IMPROVEMENT OF ONLINE SOLID-PHASE EXTRACTION FOR DETERMINING PHENOLIC-COMPOUNDS IN WATER

Modifying the most common design for the on-line coupling of a precolu mn to reversed phase LC with diode array detection has resulted in red uction of the broadening of the peaks which results when the compounds of interest are strongly retained by a highly hydrophobic sorbent. Th e modification consists of the desorption of the analytes trapped on t he precolumn solely by the organic solvent used to modify the solvent strength of the mobile phase. Results obtained using this design were compared with those obtained with the conventional design, with C-18 a nd PLRP-S precolumns. The performance of the system was also tested wi th a highly cross-linked styrene-divinylbenzene copolymer (ENVI-chrom P) precolumn for the determination of phenolic compounds in real sampl es. The advantages and disadvantages are discussed. Ion-pair solid pha se extraction is used in order to increase the breakthrough volumes of more polar compounds, mainly phenol. The use of the new design enable s phenolic compounds to be determined at the low mu g L(-1) level with limits of detection ranging between 0.1 and 2 mu g L(-1) in tap water when a 10 mL sample was analyzed.