PROTOCOL FOR THE ANALYSIS OF HIGH-CONCENTRATIONS OF BENZENE, TOLUENE,ETHYLBENZENE, AND XYLENE ISOMERS IN WATER USING AUTOMATED SOLID-PHASEMICROEXTRACTION-GC-FID

Analysis of benzene, toluene, ethylbenzene, and xylene isomers (BTEX) in water using automated solid-phase microextraction (SPME) has been s hown to be fast and efficient. However, environmental samples containi ng free-phase or high concentrations of BTEX must be diluted before an alysis can proceed. A protocol based on two dilutions, the first dilut ion using acetone and the second with distilled water, is described. S eparatory funnel experiments indicated the aqueous solubilities of BTE X compounds in a complex mixture can be estimated using Raoult's law. The linear relationship of concentration as a function of response wit h SPME was more accurate for equal weight BTEX mixtures with concentra tions less than or equal to 10 mg/L than for concentrations up to 200 mg/L. It is recommended to dilute high-concentration BTEX samples belo w the aqueous solubility indicated by Raoult's law to ensure accurate quantification. Using this dilution protocol, remediation projects wit h samples containing free-phase or high concentrations of BTEX can rou tinely use the SPME-GC-FID analysis method.