In-vial liquid-liquid extraction with subsequent large-volume on-column injection into GC-MS for the determination of anilines in tap, surface, and wastewater

In this study miniaturized liquid-liquid extraction carried out in an autosampler vial was used to determine a series of anilines in tap, surface, and industrial wastewater. The analytes were extracted from the aqueous phase into n-hexane and 100 mu l Of the extract, i.e., 10-20%, was injected into the gas chromatography (GC) system using an on-column injector in combination with a deactivated uncoated fused silica capillary (retention gap) and an early solvent vapor exit. A mass spectrometer was used for detection and identification. The parameters for large-volume injection, i.e., the evaporation rate, speed of injection, and injection temperature, were optimized using accurate measurement of the actual flow rate of the carrier gas into the GC system. This measurement was used as input for a solvent vapor-exit controller, which was equipped with a microprocessor for determination of the endpoint of the evaporation process. The optimum conditions for an injection volume of 100 mu L of n-hexane are reported. Extraction with a water-to-n-hexane-ratio (1:1, v/v) gave quantitative recoveries except for aniline (46%). The addition of sodium chloride improved the extraction yield for aniline about 10%. Linear calibration curves were obtained in the 0.01-1-mu g/L concentration range, relative standard deviations were less than 10%, and detection limits typically were 4-20 ng/L for GC-mass spectrometry in the multiple-ion-detection mode. The total procedure allowed the analysis of unfiltered water samples; that is, no sample treatment was necessary. (C) 1998 John Wiley & Sons, Inc.