Simultaneous extraction and concentration by on-line hollow fiber membrane extraction

In the determination of trace-level pollutants in water, a concentration step is usually needed between extraction and analysis. In this paper, simultaneous extraction and concentration during on-line analysis using hollow fiber membranes is reported. Solvent loss across the membrane resulted in simultaneous concentration during extraction and had pronounced influence on enrichment factor and extraction efficiency. This phenomenon is an important consideration for analytical methods employing solvent extraction across a membrane, because it is possible to eliminate the concentration step. Continuous on-line monitoring of semivolatile compounds was achieved using this approach, and the effects of process variables on enrichment and extraction efficiency were studied. It was found that enrichment increased with solvent loss, even when the extraction efficiency decreased.