Determination of clindamycin in animal plasma by high-performance liquid chromatography combined with electrospray ionization mass spectrometry

A method for the quantification of clindamycin in animal plasma using high-performance liquid chromatography combined with electrospray ionization mass spectrometry (LC/ESI-MS/MS) is presented. Lincomycin is used as the internal standard. The sample preparation includes a simple deproteinization step with trichloroacetic acid. Chromatographic separation is achieved on an RP-18 Hypersil column using gradient elution with 0.01 M ammonium acetate and acetonitrile as mobile phase. Good linearity was observed in the range 0-10 microg ml(-1). The limit of quantification of the method is 50 ng ml(-1) and the limit of detection is 1.3 ng ml(-1). The method was shown out to be of use for pharmacokinetic studies of clindamycin formulations in dogs.     

Optimization of a nitrogen analyser based on the Dumas method

The objectives of this work was to obtain a total nitrogen concentration in milk with the Dumas method for industrial and research applications. This method was faster than the Kjheldal method (5 min against 2 h or 3 h) but less precise. A three factor experimental design was performed to optimize the instrument, a FP-2000 supplied by LECO. The first interpretation of the experimental design was disappointing and no conclusion could be done. It was not a failure of experimental design but a lack of thinking on the physical and chemical aspect of the problem. Selection and construction of composite responses based on chemical and physical consideration were the keys to optimize the Dumas method. This method is now as precise as the Kjheldal method, but considerably faster.     

Hydride generation atomic fluorescence spectrometric determination of As, Bi, Sb, Se(IV) and Te(IV) in aqua regia extracts from atmospheric particulate matter using multivariate optimization

A highly sensitive and simple method, based on hydride generation and atomic fluorescence detection, has been developed for the determination of As, Bi, Sb, Se(IV) and Te(IV) in aqua regia extracts from atmospheric particulate matter samples. Atmospheric particulates matter was collected on glass fiber filters using a medium volume sampler (PM1 particulate matter). Two-level factorial designs have been used to optimise the hydride generation atomic fluorescence spectrometry (HG-AFS) procedure. The effects of several parameters affecting the hydride generation efficiency (hydrochloric acid, sodium tetrahydroborate and potassium iodide concentrations and flow rates) have been evaluated using a Plackett-Burman experimental design. In addition, parameters affecting the hydride measurement (delay, analysis and memory times) have been also investigated. The significant parameters obtained (sodium tetrahydroborate concentration, sodium tetrahydroborate flow rate and analysis time for As; hydrochloric acid concentration and sodium tetrahydroborate flow rate for Se(IV); and sodium tetrahydroborate concentration and sodium tetrahydroborate flow rate for Te(IV)) have been optimized by using 2ⁿ + star central composite design. Hydrochloric acid concentration and sodium tetrahydroborate flow rate were the significant parameters obtained for Sb and Bi determination, respectively. Using a univariate approach these parameters were optimized. The accuracy of methods have been verified by using several certified reference materials: SRM 1648 (urban particulate matter) and SRM 1649a (urban dust). Detection limits in the range of 6 × 10⁻³ to 0.2 ng m⁻³ have been achieved. The developed methods were applied to several atmospheric particulate matter samples corresponding to A Coruña city (NW Spain).     

Development and validation of a sensitive LC-MS/MS method with electrospray ionization using multiple ions for quantitation of torcetrapib in hamster and dog plasma

A highly sensitive and specific LC-MS/MS method has been developed and validated for the estimation of torcetrapib (TTB) with 100 microL hamster/dog plasma using DRL-16126 as an internal standard (IS). The API-4000 Q Trap LC-MS/MS was operated under multiple-reaction monitoring mode using the electrospray ionization technique. The assay procedure involved extraction of TTB and IS from plasma with acetonitrile, which yielded consistent recoveries of 65.73 and 94.01% for TTB and 79.68 and 90.70% for IS in hamster and dog plasma, respectively. The total chromatographic run time was 3.0 min and the elution of TTB and IS occurred at approximately 2.25 and 2.20 min, respectively. The resolution of peaks was achieved with 0.01 m ammonium acetate:acetonitrile (15:85, v/v) at a flow rate of 0.40 mL/min on an Inertsil ODS-3 column. The method was proved to be accurate and precise at linearity range of 1.00-200 ng/mL with a correlation coefficient (r) of > or = 0.993. The method was rugged with 1.00 ng/mL as the lower limit of quantitation. TTB was stable in the battery of stability studies. The application of the assay to preclinical pharmacokinetic studies confirmed the utility of the assay to derive hamster/dog pharmacokinetic parameters.     

Tutorial review on validation of liquid chromatography–mass spectrometry methods: Part II

This is the part II of a tutorial review intending to give an overview of the state of the art of method validation in liquid chromatography mass spectrometry (LC–MS) and discuss specific issues that arise with MS (and MS–MS) detection in LC (as opposed to the “conventional” detectors). The Part II starts with briefly introducing the main quantitation methods and then addresses the performance related to quantification: linearity of signal, sensitivity, precision, trueness, accuracy, stability and measurement uncertainty. The last section is devoted to practical considerations in validation. With every performance characteristic its essence and terminology are addressed, the current status of treating it is reviewed and recommendations are given, how to handle it, specifically in the case of LC–MS methods.     

婴儿湿巾缓冲能力的测试——一个贴近生活的实验

为了有效提升学生在缓冲溶液学习过程中的学习兴趣及积极性,在此推荐一个将现实中的生活用品作为实验对象引入实验课教学过程中的案例。该实验设计将性质实验扩充到婴儿湿巾,将实验内容变为对婴儿湿巾工作原理的验证,而不再是过去简单的酸碱体系的配制及相关验证实验。通过该实验的实施,学生普遍反映能够有效激发其在学习缓冲溶液相关课程中的学习积极性与兴趣,并最终促使学生认知缓冲体系内pH变化的特点及缓冲机理。     

Conventional and ultrasound-assisted methods for extraction of bioactive compounds from red araçá peel (Psidium cattleianum Sabine)

The present study aimed to maximize the conventional extraction and compare it with the ultrasound-assisted method for extracting bioactive compounds obtained from the red araçá peel. The behavior of anthocyanins related to the pre-treatment of the vegetal matrix, employed solvent, extraction kinetics of both methods, the levels of total phenolic compounds, flavonoids and carotenoids, as well as the antioxidant activity were evaluated. The ultrasound-assisted extraction (40 KHz −154 W and 90 min) had an increase of 12% in the levels of anthocyanins (121.85 Eq. mg of cyanidin-3-glycoside/100 g of peel) and a 25% reduction in time extraction compared to conventional extraction by maceration (116.81 Eq. mg of cyanidin-3-glycoside/100 g of peel) using 90% ethanol, for 2 h, pH 1.5, at 40 °C and mass/volume ratio 1 g/10 mL). Analyses of the total phenolic compounds, flavonoids and carotenoids presented promising results for the ultrasound-assisted and conventional extractions, respectively. Analyzes of total phenolic compounds, flavonoids and carotenoids, show promising results for ultrasound-assisted extractions, respectively, indicating that red araçá is rich in bioactive compounds beneficial to human health, in addition to being considered natural pigments that can be used in food.     

应用超高效液相色谱-四极杆-飞行时间质谱建立茶叶中农药残留的筛查与确证方法

基于超高效液相色谱-四极杆-飞行时间质谱(UPLC-QTOF-MS),使用UNIFI软件建立91种农药残留的筛查与确证方法,进行定性方法验证并应用于流通市场中茶叶的筛查检测。通过对收集的农药认证标准物质(CRM)分析,构建91种农药化合物的质谱数据库。样品经乙腈提取,固相萃取柱净化,Acquity BEH C18色谱柱分离,在MS^E模式下进行全信息采集(ESI+), UNIFI软件对数据进行匹配分析。设置保留时间最大偏差为±0.1 min,精确质量偏差阈值为±5×10^-6,可识别加合物形式包括[M+H]⁺、[M+Na]⁺、[M+K]⁺、[M+NH₄]⁺。参照SANTE/11813/2017指南进行定性方法学验证。在21份茶叶样品中添加混合标准溶液至4个水平(0.01、0.05、0.10、0.20 mg/kg),确定每种农药在茶叶样品中的筛查检出限(SDL),共评估了1 911种农药/样品组合。发现有66种农药的SDL为0.01 mg/...     

Stability-indicating RP-HPLC method development and validation for determination of nine impurities in apixaban tablet dosage forms. Robustness study by quality by design approach

A quality by design (QbD) based high-resolution HPLC method is described for determination of impurities in apixaban (APX) in the tablet dosage form. Employing a simple and stability-indicating HPLC method, nine known impurities were quantified with good peak resolution. Mobile phase A (MP-A) was prepared with buffer and acetonitrile 90:10 v/v, while mobile phase B (MP-B) contained water and acetonitrile 10:90 v/v. The gradient program was 0 min, MP-A 75%, B 25%; 20 min, MP-A 65%, B 35%; 30 min, MP-A 40%, B 60%; 40min, MP-A 40%, B 60%; 42 min, MP-A 75%, B 25%; and 50 min, MP-A 75%, B 25%. The chromatographic separation was achieved using a Zorbax RX C₁₈ 250 × 4.6 mm column, 5 μm (1.0 ml min⁻¹, 280 nm, 50 μl) and a column temperature of 40°C. Several separation studies were carried out using design of experiments to optimize the method. Validation results confirm the applicability of the developed method for quality analysis and stability studies of the regular product on the manufacturing stream.     

Validated LC–MS/MS method for quantitation of a selective JAK1 inhibitor,filgotinib in rat plasma,and its application to a pharmacokinetic study in rats

Filgotinib is a selective JAK1 (Janus kinase) inhibitor, filed in Japan for the treatment of rheumatoid arthritis. In this paper, we report a validated liquid chromatography coupled with tandem mass spectrometry for the quantification of filgotinib in rat plasma using tofacitinib as an internal standard (IS) as per the Food and Drug Administration regulatory guidelines. Filgotinib and the IS were extracted from rat plasma using ethyl acetate as an extraction solvent and chromatographed using an isocratic mobile phase (0.2% formic acid:acetonitrile; 20:80, v/v) at a flow rate of 0.9 mL/min on a Gemini C₁₈ column. Filgotinib and the IS were eluted at ~1.31 and 0.89 min, respectively. The MS/MS ion transitions monitored were m/z 426.3 → 291.3 and m/z 313.2 → 149.2 for filgotinib and the IS, respectively. The calibration range was 0.78–1924 ng/mL. No matrix effect and carryover were observed. Intra- and inter-day accuracies and precisions were within the acceptance range. Filgotinib was stable for three freeze–thaw cycles: on bench-top up to 6 h, in an autosampler up to 21 h, and at −80 ° C for 1 month. This novel method has been applied to a pharmacokinetic study in rats.