ANALYSIS OF 23 POLYNUCLEAR AROMATIC-HYDROCARBONS FROM NATURAL-WATER AT THE SUB-NG L LEVEL USING SOLID-PHASE DISK EXTRACTION AND MASS-SELECTIVE DETECTION/

An Empore disk extraction method for the analysis of 23 polynuclear ar omatic hydrocarbons (PAHs) in natural waters at ng/l levels is describ ed. Experimental variables investigated include determination of solve nt type, extraction number, preconditioning requirements, breakthrough and the use of an in-line drying agent. The stability of PAHs stored extracted on Empore disks compared to samples left unextracted is demo nstrated. Disks stored at -19 degrees C for 60 days had higher recover ies than samples left in sampling bottles unextracted at 4 degrees C. In general, less decomposition of the target analytes occurred when ex tracted and stored on the disks. The accuracy of the method was evalua ted through the use of certified reference material analyzed as blind samples. The Empore disk extraction method achieved equivalent or bett er detection limits, used significantly less amounts of solvent, and w as faster to use than traditional liquid-liquid methods. Method detect ion limits for the 23 PAHs ranged from 9 to 56 ng/l.