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.