Determination of trace amounts of some low molecular weight alcohols in aqueous samples using liquid-phase microextraction and gas chromatography

A new and versatile liquid-phase microextraction method combined with gas chromatography (GC) analysis was applied for the extraction and determination of some aliphatic alcohols. Microlitre volumes of 1-undecanol were delivered on to the surface of the aqueous sample and the sample was agitated for a desired time. Then, the sample vial was cooled by inserting it into an ice bath for 5 min. The solidified solvent was transferred into a suitable vial and immediately melted, of which 1.0 mu L was injected into GC for analysis. The parameters affecting the microextraction efficiency such as sampling temperature, stirring rate, nature and volume of the extracting solvent, salt addition and extraction time were investigated. The optimal microextraction conditions were established as: sample solution temperature, 60 degrees C; stirring rate, 1250 rpm; volume of the extracting solvent, 8.0 mu L (1-undecanol); salt concentration, 4 M NaCl and extraction time of 20 min. Under the optimal conditions, detection limits of the method were in the range of 3-56 mu g L-1 and the relative standard deviations for determination of the alcohols were in the range of 2.2-11.9. Dynamic linearity of the alcohols was found to be in the range of 60-800 mu g L-1. After 20 min of extraction period, the pre-concentration factors for the alcohols were in the range of 13-358. Finally, the method was applied for determination of trace amounts of the alcohols in several real aqueous samples and satisfactory results were obtained.