Pre-concentration of phenolic compounds in water samples by novel liquid-liquid microextraction and determination by gas chromatography-mass spectrometry

Pre-concentration and determination of 8 phenolic compounds in water samples has been achieved by in situ derivatization and using a new liquid-liquid microextraction coupled GC-MS system. Microextraction efficiency factors have been investigated and optimized: 9 mu L 1-undecanol microdrop exposed for 15 min floated on surface of a 10 mL water sample at 55 degrees C, stirred at 1200 rpm, low pH level and saturated salt conditions. Chromatographic problems associated with free phenols have been overcome by simultaneous in situ derivatization utilizing 40 mu L of acetic anhydride and 0.5% (w/v) K2CO3. Under the selected conditions, pre-concentration factor of 235-1174, limit of detection of 0.005-0.68 mu g/L (S/N=3) and linearity range of 0.02-300 mu g/L have been obtained. A reasonable repeatability (RSD <= 10.4%, n=5) with satisfactory linearity (0.9995 >= r(2) >= 0.9975) of results illustrated a good performance of the present method. The relative recovery of different natural water samples was higher than 84%. (C) 2009 Elsevier B.V. All rights reserved.