The Quality Determination of Selected Commercial Online Purchased Edible Pomegranate Seed Oils With New Argentometric Liquid Chromatography Method

The number of online-purchased dietary supplements of diversified origin is exponentially increasing. Pomegranate seed oils (PSOs)—the main dietary source of conjugated linolenic acids (CLnA)—are available as dietary supplements via the Internet. PSO samples (<i>n</i> = 24) were purchased from Internet shops in Poland and China. Chromatographic techniques (gas chromatography coupled with mass spectroscopy [GC-MS] for fatty acids [FAs], liquid chromatography with fluorescence detection for tocopherols, and high-performance liquid chromatography with photodiode array detection for conjugated FAs) were used. The GC-MS method enabled the quantification of 45 FAs, which indicates its superiority to previously used methods. Argentometric liquid chromatography with pre-column mild alkaline hydrolysis for analysis of structural isomers of CLnA does not need preliminary derivatization into volatile compounds, which ensures the absence of artifacts and enables the analysis of the entire conjugated FA profile. PSO differed with tocopherols and FA profile. Some PSOs contained negligible amounts of CLnA, and because of that they did not meet the criteria of valuable, unadulterated nutraceuticals. Obtained results indicate that online purchased PSO shipped from distant places of origin could have been stored in inadequate conditions (temperature, humidity), which caused i.a. deterioration of oxidative quality. Unregulated online availability of dietary supplements of low oxidative quality and nutritive value as well as their intake may be a risk rather than a benefit for consumers. Argentometric liquid chromatography can be a simple, selective, and sensitive tool for screening of dietary supplements containing conjugated FAs and should be considered as an essential way of quality assurance.