d., 5 μm particle size), using acetonitrile–methanol–phosphate buffer (pH 3.0, 30 mM) (31:3:66, v/v/v) as mobile phase at a flow rate of 1.0 mL/min, and wavelength of the UV detector was set at 281 nm. No interference from any endogenous substances was observed during the elution of PAC-1 and internal standard (IS, indapamide). The calibration curve was linear over the range of 0.05–20 μg/mL (r > 0.99). The lower limit of quantification was evaluated to be 50 ng/mL. The method was successfully applied to the pharmacokinetic study of PAC-1 after intravenous and oral administration in rats, respectively.     

高效液相色谱法测定大鼠血浆中的西他列汀浓度及其药动学研究(英文)

本研究建立并验证了测定大鼠血浆中磷酸西他列汀浓度的高效液相色谱法,并在大鼠体内进行药动学研究。血浆中的药物和内标(氢化可的松)由乙酸乙酯萃取。所用色谱柱为Agilent Zorbax Extend-C18柱(250mm×4.6mm,4μm),进样量为20μL,检测波长为267nm,柱温为30oC。流动相为甲醇–水(60:40,内含10mMTris和10mM三乙胺,并用1M盐酸调至pH9.0)。流速为1.0mL/min。色谱峰具有良好的特异性。在0.75–100.0μg/mL范围内具有良好的线性关系(r>0.9957)。定量下限为0.75μg/mL。日间,日内精密度均小于10%。在0.75,10.0,100.0μg/mL的相对回收率为105.3%,99.8%,99.0%,提取回收率分别为81.5%,82.4%,84.5%。样品的稳定性良好。运用该方法测定了大鼠口服磷酸西他列汀水溶液后的血药浓度,说明本方法可用于药物动力学的研究。     

Development and validation of a rapid HPLC- fluorescence method for simultaneous determination of venlafaxine and its major metabolites in human plasma

Background and the purpose of the study

To develop a simple, rapid and accurate HPLC method for the measurement of the venlafaxine and its main metabolites, O-desmethylvenlafaxine and O,N-didesmethylvenlafaxine in pharmacokinetic studies and therapeutic drug monitoring.

Method

Chromatographic separation was achieved with a ChromolithTM Performance RP-18e 100 mm×4.6 mm column equipped with a Fluorescence detectore (λ_ex 200 nm/λ_em 300 nm) The mobile phase of methanol:water (35:65, v/v) adjusted to pH 2.5 by phosphoric acid was passed through the column in an isocratic mode at flow rate of 2 ml/min. The sample preparation involved a simple, one-step, extraction with ethyl acetate.

Results

The calibration curves were linear in the concentration range of 1-300 ng/ml for all analytes (r2>0.998). The lower limit of quantification was 1 ng/ml for all analytes. Within and between day precisions in the measurement of quality control (QC) of samples were in the range of 1.8-14.1% for all analytes.

Conclusion

The developed procedure was used to assess the pharmacokinetics of venlafaxine and its main metabolites following oral administration of 75 mg venlafaxine to a healthy subject.     

Development and validation of a high-performance liquid chromatographic method for bioanalytical application with rimonabant

A simple and feasible high-performance liquid chromatographic method with UV detection was developed and validated for the quantification of rimonabant in human plasma. The chromatographic separation was carried out in a Hypersil BDS, C₁₈ column (250 mm × 4.6 mm; 5 μm). The mobile phase was a mixture of 10 mM phosphate buffer and acetonitrile (30:70, v/v) at a flow rate of 1.0 ml/min. The UV detection was set at 220 nm. The extraction recovery of rimonabant in plasma at three quality control (QC) samples was ranged from 84.17% to 92.64%. The calibration curve was linear for the concentration range of 20–400 ng/ml with the correlation coefficient (r²) above 0.9921. The method was specific and sensitive with the limit of quantification of 20 ng/ml. The accuracy and precision values obtained from six different sets of QC samples analyzed in separate occasions ranged from 88.13% to 106.48% and 0.13% to 3.61%, respectively. In stability tests, rimonabant in human plasma was stable during storage and assay procedure. The method is very simple, sensitive and economical and the assay was applied to human plasma samples in a clinical (pharmacokinetic) study of rimonabant.     

Comparative evaluation between capillary electrophoresis and high-performance liquid chromatography for the analysis of florfenicol in plasma

A capillary electrophoresis (CE) and a reversed phase high-performance liquid chromatography (RP-HPLC) method with UV detection have been developed for florfenicol analysis in plasma samples. The suitabilities of both methods for quantitative determination of florfenicol were approved through validation specification, such as linearity, precision, selectivity, accuracy, limit of detection and quantification. The capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) assay were compared by analyzing a series of plasma samples containing florfenicol in different concentrations using the two methods. The extraction procedure is simple and no gradient elution or derivatization is required. Furthermore, the analysis time of the CE method is two times shorter than the respective parameter in HPLC and solvent consumptions is considerably lower. The calibration curve were linear to at least 0.05–10 μg/ml (r = 0.9998) and 0.1–10 μg/ml (r = 0.9998) for CE and HPLC, respectively. The separation efficiency are good for both methods. The detection limits for florfenicol were 0.015 μg/ml with CE and 0.03 μg/ml with HPLC and CE method gave lower value, even though UV detector was applied in the both cases. The both methods were selective, robust and reliable quantification of florfenicol and can be useful for clinical and biomedical investigations.     

Development and validation of a LC-MS/MS method with electrospray ionization for determination of LASSBio-579 in rat plasma

A simple and sensitive LC-MS/MS analytical method was developed and validated for the determination of LASSBio-579 in plasma rat, using fluconazole as internal standard. Analyses were performed on a Shimadzu HPLC system using a Shimadzu C18 column and isocratic elution with acetonitrile-water (80:20, v/v), containing 0.4mM ammonium hydroxide and 0.2 mM acetic acid at a flow rate of 1.0 ml/min (split ratio 1:5). A Micromass triple quadrupole mass spectrometer, equipped with an electrospray ionization interface, operated in the positive mode. Plasma samples were deproteinized with acetonitrile (1:2) and 50 microl of the supernatant were injected into the system. The retention times of LASSBio-579 and IS were approximately 4.7 and 2.4 min, respectively. Calibration curves in spiked plasma were linear over the concentration range of 30-2000 ng/ml with determination coefficient >0.98. The lower limit of quantification was 30 ng/ml. The accuracy of method was within 15%. Intra- and inter-day relative standard deviations were less or equal to 13.5% and 6.4%, respectively. The applicability of the LC-MS/MS method for pharmacokinetic studies was tested using plasma samples obtained after intraperitoneal administration of LASSBio-579 to male Wistar rats. No interference from endogenous substances was observed, showing the specificity of the method developed. The reported method can provide the necessary sensitivity, linearity, precision, accuracy, and specificity to allow the determination of LASSBio-579 in pre-clinical pharmacokinetic studies.     

New bioanalytical microemulsion Electrokinetic chromatography method for the simultaneous determination of Trifluridine with its metabolites and Tipiracil in rat plasma: Application to pharmacokinetic studies

A Microemulsion Electrokinetic Chromatography method coupled with diode array detector (MEEKC-DAD) was developed for the first time and found to be efficient, sensitive, and selective for the simultaneous analysis of Trifluridine (FTD), and its metabolites 5-(trifluoromethyl) uracil (FTY) and 5-carboxy-2′-deoxyuridine (5CDU), and Tipiracil (TIP) in rat plasma. Sample pre-treatment involved a simple protein precipitation from plasma using acetonitrile. The separation was achieved using a fused silica capillary (65 cm total length, 55 cm effective length and 50 µm i.d.) and a microemulsion solution consisted of 1.66% sodium dodecyl sulfate (SDS), 0.91% heptane, 6.61% 1-butanol, and 90.72% borate buffer (20 mM, pH 9.5). Electrophoretic separation was carried out at 20 °C and 20 kV. The samples were injected for 40 s at 20 mbar and detected simultaneously at 205 nm. The electrophoretic parameters indicated that the developed MEEKC-DAD method permitted complete resolution of the analytes within 13 min. The developed method was fully validated according to the FDA guidelines for bioanalytical method validation. The method was linear in the range 200–4000 ng/ml for FTD, FTY, 5CDU, and 100–1000 ng/ml for TIP. The intra/inter-day accuracy and precisions were ≤4% for all drugs. Extraction recovery and stability were also assessed and were within acceptable range. After being validated, the method was applied for the determination of the studied drugs in plasma samples collected from rats injected intraperitoneally with a combination of FTD and TIP. The results obtained were used to study the pharmacokinetics of FTD with its metabolite and TIP in rat plasma.     

LC-ESI-MS/MS法测定人血浆中卢帕他定的浓度（英文）

目的建立测定人血浆中卢帕他定浓度的LC-ESI-MS/MS方法。方法血浆样品加入内标,碱化后用二氯甲烷：乙酸乙酯（20：80）提取,在37℃真空干燥箱中干燥至干,残渣用200μL流动相溶解后进样。色谱条件为：色谱柱为Agilent Eclipse XDB-C18（4.6mm×150mm,5μL）;流动相为乙腈（含1%甲酸）：20mmol·L^-1醋酸铵（76：24,V/V）,流速为0.6mL·min^-1。质谱条件：采用美国安捷仑1100高效液相色谱系统和离子阱（Agilent MSD Trap XCT）检测仪,质谱条件为电喷雾离子源,检测方式为正离子电离、多离子反应监测（MRM）,用于定量分析的离子为卢帕他定m/z416→309,内标氯雷他定m/z383→337。结果该方法应用于检测20名健康志愿者服药后的血浆样品。线性范围为0.05～14ng·mL^-1（r=0.998）,日内和日间精密度均低于15%,方法回收率为85.1%～114.0%。最低检测限为0.05ng·mL^-1（当n=5时,RSD=9.22%）。结论该方法灵敏、准确、快速,可用于该药药代动力学和生物等效性研究。     

Quantitative determination of spinosin in rat plasma by liquid chromatography-tandem mass spectrometry method

A sensitive method for the quantitative determination of spinosin in rat plasma was developed and validated using high-performance liquid chromatographic separation with tandem mass spectrometric detection. The analytes of interest were extracted from rat plasma samples by methyl tert-butyl ether (MTBE) after acidification with 1.0% acetic acid aqueous solution. Chromatographic separation was achieved on an Agilent Zorbax SB-C(18) (50 mm x 4.6 mm, 5 microm) using a isocratic mobile phase consisting of acetonitrile-water (30:70, v/v) with 1% isopropyl alcohol and 0.01% heptafluorobutyric acid. The flow rate was 0.2 ml/min. The column temperature was maintained at 25 degrees C. Detection was performed on a triple quadrupole tandem mass spectrometer by selected reaction monitoring (SRM) mode via electrospray ionization (ESI). The calibration curve was linear over the range of 1.00-400 ng/ml in rat plasma, with 1.00 ng/ml of the lower limit of quantification (LLOQ). The inter- and intra-day precisions and accuracy for all samples were satisfactory. The validated method was successfully applied for the pharmacokinetic study of spinosin in rat. After oral administration of 20mg/kg spinosin to rats, the main pharmacokinetic parameters of T(max), C(max), T(0.5) and AUC(0-T) were 5.33+/-0.58 h, 132.2+/-10.6 ng/ml, 4.89+/-0.37 h, 1.02+/-0.09 microg h/l, respectively.     

Development and validation of a fast and sensitive bioanalytical method for the quantitative determination of glucocorticoids—Quantitative measurement of dexamethasone in rabbit ocular matrices by liquid chromatography tandem mass spectrometry

A sensitive, selective, accurate and robust LC–MS/MS method was developed and validated for the quantitative determination of glucocorticoids in rabbit ocular tissues. Samples were processed by a simple liquid–liquid extraction procedure. Chromatographic separation was performed on Phenomenex reversed phase C18 gemini column (50 mm × 4.6 mm i.d.,) with an isocratic mobile phase composed of 30% of acetonitrile in water containing 0.1% of formic acid, at a flow rate 0.2 mL/min. Dexamethasone (DEX), prednisolone (PD) and hydrocortisone (HD) were detected with proton adducts at m/z 393.20 → 355.30, 361.30 → 147.20 and 363.20 → 121.0 in multiple reaction monitoring (MRM) positive mode respectively. Finally, 50 μL of 0.1% novel DEX mixed micellar formulation was topically administered to a rabbit eye and concentrations were measured. The method was validated over a linear concentration range of 2.7–617.6 ng/mL. Lower limit of quantitation (LLOQ) of DEX and PD was measured in the concentration range of 2.7 and 11.0 ng/mL respectively. The resulting method demonstrated intra and inter-day precision within 13.3% and 11.1% and accuracy within 19.3% and 12.5% for DEX and PD, respectively. Both analytes were found to be stable throughout freeze–thaw cycles and during bench top and postoperative stability studies (r² > 0.999). DEX concentrations in various ocular tissue samples i.e., aqueous humor, cornea, iris ciliary body, sclera and retina choroid were found to be 344.0, 1050.07, 529.6, 103.9 and 48.5 ng/mg protein respectively. Absorption of DEX after topical administration from a novel aqueous mixed micellar formulation achieved therapeutic concentration levels in posterior segment of the rabbit eye.     

Determination of oridonin in rat plasma by reverse-phase high-performance liquid chromatography

A method for quantitative determination of oridonin in rat plasma using reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with UV spectrometry was established and the method was applied to a pharmacokinetics study of oridonin in rats. From a variety of compounds and solvents tested, ticolpidine was selected as the internal standard (IS) and ethyl acetate was found to be the best solvent for extracting oridonin from plasma samples. RP-HPLC analysis of the extracts was performed on an analytical column (DIKMA ODS, 200 mm x 4.6 mm; i.d., 5 microm) equipped with a security guard pre-column system. There was a good linearity over the range 0.05-8.0 microg/mL (r>0.99). The recoveries were about 95.0% in plasma, and the intra- and inter-day coefficients of variation were less than 9.0% in all cases. The limit of detection (LOD) was 0.025 microg/mL and the lower limit of quantification (LLOQ) was 0.05 microg/mL. The RP-HPLC method was readily applied to quantitate oridonin in rat plasma within 24 h in a pharmacokinetics study where experimental rats received a single dose of oridonin (12.5 mg/kg) and the result was presented.     

Development and validation of a method for quantitative determination of valsartan in human plasma by liquid chromatography-tandem mass spectrometry

A sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of valsartan in human plasma was developed and validated. A 0.5 ml aliquot was extracted using solid-phase extraction in an Empore^® high performance extraction disk plate, universal resin 96-well format. The estimated calibration range of the method was 2–2000 ng/ml.

The method was fully validated with intra-day mean accuracy and precision of 94.8–107% and 2.19–5.40% and inter-day mean accuracy and precision of 93.5–105% and 1.87–5.67%, respectively. No significant loss of valsartan in processed samples was confirmed in processed samples for up to 24 h at 10 °C. Sample dilution up to 50-fold with blank human plasma provided acceptable analyses. No interference peaks or matrix effects were observed. No effect of QC sample location results was observed in a 96-well plate. This LC-MS/MS technique was found to improve quantitative determination of valsartan allowing its pharmacokinetic evaluation with clinically relevant doses.     

Aspects of bioanalytical method validation for the quantitative determination of trace elements

Bioanalytical methods are used to quantitatively determine the concentration of drugs, biotransformation products or other specified substances in biological matrices and are often used to provide critical data to pharmacokinetic or bioequivalence studies in support of regulatory submissions. In order to ensure that bioanalytical methods are capable of generating reliable, reproducible data that meet or exceed current regulatory guidance, they are subjected to a rigorous method validation process. At present, regulatory guidance does not necessarily account for nuances specific to trace element determinations. This paper is intended to provide the reader with guidance related to trace element bioanalytical method validation from the authors' perspective for two prevalent and powerful instrumental techniques: inductively coupled plasma-optical emission spectrometry and inductively coupled plasma-MS.