Residual solvents are used in the manufacture of active pharmaceutical ingredients (APIs), excipients, or in preparation of drug products, and are not removed during the purification processes. Residual solvents are one of the three main impurities in pharmaceutical materials; the other two are organic and inorganic impurities. Residual solvents do not provide any therapeutic benefit and should be removed to the extent possible, fulfilling quality-based requirements as per International Conference on Harmonization (ICH) guidelines – this is one of the standards to control the quality and the purity of the pharmaceutical substances, excipients, or drug products.
This paper will demonstrate the analysis of all three classes of residual solvents by pressure-balanced headspace sample introduction and GC-FID analysis. In addition to a discussion of the instrumental technique, the choice of the diluent will also be studied; two diluents will be used throughout.