Determination of chlorophenolics in waters by membrane solid-phase extraction: comparison between C-18 and activated carbon membranes and between modes of extraction and elution

Chlorophenols, chlorocatechols and chloroguaiacols were spiked at the 1 ppb level into water samples containing up to 50 ppm dissolved organic carbon, acetylated in situ and extracted onto C-18 and activated carbon (AC) membr anes by dynamic or static sorption. Recovery of the analytes from the membr anes was carried out by either static (in-vial elution) or dynamic desorpti on (elution) using either acetone or toluene. Extracts were analysed by gas chromatography-mass spectrometric detection (GC-MSD). C-18 membranes gave recoveries of between 70 and 102% for all compounds with the exception of p henol, when using dynamic desorption with acetone as the eluting solvent. S tatic desorption using C-18 membranes gave satisfactory recoveries (65-80%) for chlorophenols. AC membranes gave quantitative recoveries for all compo unds when using dynamic desorption with toluene. Static desorption using AC membranes:resulted in low recoveries (<60%) for all compounds except pheno l. A combination of a C-18 membrane placed on top of the AC membrane during dynamic extraction was tested to increase retention of phenol. Dynamic des orption of both membranes in the reverse direction (AC on top of C-18) usin g 10 mi of acetone or toluene gave quantitative results for all compounds, even in the presence of 50 ppm dissolved organic carbon. (C) 1999 Elsevier Science B.V. All rights reserved.