Simultaneous spectrophotometric determination of the three structural isomers of cresol using multivariate regression methods

The simultaneous determination of the structural isomers of cresol was carried out using UV spectrophotometry by applying the principle component regression (PCR) and partial least squares (PLS) regression methods. Different concentration levels of cresol isomers were determined in their mixtures by construction of a partial factorial calibration design at four levels. Both multivariate calibration models were constructed using the correlation between the concentration and absorbance data matrices in the spectral region 283-305nm. The methods were validated by analyzing an independent validation set solutions of the same compounds. The methods were found to be accurate and precise as indicated by the mean % recovery (99.96-100.41%) and % relative standard deviation (0.15-0.72%), respectively. The methods were applied to the determination of cresol isomers in a topical veterinary preparation. The methods were proved to be applicable to the determination of the three cresol isomers without prior separation procedures, despite of the extensive spectral overlap of such compounds.