Teaching food analysis through unknowns: Study case for methylxanthines, organic acids, and sugars examination over liquid chromatography

Three laboratory sessions are described, each one focused on a distinct group of analytes (i.e., 1. Methylxanthines, 2. Organic acids 3. Sugars). To study each analyte group, food profiling was achieved using liquid chromatography; where each analyte (n = 3, 15, and 5 analytes for methylxanthines, organic acids, and sugars, respectively) was identified and quantified. Different food samples (including beverages, powders, cereals, and dairy products) were given to students who within each class knew the possible identities of the group of samples given but had to pair, after examination, the resulting profiles obtained with each food sample as the food samples were unidentified (unknowns). Quali/Quantitative data were recollected from the resulting chromatograms after each food was subjected to analysis. For organic acids, solid phase extraction and potentiometry were used as tools to demonstrate separation science from colored drinks as sample pretreatment and as a classic alternative for instrumental analysis.