Protocol for the Analysis of High Concentrations of Benzene, Toluene, Ethylbenzene, and Xylene Isomers in Water Using Automated Solid-Phase Microextraction−GC−FID

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