The influence of the liner type on the GC injection: a specific look at PFAS and other POPs

Introduction Nowadays, liquid chromatography is the most widely used technique for analyzing per- and polyfluoroalkyl substances (PFAS). With the discovery of volatile and semi-volatile PFAS, also gas chromatography (GC) is gaining space for the analysis of these pollutants from different matrices. Generally, gas chromatography is the main technique used for the analysis of (semi-)volatile compounds. Despite its widespread use, the choice of liner is often not given much consideration when optimizing the method. However, in hot vaporization injections (e.g., split and splitless), the mechanism of analyte introduction into the injector and transfer into the column is rather complex, and if not properly optimized, can generate severe discrimination in quantitative analysis. The liner is designed to slow down the passage of the liquid sample between the syringe needle outlet and the column inlet in hot vaporization injections, allowing for more complete and uniform evaporation of the sample and that is why it is important to choose the one best suited to the analysis that need to be performed. There are many types of liners with different characteristics (e.g., presence of packing, different geometries, presence of restrictions), which means that the vaporization of analytes is not always the same. Materials and Methods In this study, the influence of liners with different geometries on injector discrimination phenomena in vaporization injections was evaluated. Specifically, they differed each other by the presence or not of glass wool and its position, the presence or not of focus points that hold the glass wool in the right position, the use of a different packing material than glass wool (i.e., felt) or a different geometry (i.e., cycle), the presence or absence restrictions at the ends of the liner. Results These liners were compared in terms of recovery, discrimination among compounds with different volatilities, reproducibility of the vaporization and stability. The parameters were evaluated for different PFAS families (e.g., fluorotelomer alcohols, fluorotelomer acrylates, fluorotelomer iodine) and other POPS (PCBs, PAHs, Pesticides) using GC-FID and GC-MS. Discussion and Conclusion This study shows that the liner has an impact on the resulting GC method in terms of discrimination, preservation, and the column transfer of the analytes.