Qualitative and quantitative multivariate strategies for determining paprika adulteration with SUDAN I and II dyes

Two strategies based on multivariate qualitative and quantitative analysis are proposed for determining whether paprika samples are adulterated with Sudan I or II dyes. The samples were characterized by their UV-visible spectrum. Then, the following chemometric techniques were applied: principal component analysis (PCA) for the data exploration stage, partial least squares-discriminant analysis (PLS-DA) for the qualitative strategy and partial least squares (PLS) for the Sudan quantification strategy. Three classes were considered in the qualitative analysis: unadulterated, adulterated with Sudan I and adulterated with Sudan II. For the quantitative analysis, models were developed for each adulterant in a concentration range of 0-12 mg g(-1), where 0 mg g(-1) stands for the unadulterated samples. Both strategies gave satisfactory results. The multi-class PIS-DA model properly differentiate between the three types of studied samples: non-adulterated and adulterated with Sudan I and with Sudan II. Only samples at the lowest concentration (1 mg g(-1)) were wrongly detected as unadulterated. The PIS models were validated by setting the regression line of the model-predicted concentration versus the real concentration for the test set samples. The slope and intercept of each regression line were compared with those of the ideal line (0, 1) by means of the joint test of ordinate and slope.