PROGRAMMED-TEMPERATURE INJECTOR FOR LARGE-VOLUME SAMPLE INTRODUCTION IN CAPILLARY GAS-CHROMATOGRAPHY AND FOR LIQUID-CHROMATOGRAPHY GAS-CHROMATOGRAPHY INTERFACING

The introduction of large sample volumes in capillary gas chromatography is becoming increasingly important in various application areas. Especially in the analysis of very dilute samples (e.g., environmental samples) and in coupled LC-GC, large volume sampling is extremely important. Programmed-temperature sample introduction is shown to be an attractive technique for these purposes. In this paper we present some applications of large volume sampling in environmental analysis. Water samples were analyzed using both off-line and on-line extraction with gas chromatography (GC) analysis. In the off-line method, pollutants were extracted into hexane or methylene chloride. Using the programmed-temperature injector, up to 250-mu-L of the extract could be introduced into the GC system. In this way, reproducible quantitative analyses of PAHs and herbicides were achieved at sub-ppb concentrations using flame ionization detection. In the on-line mode, pollutants were preconcentrated on a short liquid chromatography (LC) column packed with a PLRP-S solid phase extraction material. After the trapping step, the components were desorbed by ethyl acetate and transferred directly into the programmed-temperature vaporizer (PTV-GC system. Using this method, detection limits below about 1 ppb of herbicides in water were obtained.