TRENDS IN EXTRACTION OF SEMIVOLATILE COMPOUNDS FROM WATER FOR ENVIRONMENTAL-ANALYSIS

Semivolatile compounds generally lack sufficient vapour pressure and/o r are too water soluble to be isolated by gas-phase purging methods. T he conventional isolation techniques usually employed are liquid-liqui d extraction and solid-phase extraction (SPE). Health and cost concern s associated with the use of large solvent volumes as well as the agre ed phasing out of certain common water immiscible solvents have conspi red to make this approach less attractive and have engendered efforts to find alternative solutions. SPE has emerged as the preferred choice ; initially using small cartridge devices,(1) and in recent years part icle-loaded membranes,(2) particle-embedded glass fibre discs,(3) poly mer-coated glass fibres (solid-phase micro-extraction; SPME),(4) and o pen-tubular extraction columns.(5) Supported liquid membranes (SLMs) r epresent a further approach to liquid extraction that is economical in the consumption of solvents and frequently involves the selective tra nsfer of analytes between two totally aqueous systems.(6) We will also address the issue of sample utilization based on large volume injecti on in GC to replace off-line solvent evaporation methods.