Dynamic single-interface hollow fiber liquid phase microextraction of Cr(VI) using ionic liquid containing supported liquid membrane.

The concept of dynamic single-interface hollow fiber membrane liquid-phase microextraction (HF-LPME), where the target analyte was extracted on-line and eluted inside the lumen of the HF membrane, was explored. An ionic liquid containing supported liquid membrane was used for the trace determination of Cr(VI) as a model compound. Since the extraction took place on-line inside the hollow fiber membrane, the mass transfer behavior was described and discussed in comparison with the conventional HF-LPME. The extraction efficiency was improved by a recirculation configuration of the sample solution at relatively high sampling flow rates as a result of the increased effective contact area. The positive pressure observed to be built up during extraction was overcome by a flow-balancing pressure design. The dynamic single-interface HF-LPME method with an enrichment factor of 41, a detection limit of 1.2µgL-1 and determination limit of 4.0µgL-1 was successfully applied to the reliable determination of Cr(VI) from environmental water samples. The quantification limit is below the maximum contaminant level in drinking water, set at 10µgL-1 of hexavalent chromium by the California Environmental Protection Agency.