Large-volume on-column injections for gas chromatography.

Large‐volume injection is an attractive means to improve detection limits when analyzing dilute sample extracts. There is now no need to achieve enrichment by means of solvent evaporation, which makes the total analytical procedure less reliable and less robust due to loss of volatile compounds. In this study on‐column injection was applied for large‐volume injection using an on‐column injector in combination with a deactivated uncoated fused silica capillary (retention gap) and an early solvent vapor exit. Two strategies are described. The first one relies on the programmable speed of an infusion pump, which is adapted such that it lies just above the evaporation rate of the extraction solvent used. With the second procedure, which can be used for a commercially available autosampler, the evaporation speed is adjusted to the fixed speed of injection by varying the temperature during injection. During optimization the additional solvent evaporation time was determined. The optimum conditions for an injection volume of 100 μL of either n‐hexane or ethyl acetate are reported. Large‐volume injection was used for simplified and miniaturized solid‐phase extraction procedures. The procedures were used to determine various organic micropollutants, such as organophosphorus pesticides and triazine herbicides, in tap and surface water extracts, using a flame photometric, and a mass spectrometric detector. For both methods good recovery for most of the analytes (70–87%), linear calibration curves (0.01‐5 μg/L range), and relative standard deviations of less than 10% were obtained. Detection limits typically were in the range of 1–10 ng/L for GC‐FPD and 10–150 ng/L for GC‐MS. When working in the time‐scheduled multiple ion detection mode detection limits in GC‐MS were one order of magnitude lower. © 1995 John Wiley & Sons, Inc. Copyright © 1995 John Wiley & Sons, Inc.