Extending the applicability of gas chromatography in pharmaceutical analysis
Gas chromatography (GC) is a well-established separation technique based on the selective interaction of the analytes in the gas phase (and moving by the mobile phase) with the stationary phase. As analytes should be easily volatilised, its use is somehow limited, often requiring long pre-treatments. In this work, the use of less conventional headspace (HS) modes such as multiple headspace (MHE), total volatilization (TVT) and full evaporation (FET) are explored to overcome current challenges in pharmaceutical analysis. Moreover, an experimental design was used for the optimization of pre-treatments, extending the applicability of this technique.
First, an MHE-GC method for the characterisation of sorption capacities of solids has been developed, from its theoretical background to its application to the classification of different mesoporous silica materials used for drug delivery. Then, the overestimation risk in the analysis of methylsiloxanes was overcome by the development of a TVT-GC method, that can be combined with a single step liquid extraction to be applied to different complex matrices. Similarly, the sample consumption was diminished by optimisation of the pre-treating derivatisation reactions, enabling quality control of mixed triglycerides used for clinical diagnosis. Finally, the use of FET-GC for water determination in pharmaceutical products has been discussed as sample-saving alternative to conventional methods, without the risk of atmospheric moisture contamination.