Resolution of phenol, o-cresol, m-cresol and p-cresol mixtures by excitation fluorescence using partial least-squares (PLS) multivariate calibration

Determination of phenol, o-cresol, m-cresol and p-cresol has been carried out in mixtures of up to four components by recording excitation fluorescence spectra between 210 and 285 nm with an emission wavelength of 298 nm. The excitationemission spectra of these compounds are strongly overlapped, which does not permit their direct determination without previous separation by conventional methodologies. Here, a method is proposed for the determination of these chemicals by the use of a full-spectrum multivariate calibration method, partial least squares (PLS). The experimental calibration matrix was designed with 18 samples. The concentrations were varied between 100 and 900 μgl−1 for phenol, 150 and 900 μg l−1 for o-cresol and from 80 to 800 μg l−1 for m- and p-cresol. The cross-validation method was used to select the number of factors. To check the accuracy of the proposed method, the optimized model, obtained using PLS-1, was applied to the determination of these compounds in natural water and soil samples previously spiked with different amounts of each chemical.