Quantification of BTEX compounds in model effluent systems using flow injection diode-array spectrophotometry and multivariate calibration

Abstract

The potential of applying flow injection (FI) analysis in combination with diode-array spectrophotometry (in the range 200–300 nm) and multivariate calibration to the on-line analysis of BTEX compounds in effluents has been investigated, using synthetic mixtures of toluene, ethylbenzene and o-xylene in aqueous solution (0–20 mg 1–1). Absorbance and first- and second-derivative spectral data have been modelled using stepwise multiple linear regression (SMLR), principal components regression (PCR) and partial least-squares regression (PLS1). Predictions of individual analyte concentrations in test samples produced prediction errors ranging from 8.5% for o-xylene to 45.8% for toluene. The lowest prediction errors (7.0%) were produced when calibrating the three compounds as a single component (‘total TEX’). In order to analyse industrial effluents, an FI manifold incorporating a solvent extraction cell was used to reduce matrix interferences. This method was successfully used for the analysis of both aqueous standards and solutions of a real effluent spiked with o-xylene. In each case, hexane was used to extract o-xylene from the aqueous matrix.