Vishal Srivastava

Identification, synthesis and structural characterization of process related and degradation impurities of acrivastine and validation of HPLC method

HIGHLIGHTSFirst reported stability indicating method for the determination of related substances of acrivastine.Separation of geometrical isomer (Imp‐III) in the same method.Identification, synthesis and characterization of new impurities by IR, NMR and LC/ESI–MSn.Forced degradation studies as per ICH guidelines.Method validation data shows that the method is highly sensitive, specific, selective, rugged and robust for the analysis. ABSTRACT Four impurities (Imp‐I–IV) were detected using gradient HPLC method in few laboratory batches of acrivastine in the level of 0.03–0.12% and three impurities (Imp‐I–III) were found to be known and one (Imp‐IV) was unknown. In forced degradation study, the drug is degraded into four degradation products under oxidation and photolytic conditions. Two impurities (Imp‐III and ‐IV) were concurred with process related impurities whereas Imp‐V and ‐VI were identified as new degradation impurities. Based on LC‐ESI/MSn study, the chemical structures of new impurities were presumed as 1‐[(2E)‐3‐(4‐methylphenyl)‐3‐{6‐[(1E)‐3‐oxobut‐1‐en‐1‐yl]pyridin‐2‐yl}prop‐2‐en‐1‐yl]pyrrolidin‐1‐ium‐1‐olate (Imp‐IV), 1‐{[3‐(4‐methylphenyl)‐3‐{6‐[(1E)‐3‐oxobut‐1‐en‐1‐yl]pyridin‐2‐yl}oxiran‐2‐yl]methyl}pyrrolidin‐1‐ium‐1‐olate (Imp‐V) and 2‐[2‐(4‐methylphenyl)‐3‐[(1‐oxidopyrrolidin‐1‐ium‐1‐yl)methyl]oxiran‐2‐yl]‐6‐[(1E)‐3‐oxobut‐1‐en‐1‐yl]pyridin‐1‐ium‐1‐olate (Imp‐VI), and confirmed by their synthesis followed by spectroscopic analysis, IR, NMR (1H, 13C) and mass. An efficient and selective high‐performance liquid chromatography method has been developed and resolved well the drug related substances on a Phenomenex Gemini C‐18 (250 × 4.6 mm, particle size 5 &mgr;m) column. The mobile phase was composed of sodium dihydrogen phosphate (10 mM) and methanol, temperature at 25 °C, and a PDA detector set at 254 nm used for detection. The method was validated with respect to specificity, linearity, precision, accuracy, and sensitivity and satisfactory results were achieved. Identification, synthesis, characterization of impurities and method validation were first reported in this paper.

Development of a 30 W (peak) S-band Helix Travelling-wave Tube

The development of a 30 W (peak) S-band helix travelling-wave tube (TWT) for use as a preamplifier in a radar system is described. The salient features of the design include a gridded Pierce electron gun, a slow-wave structure consisting of a wire helix supported by three alumina rods in a metal shell, an isolated collector, and complete ceramic-metal structure of tube envelope.