To detect sub-ppb levels of the antibiotic chloramphenicol in honey matrix, a convenient method of extraction and measurement using liquid chromatography with detection by tandem mass spectrometry (LC/MS/MS) was developed. Honey samples fortified with chloramphenicol and isotopically labeled chloramphenicol were extracted using diatomaceous-based supported liquid-liquid extraction cartridges to generate a standard calibration curve. Four MS/MS transitions were used for quantification and four other transitions for confirmation of chloramphenicol. The limit of detection for chloramphenicol was 0.05 ng/g and the lower limit of quantification was 0.1 ng/g. Several commercial honey samples were analyzed for chloramphenicol content using this method.
A bioanalytical method was developed and validated using High Performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) technique for the determination of Rivaroxaban in human plasma. The samples were extracted using solid-phase extraction (SPE) technique wherein Rivaroxaban D4 has been used as the internal standard. The use of isocratic Liquid chromatography (LC) method has enabled to achieve 2.0 minutes along with their respective internal standard using a Phenomenex Gemini C18, 50*4.6mm, 5µ column. The developed method was specific and sensitive having no interfering peaks in the drug free plasma. The method was validated for a linear range of 2.00-500.93 ng/mL for Rivaroxaban with a correlation coefficient e" 0.99. The limit of detection (LOD) of 2 ng/mL for Rivaroxaban a signal-to noise (S/N) >10 was achieved, Electrospray ionization source in positive mode was used for the detections of Rivaroxaban and IS. Precursor to product ion transition of m/z 436.20 > 144.80 for rivaroxaban and m/z 440.20 > 144.70 for IS were used in multiple reaction monitoring mode. Intra-run precision (%CV) ranged from 3.8% to 0.9% for Rivaroxaban. Inter-run accuracy(%Bias) ranged from -3.1% to -1.9% for Rivaroxaban .The overall recoveries for Rivaroxaban, Rivaroxaban D4 were found to be >96%. Rivaroxaban was found to be stable at various temperatures and for about 5 freeze-thaw cycles and reconstituted samples were stable up to 72 hours post to extraction. The developed and validated method was found to be precise, reproducible and a high throughput of analyzing more than 400 samples per day could be achieved with a shorter run time of 2.0 minutes. The developed method is useful to measuring Rivaroxaban plasmatic concentrations in pharmacokinetics studies and in therapeutic drug monitoring.
A strategy is developed for the identification of isocephalomannine in the presence of alkali metal ion adducts and other cephalomannine isomers in a paclitaxel active pharmaceutical ingredient. Intact molecular ion analyses and a sub-structural study have been performed for the differentiation of isocephalomannine (2-debenzoylpaclitaxel-2-pentenoate) from cephalomannine and 7-epi-cephalomannine. A comparative study of the cephalomannine isomers was carried out using molecular ions (MS) and fragmentation patterns (MS/MS) for sub-structural analysis. An attempt has been made to identify isocephalomannine in Cremophor(R) EL formulations.
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