Wavelength region selection and spectrophotometric simultaneous determination of naphthol isomers based on net analyte signal

Naphthol isomers were simultaneously and spectrophotometrically determined in wastewater, using a model based on net analyte signal (NAS). The calibration method used is a variation of the original hybrid linear analysis method as proposed by Goicoechea and Olivieri (HLA/GO). Owing to spectral interferences, the simultaneous determination of mixtures of naphthol isomers, using a spectrophotometric method, is difficult. A rapid and powerful method was used for wavelength selection in the modeling step, based on the minimization of the error indicator (EI), which was estimated as a function of the moving spectral region. The calculation of the net analytical signal using a modified HLA/GO method allows us to determine several figures of merit, as selectivity, sensitivity, analytical sensitivity and limit of detection of the proposed multivariate calibration. The limit of detection (LOD) for 1 and 2-naphthol were 0.04 and 0.06 (μg/mL) respectively. The proposed model was tested in the analysis of wastewater samples, without previous sample preparation steps, obtaining recovery values between 98 and 104.00%, for 1-naphthol and between 97.00 and 103.00%, for 2-naphthol.