Determination of Phenols in Water Samples using a Supported Liquid Membrane Extraction Probe and Liquid Chromatography with Photodiode Array Detection
A simple, selective and inexpensive miniaturized sample preparation method based on a supported liquid membrane extraction probe is described for the extraction and preconcentration in a single step of phenols in water samples. The phenols were extracted from 5 mL aqueous water samples into 0.4 mL aqueous acceptor phase through the organic membrane. The organic membrane consisted of a porous PTFE membrane impregnated with undecane. In order to obtain a selective extraction and enrichment of the phenols, the conditions were kept such that the phenols were non-ionized in the sample and ionized in the acceptor phase. This was achieved by pH adjustments in the sample and acceptor phases. The method was optimized for its extraction time, depth of the probe in the sample and stirring speed. The detection limit ranged from about 4 μg L–1 for 2-chlorophenol and 2,4-dichlorophenol to 10 μg L–1 for 4-chlorophenol. The resulting enrichment factors were about eight times for 2-chlorophenol and 2,4-dichlorophenol and four times for 4-chlorophenol. The sample preparation method was tested for the determination of phenols in river water samples and landfill leachate. Concentrations of phenols in river water were found to be in the range 4.2 μg L–1 for 2-chlorophenol to 50 μg L–1 for 4-chlorophenol. In landfill leachate, 4-chlorophenol was detected at a concentration of 80 μg L–1.
KEYWORDS: Supported liquid membrane extraction probe, selectivity, chlorophenols, water samples.