Gas chromatography (GC) is the main technique used for the qualitative and quantitative analysis of (semi-)volatile compounds. Although it is a widely used technique, there are aspects that are not always considered, but which are crucial in method optimization. In the case of quantitative analyses, two factors that must be taken into consideration are the injector and detector discriminations. Concerning the first type of discrimination, it generally occurs in hot vaporization injections. In this type of injections, 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. An important component to choose when performing split and splitless analyses is the liner. This insert is designed to slow down the passage of the liquid sample between the syringe needle outlet and the column inlet, allowing for more complete and uniform evaporation of the sample [2]. There are many types of liners with different characteristics (e.g., presence of packing, different geometries, presence of restrictions), and the choice is important to reduce injector discrimination. In this study, the influence of liners with different geometries on injector discrimination phenomena in vaporization injections was evaluated. Specifically, five liners with different characteristics designed for split injections and six liners for splitless injections were evaluated. A standard solution containing 35 compounds with different chemical structures (linear alkanes, branched alkanes, cycloalkanes, alkenes, aromatics, N/O-containing compounds) was analyzed in GC-FID to evaluate recovery, discrimination among compounds with different volatilities, reproducibility and efficiency of the vaporization. For split mode liners, different split ratios were also evaluated. To calculate recoveries, it was necessary to eliminate discrimination at the detector. This parameter was calculated by normalizing the results of each analysis with those obtaining from on-column analyses performed considering the same mass entering the column.
The impact of liner geometry on the vaporization process in GC injection
Flavio Antonio Franchina;Cristina Meo;Allan Polidoro;Monica Romagnoli
2026
Abstract
Gas chromatography (GC) is the main technique used for the qualitative and quantitative analysis of (semi-)volatile compounds. Although it is a widely used technique, there are aspects that are not always considered, but which are crucial in method optimization. In the case of quantitative analyses, two factors that must be taken into consideration are the injector and detector discriminations. Concerning the first type of discrimination, it generally occurs in hot vaporization injections. In this type of injections, 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. An important component to choose when performing split and splitless analyses is the liner. This insert is designed to slow down the passage of the liquid sample between the syringe needle outlet and the column inlet, allowing for more complete and uniform evaporation of the sample [2]. There are many types of liners with different characteristics (e.g., presence of packing, different geometries, presence of restrictions), and the choice is important to reduce injector discrimination. In this study, the influence of liners with different geometries on injector discrimination phenomena in vaporization injections was evaluated. Specifically, five liners with different characteristics designed for split injections and six liners for splitless injections were evaluated. A standard solution containing 35 compounds with different chemical structures (linear alkanes, branched alkanes, cycloalkanes, alkenes, aromatics, N/O-containing compounds) was analyzed in GC-FID to evaluate recovery, discrimination among compounds with different volatilities, reproducibility and efficiency of the vaporization. For split mode liners, different split ratios were also evaluated. To calculate recoveries, it was necessary to eliminate discrimination at the detector. This parameter was calculated by normalizing the results of each analysis with those obtaining from on-column analyses performed considering the same mass entering the column.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
