LARGE-VOLUME INJECTIONS IN GAS-CHROMATOGRAPHY ATOMIC-EMISSION DETECTION - AN APPROACH FOR TRACE-LEVEL DETECTION IN WATER ANALYSIS

The ruggedness and analytical performance of on-line capillary gas chr omatography-atomic emission detection (GC-AED) have been studied using 100-mu l injections of sample solutions in ethyl acetate, via a loop- type interface. A series of organophosphorus compounds were selected a s test analytes; they were monitored using the carbon, sulphur, nitrog en, chlorine, bromine and phosphorus channels. The system showed no fl ame-outs or other maintenance problems even after 300 large-volume inj ections. The analytical potential of the system, expressed in terms of repeatability, linearity and minimum detectable amount, was not affec ted and a 100-fold increase in analyte detectability, in terms of conc entration units, compared with a conventional 1-mu l injection was obs erved. As an application, GC-AED was combined off-line with solid-phas e extraction. Several environmental contaminants were preconcentrated from river and tap water samples, and 20% (100 mu l) of the ethyl acet ate eluent were directly analysed. With a sample volume of only 10 ml, the detection limits of the organophosphorus pesticides typically wer e ca. 0.1 mu g/l.