A Review: Residual Solvents and Various Effective Gas Chromatographic Techniques in the Analysis of Residual Solvent
Residual solvents are the undesired substances (solvents) used or produced during the manufacture of a excipients, drug or pharmaceutical formulation and are not completely removed by practical methods in the final finished product. These solvents can be toxic in nature. Therefore, analysis of residual solvents becomes a necessary tool for the quality control of pharmaceuticals. The acceptable limits for these substances are given in ICH guidelines (Guideline for Residual solvents, Q3C). The intension of this paper is to review toxic limit of residual solvents and to discuss various Gas Chromatographic (GC) techniques to analyze about all the residual solvents mentioned in ICH guideline, Q3C. Gas Chromatography is coupled with various other techniques to increase the sensitivity of the method. Various techniques included in this study are; gas chromatography, direct injection method, headspace gas chromatography(HSGC), static headspace sampling, dynamic headspace sampling, fast gas chromatography, headspace gas chromatography coupled flame ionisation detector (HSGC-FID), head space gas chromatography- mass spectrometry (HSGC-MS), flow- modulation technique for gas chromatography, thermal desorption- headspace gas chromatography (TD-HSGC), headspace gas chromatography- solid phase microextraction (HSGC-SPME), dual column gas chromatography, multiple headspace- single drop microextraction (MHS-SDME) and headspace gas chromatography- solid phase microextraction- mass spectrometry (HSGC-SPME-MS). Application of various gas chromatographic techniques to some drugs or pharmaceutical preparations are also covered under the study.