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

The determination of phenol, bisphenol A and bisphenol A diglycidyl ether i n mixtures was carried out by recording excitation fluorescence spectra bet ween 245 and 290 nm with an emission wavelength of 306 nm. The proposed met hod involves a micro liquid-liquid extraction of sodium chloride saturated water samples with diethyl ether followed by direct fluorimetric analysis o f the extracts in a 10 mm quartz cell with a 2 mm inside width and a volume of 400 mu l. The excitation-emission spectra of these compounds overlap co nsiderably, which does not permit their direct determination without previo us separation by conventional methodologies. A method is proposed for the d etermination of these compounds by the use of a full-spectrum multivariate calibration method, partial least squares (PLS). A comparison between two P LS algorithms with different pre-processing methodologies was made. The exp erimental calibration matrix was designed with 19 samples. The concentratio ns were varied between 3.0 and 18.0 mu g l(-1) for phenol, 3.0 and 13.0 mu g l(-1) for bisphenol A and 5.0 and 30.0 mu g l(-1) for bisphenol A diglyci dyl ether. The cross-validation method was used to select the number of fac tors. The proposed method, which applied the PLS-1 model with mean centred data, was used for the determination of these compounds in previously spike d water. The predicted concentrations were satisfactory in all cases.