Extraction preconcentration of phenol from aqueous solutions using n-butyl acetate for GC-MS analysis

A streamlined sample preparation procedure was developed and evaluated for the determination of phenol in water by gas chromatography-mass spectrometry (GC-MS). Phenol was isolated in a single liquid-liquid extraction using n -butyl acetate, with sodium chloride added as a salting-out agent. n -Butyl acetate was selected following comparison with ethyl acetate and diethyl ether. The salting-out study showed that salt content affects both the analytical response of phenol and the volume of the organic phase that can be recovered. These effects were therefore considered jointly when selecting the extraction conditions. The working procedure used 36 g of NaCl and 1.5 mL of n -butyl acetate per 100 mL of acidified water sample. Calibration using aqueous standards subjected to the entire sample preparation procedure was compared with calibration solutions prepared directly in n -butyl acetate. This comparison gave an estimated fraction of phenol transferred to the organic phase of 37.7%. The key feature of the proposed approach is the integrated evaluation of extraction-based preconcentration, taking into account the analytical response, the recoverable organic-phase volume, and incomplete analyte extraction. Because extraction losses are incorporated into the procedural calibration, quantitative determination does not require complete transfer of phenol to the organic phase. The procedure uses readily available reagents and yields an extract that can be analysed directly by GC-MS without derivatization, back-extraction, or solvent evaporation, thereby reducing the number of sample preparation steps.