Authors:Ch. B. V. N. Raju, H. K. Sharma, Ch. S. Rao, and G. N. Rao
Linear gradient HPLC on a C8 column has been used for separation of individual related substances of amoxicillin listed in the European Pharmacopoeia and a newly identified degradation impurity. The USP plate count for the amoxicillin peak was more than 3000 and USP tailing for the same peak was less than 2.0. Forced degradation studies were conducted on amoxicillin drug substance using ICH stress study guidelines to demonstrate the specificity and stability-indicating nature of the method. A new impurity observed after thermal and alkaline degradation was identified as N-pivaloylamoxicillin. The LOD and LOQ for individual related substances were below 0.045 and 0.086% (w/w), respectively. The method was fully validated in accordance with ICH analytical method validation guidelines. The results of the study prove the method is specific, precise, linear, robust, and can be used for evaluation of the stability of amoxicillin drug substance.
Authors:A. B. A. Ahmed, A. S. Rao, M. V. Rao, and R. M. Taha
Gymnemic acid (GA), a well known anti-diabetic compound has been detected in methanol extracts of intact leaves and in vitro callus cultures derived from leaf explants of Gymnema sylvestre. Callus biomass was developed in MS medium with optimum plant growth regulators (OPGRs) of 2,4-D (1.5 mg L−1) + KN (0.5 mg L−1) under abiotic stress conditions at 45 days determined by growth curve analysis. GA detection and quantification were carried out using thin-layer chromatography (TLC), highperformance thin-layer chromatography (HPTLC), high-performance liquid chromatography (HPLC), and gravimetric techniques. GA detection peak area and their absorption spectra were evaluated through HPTLC and HPLC with the standard GA. Quantification of GA had showed the linearity, accuracy, robustness and precision by HPLC. GA content was significantly higher in gravimetric method than HPLC. All these methods were found to be simple, accurate, selective and rapid and could be successfully applied for the determination of GA. It could have potential as a pharmaceutical drug for Type 1 diabetes mellitus (IDDM) and obesity.
A novel, rapid, and sensitive liquid chromatography-tandem mass spectrometric method was developed and validated for the simultaneous quantification of tenofovir, emtricitabine, and efavirenz in human plasma. Nevirapine was used as an internal standard. The analytes and the internal standard were extracted from human plasma sample by solid-phase extraction technique (SPE). The reconstituted samples were chromatographed on a Chromolith ROD C18 column (50 × 4.6 mm; 5 μ) by gradient elution using a mixture of ammonium acetate buffer (5 mM) and 0.1% formic acid in acetonitrile as the mobile phase at a flow rate of 1.0 mL min−1. The calibration curve obtained was linear (r2 ≥ 0.9990) over the concentration range of 2.5–650 ng mL−1 for tenofovir and 10–4000 ng mL−1 for emtricitabine and efavirenz. The results of the intra- and inter-day precision and accuracy studies were well within the acceptable limits. A run time of 2.5 min for each sample made it possible to analyze more than 300 plasma samples per day. The proposed method was found to be applicable to clinical studies, and the authenticity in the measurement of clinical data is demonstrated through incurred samples reanalysis (ISR).