Determination of phenols in water using liquid phase microextraction with back extraction combined with high-performance liquid chromatography

Liquid phase microextraction with back extraction (LPME/BE) combined with h igh-performance liquid chromatography (HPLC) was studied for the determinat ion of a variety of phenols in water samples. The target compounds were ext racted from 2-ml aqueous sample adjusted to pH 1 (donor solution) through a microliter-size organic solvent phase (400-mul n-hexane), confined inside a small PTFE ring, and finally into a 1-mul basic aqueous acceptor microdro p suspended in the aforementioned solvent phase from the tip of a microsyri nge needle. After extracting for a prescribed time, the microdrop was taken back into the syringe and directly injected into an HPLC for detection. Fa ctors relevant to the extraction procedure were studied. At the optimized e xtraction conditions, a large enrichment factor (more than 100-fold) can be achieved for most of the phenols within 35 min. The detection limit range was 0.5-2.5 mug/l for different analytes in aqueous samples. The results de monstrate the suitability of the LPME/BE approach to the analysis of polar compounds in aqueous samples. (C) 2001 Elsevier Science B.V. All rights res erved.