Trace determination of phenol, bisphenol A and bisphenol A diglycidyl ether in mixtures by excitation fluorescence following micro liquid–liquid extraction using partial least squares regression

Abstract

The determination of phenol, bisphenol A and bisphenol A diglycidyl ether in mixtures was carried out by recording excitation fluorescence spectra between 245 and 290 nm with an emission wavelength of 306 nm. The proposed method involves a micro liquid–liquid extraction of sodium chloride saturated water samples with diethyl ether followed by direct fluorimetric analysis of the extracts in a 10 mm quartz cell with a 2 mm inside width and a volume of 400 µl. The excitation–emission spectra of these compounds overlap considerably, which does not permit their direct determination without previous separation by conventional methodologies. A method is proposed for the determination of these compounds by the use of a full-spectrum multivariate calibration method, partial least squares (PLS). A comparison between two PLS algorithms with different pre-processing methodologies was made. The experimental calibration matrix was designed with 19 samples. The concentrations were varied between 3.0 and 18.0 µg l^–1 for phenol, 3.0 and 13.0 µg l^–1 for bisphenol A and 5.0 and 30.0 µg l^–1 for bisphenol A diglycidyl ether. The cross-validation method was used to select the number of factors. The proposed method, which applied the PLS-1 model with mean centred data, was used for the determination of these compounds in previously spiked water. The predicted concentrations were satisfactory in all cases.