Untitled

Abstract

Organic solvents are integral part of chemical synthesis in pharmaceutical industry. These are commonly used as reaction media, in separation, purification of synthetic products and also for cleaning of equipment. Some of the solvents degrade to other solvents or unknown impurity either during synthesis or in analytical conditions. In this study, we have investigated formation of a trace level impurity, its identification and quantitation by successfully applying the concept of relative response factor (RRF) in GC-HS. The trace level impurity was identified as dimethyl ether (DME), formed due to interaction of strong acid and methanol. Unavailability of its commercial standard made the quantitation in drug substance challenging using gas chromatography. In this work, we have extended the concept of RRF for determination of DME in drug substances. The RRF of DME was established against other process solvents used in method of analysis. Application of RRF in quantitation of DME eliminates the requirement of its external standards during routine analysis at quality control laboratories. INTRODUCTION: In the regulatory environment any unknown peak in chromatography attracts special attention because of increasing focus on safety and efficacy of drug substances and drug products. Presence of an extra or unknown peak in gas chromatographic analysis is not uncommon. These peaks may generally arise either due to thermal degradation of drug substance in chromatographic conditions 1, 2, 3, 4 or may be present in trace level in drug substance itself as solvent or impurity.