Solid phase extraction (SPE) is an efficient pretreatment method to separate a compound of interest in complicated matrix such as body fluid, food, or in soil. Ultrafiltration is also a suitable pretreatment method to remove higher molecular weight compounds such as protein in body fluid. The latter method is also useful for differential analysis of free type from proteinbound type compound in body fluid. Free type compound after ultrafiltration will exist in filtrate. Previously ultrafiltration and SPE were carried out off-line and the former was done manually, whch was troublesome for routine analysis. In this paper these pretreatment methods were successfully on-line combined and controlled by computer first by the author. Unfortunately this lund of equipment is not currently available in the market yet due to patent restriction.
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