A flow-batch analyzer for UV-Vis spectrophotometric detection of adulteration in distilled spirits

Abstract

Um analisador flow-batch é proposto para detecção de adulterações em bebidas destiladas (uísque, conhaque, cachaça, rum e vodca) usando espectrofotometria UV-Vis. O analisador foi empregado para diluir as amostras não-adulteradas e para simular adulterações com adição de 5 e 10% (v/v) de água, etanol ou metanol. Modelos de classificação SIMCA (soft independent modelling of class analogies) foram construídos empregando espectros de amostras adulteradas e não-adulteradas na faixa de 235-355 nm. Aplicando-se os modelos SIMCA a um conjunto de teste, todas as amostras adulteradas e não-adulteradas foram corretamente discriminadas com um nível de confiança de 95% e uma frequência analítica superior a 120 amostras por hora.An automatic flow-batch analyzer is proposed for detection of adulteration in distilled spirits (whiskey, brandy, cachaça, rum and vodka) using UV-Vis spectrophotometry. The analyzer was employed to dilute the non-adulterated samples and to simulate adulteration with addition of 5 and 10% (v/v) of water, ethanol or methanol. SIMCA (soft independent modelling of class analogies) classification models were built using spectra of non-adulterated and adulterated samples in the region of 235-355 nm. By applying the SIMCA models to a test set, all adulterated and non-adulterated samples were correctly discriminated at a confidence level of 95% with an analytical throughput larger than 120 samples per hour.Keywords: flow-batch analyzer, SIMCA, UV-Vis spectrophotometry, adulteration of distilled spirits, screening analysis IntroductionThe adulteration of distilled spirits with water, ethanol or methanol is a problem with serious repercussions, which compromises the product quality, leads to loss of tax revenue and may constitute a public health threat. [1][2][3][4][5] In a study concerning the chemical composition of 608 beverage samples retailed in Brazil over the period [1993][1994][1995][1996][1997][1998][1999] 391 samples were found to be out of quality standards. 5 In two cases, the methanol levels were above the tolerance limit stated in Brazilian legislation. In that study, the analyses were carried out by chromatography in gaseous phase with a flame ionization detector.Chromatography is a powerful analytical method, which has been used in several works to detect adulteration in distilled spirits.6-8 However, such method presents some disadvantages, including high cost of the instrumentation, low analytical throughput, high consumption of reagents and samples and generation of harmful residues. 5,9 These limitations have motivated the development of spectrophotometric techniques for screening analysis [10][11][12][13][14][15][16][17][18][19] with the aim of reducing the number of samples that need to be analyzed by chromatographic methods. In this context, chemometrics plays a key role in the achievement of good screening results. [10][11][12] A previous work 10 proposed the use of near-infrared spectroscopy (NIR) and chemometrics to classify 69 samples of distilled spirits with respect to type (whi...

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