MATRIX EFFECTS AND SOLUTE DISCRIMINATION WHEN INJECTING DIRTY SAMPLES IN CAPILLARY COLUMNS - COMPARATIVE-STUDY BETWEEN CLASSICAL SPLIT AND SPLITLESS INJECTIONS

Vaporization inside the injector chamber is a very complex process. The presence of non-volatile material may change the volatilization rate of a large number of species. In particular, splitting is far from ideal, as significant differences were observed in the splitting of clean and dirty samples and no discrimination-free chromatographic conditions could be found. The pattern of discrimination was strongly dependent on the glass liner geometry. When the non-volatile content of the sample was increased and packed inserts were used, smaller amounts of the most volatile compounds entered the column, whereas the least volatile compounds seemed not to be affected. The opposite effect was found when using empty injector inserts. Splitless injection was less affected by the presence of non-volatile components in the sample when the distance between the needle and the column entrance was large enough. Incomplete evaporation only occurred with very dirty samples, and this effect was avoided by increasing the injector temperature.