Solid-phase microextraction using octadecyl-bonded silica immobilized on the surface of a rotating disk: determination of hexachlorobenzene in water.

Solid-phase microextraction of hexachlorobenzene from water was implemented for the first time on a rotating disk coated with an octadecyl-bonded silica (C(18)) sorptive phase. The results indicate that the sorption performance of this phase for the model analyte selected is similar to that observed using a rotating disk containing PDMS. In both cases, equilibrium is achieved within approximately 120 min for samples volumes of 50 mL and decreases to 20-30 min when the sample volume is decreased to 10 mL. The comparable behavior observed for the sorption of HCB in both phases is consistent with a similar rate-determining step for extraction, which suggests that the overall mass transfer of analyte is not limited by internal diffusion into the phase but by diffusion into the aqueous stagnant layer. The main advantage in the use of the C(18) phase is that the elution of the analyte was achieved in 15 min compared with 45 min for PDMS because, in the case of C(18), dichloromethane can be used as the eluting solvent. The detection limit of the method was 0.08 μg L(-1) HCB for a tap-water sample. The mean recovery for the analyte was 84±2% and 85±3% for the C(18) and PDMS phases, respectively, which indicates good accuracy and precision of the method.