COMPARISON OF REVERSED-PHASE EXTRACTION SORBENTS FOR THE ONLINE TRACE ENRICHMENT OF POLAR ORGANIC-COMPOUNDS IN ENVIRONMENTAL AQUEOUS SAMPLES

On-line sample handling coupling the enrichment of trace organic compounds on reversed-phase sorbents packed in small-size precolumns and their liquid chromatographic separation was investigated. Methods allowing the prediction of breakthrough volumes are reviewed and it is pointed out that the capacity factor of solutes in water, k(w)', is a convenient parameter for predicting the sample volume which can be handled for the preconcentration. A comparison between the main LC-grade sorbents available for the preconcentration of organic compounds in water, alkyl-bonded silicas, non-polar styrene-divinylbenzene copolymers and porous graphitic carbons, is presented. The potential of porous graphitic carbon for trace enrichment of very polar compounds is shown.