A simple, rapid, precise and accurate High-Performance Thin Layer Chromatography (HPTLC) method was developed and validated for the estimation of Nintedanib, a novel tyrosine kinase inhibitor used in idiopathic pulmonary fibrosis, in bulk drug. Chromatography was carried out using silica gel 60 F254 Thin Layer Chromatography (TLC) plate and mobile phase Chloroform: Methanol in the ratio 7:3 v/v. The densitometric determination was done at 386 nm. Regression analysis data for the calibration plot were indicative of a good linear relationship between response and concentration over the range of 800–3200 ng/band. The variance (r) was found to be 0.999. The Limit of Detection (LOD) and Limit of Quantitation (LOQ) were found to be 83.357 ng/band and 252.599 ng/band respectively. The method was validated according to the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use [ICH Q2(R1)] guideline. The method was precise and accurate with %RSD 0.5323 (intraday) and 0.6939 (interday) respectively and percentage recoveries in the range 99.65–101.43%.
A highly sensitive, accurate and robust LC-MS/MS method was developed and validated for determination of nimorazole (NMZ) in rat plasma using metronidazole (MNZ) as internal standard (IS). The analyte and IS were extracted from plasma by precipitating protein with acetonitrile and were chromatographed using an Agilent Poroshell 120, EC-C18 column. The mobile phase was composed of a mixture of acetonitrile and 0.1 % formic acid (85:15 v/v). The total run time was 1.5 min and injection volume was 5 μL. Multiple reaction monitoring mode using the transitions of m/z 227.1 → m/z 114.0 for MNZ and m/z 172.10 → m/z 128.1 for IS were monitored on a triple quadrupole mass spectrometer, operating in positive ion mode. The calibration curve was linear in the range of 0.25-200 ng/mL (r(2) > 0.9996) and the lower limit of quantification was 0.25 ng/mL in the rat plasma samples. Recoveries of NMZ ranged between 88.05 and 95.25%. The precision (intra-day and inter-day) and accuracy of the quality control samples were 1.25-8.20% and -2.50-3.10, respectively. The analyte and IS were found to be stable during all sample storage and analysis procedures. The LC-MS/MS method described here was validated and successfully applied to pharmacokinetic study in rats.
A sensitive, reliable, and reproducible headspace gas chromatography-flame ionization detection method was developed and validated to detect and quantify low levels of tert-butyl nitrite (TBN). TBN is a reagent commonly used by synthetic chemists for nitrogen insertion reactions and is also a potential mutagenic impurity due to a structurally alerting nitrite group. However, there is an inherent analytical challenge in the quantification of TBN due to its chemical instability in solution (e.g., degradation of TBN to tert-butyl alcohol, TBA, in protic solvents). The proposed methodology is based on stabilizing TBN in solution by adding imidazole to a sample diluent before static headspace gas chromatographic analysis. The gas chromatography method utilizes a high-polarity poly(ethylene glycol) stationary phase that provides the resolution of TBN from an interference peak in the sample matrix and facilitates the attainment of the required sensitivity of the TBN peak. The limit of detection (LOD) and limit of quantitation (LOQ) of this method were established as 0.05 μg mL −1 (0.05 ppm) and 0.15 μg mL −1 (0.15 ppm), respectively. Method validation experiments indicated excellent analytical performance of the method with respect to specificity (resolution of ∼2.2 from a matrix interference peak), linearity (range: 16.7−1000% of the working concentration), precision (relative standard deviation, RSD, of 1.0% for n = 6 at LOQ level), and recovery (94% at LOQ level). This is the first report of a practical strategy to stabilize TBN for its trace-level quantification.
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