Chemometric analysis of square wave voltammograms for classification and quantitation of untreated beverage samples

Square wave voltammetry at platinum electrodes of 55 untreated liquid samples, including wines, beers, coffees, milks and fruit juices was performed, and the resulting voltammograms were analyzed using principal components analysis (PCA). Pattern recognition, using plots of the first two principal components, as well as cluster analysis, was used to determine subpopulation groupings. Variable selection, using subsets of the complete voltammograms, allowed finer classification of nonalcoholic beverages based on type and brand. Principal components regression (PCR) and partial least squares (PLS) were applied to voltammograms of diluted pure orange juice samples to determine whether adulteration can be detected by these methods. RMS errors in volume fractions in the calibration set were 2.0% and 1.8%, respectively, for PCR and PLS, and 4.0% (PCR) and 5.4% (PLS) in the validation set.