ONLINE VERSUS OFF-LINE SOLID-PHASE EXTRACTION IN THE DETERMINATION OF ORGANIC CONTAMINANTS IN WATER - ADVANTAGES AND LIMITATIONS

Solid-phase extraction (SPE) has become and important and frequently employed method for the preconcentration of organic pollutants from water samples. From the methodological standpoint, two basic approaches can be recognized, on-line and off-line, each of which has its advantages and limitations. The original off-line modification is simple and highly flexible. Therefore, it is often used in analytical research and in quick testing methods. On the other hand, the possibility of automation and the high sample throughput of on-line SPE are the major reasons for its growing use in routine target analyses and in analytical methods for continuous monitoring of water quality. While the growing interest in automation in laboratory practice leads to promising perspectives for on-line techniques, the relatively unlimited flexibility of the classical off-line SPE makes it always a suitable procedure to be used for trace enrichment purposes in diverse analytical applications. This paper gives an overview of the basic principles and possibilities of both off-line and on-line SPE approaches and provides a brief survey of their benefits and limitations.