ABSTRACT
From the above-reported studies, it is clear that sample preconcentration and cleanup are necessary to reach the low detection limits required in environmental analysis. Two possible types of trace enrichment exist: the off-line trace enrichment and the on-line Bellar and Budde [20] used the first type of method to determine nonvolatile target compounds in aqueous environmental samples. They used liquid-liquid and liquid-solid extraction and subsequent gradient LC separation for a water sample spiked with carbamate, triazine, sulfonylurea, phenylurea, and organophosphorous pesticides. With the first type of procedure, detection limits for 34 analytes varied from 0.2 J.lg/liter for cyanazine to 18 J.lg/liter for linuron in the filament-off and positive ion mode; using the liquid-solid extraction, the detection limits were approximately 10 times higher. Combining retention time data and molecular-mass information from the [M + H]+ and [M + NH4]+ ions and the evidence from isotope patterns provided satisfactory information for the identification of target analytes.
