Spectrophotometric analysis of alpha- and beta-naphthol mixtures applying partial least-squares method

Pharmaceutical and other chemical industries often require high purity of a lpha-naphthol (alpha N) because it is used like a precursor for further syn thesis. The determination of beta-naphthol (beta N) in mixture with alpha N by spectrophotometry applying partial least-squares procedure was develope d. Using the partial least-squares calibration, a model based on calibratio n measurement was developed and, afterwards, used to predict the test set ( samples). Normal or derivative spectra in lambda-ranges a) 190-250 nm or b) 260-345 nm were used. The method is suitable for fast determination of bet a N in mixtures with alpha N with relative standard deviation around 2 % fo r beta N (if the content is higher than 1.5-3.0 %). Both studied lambda-ran ges can be used for the determination, but derivative spectra are advantage ous for the 190-250 nm region.