We are interested in addressing various analytical challenges that are currently facing the pharmaceutical industry. Most recently, we have collaborated extensively with Genentech to develop contemporary and practical analytical methods to quantify genotoxic impurities (GTIs) at trace-level concentrations. GTIs are compounds that can induce genetic mutations, chromosomal breaks, and/or chromosomal rearrangements in humans. Additionally, these compounds can also exhibit potential carcinogenic activity. The United States Food and Drug Administration (FDA) and the European Medicines Agency (EMA) have imposed stringent regulations on the amount of GTIs present in pharmaceuticals. Depending on the dose and duration of exposure, the allowable daily intake (ADI) can be as low as 1.5 μg/day, which in perspective, would be translated to low parts-per-million (ppm) or sub-ppm concentration ranges of GTIs in drug substances. This highly conservative threshold also applies to pharmaceutical impurities containing structurally alerting functional groups that may possess genotoxic activity. Although GTIs that enter human body may come from drug substances, excipients, degradants, or metabolites, the major source of GTIs is usually active pharmaceutical ingredient (API) manufacturing, which may require the use of genotoxic reagents, solvents, and catalysts. Thus, monitoring the presence of various GTIs in drug substances is of great importance for the pharmaceutical industry.
In a recent collaboration with Genentech, we applied a number of thermally-stable ILs as diluents in the trace-level analysis of two classes of GTIs, namely, alkyl/aryl halides and nitroaromatic compounds, by static headspace gas chromatography coupled to electron capture detection (SHS-GC/ECD). This approach greatly broadens the applicability of SHS-GC for the determination of high boiling GTIs (≥ 130°C) and provides up to a 4000-fold improvement in limits of detection compared to traditional SHS-GC diluents. Optimization of the incubation temperature (up to 210 °C) resulted in varying response for alkyl/aryl halides and enhanced response for nitroaromatic compounds. Excellent recoveries of all GTIs at low ppm-levels were obtained from real APIs.