RESUMO
BACKGROUND: Dietary supplements (DS) containing undeclared substances may pose serious risk to s public health. The consumers of DS should be aware of such products in order to avoid the risk of fatal outcomes. AIM OF THE STUDY: The study is based on the determination and identification of undeclared substances - theobromine (TB), theophylline (TH), pseudoephedrine (PE), caffeine (C), hydrochlorothiazide (HTZ) and yohimbine (Y) - in market-available DS. MATERIAL AND METHODS: Ultra-high-performance liquid chromatography with diode array detection (UHPLC-DAD) was utilized to identify and quantify the presence of undeclared substances, in 52 different DS collected from the market. RESULTS: A fast and reliable UHPLC-DAD method was developed and validated for simultaneous determination of the analyte where an efficient separation was achieved within 7 min runtime (TB 1.47, TH 1.79, PE 2.08, C 2.26, HTZ 3.78, Y 6.50) with resolution >1.5. The method validation produced r2 values ranging from 0.975 to 0.999 within a linearity range of 1-300 ppm. The UHPLC method revealed the presence of undeclared substances in 11 samples (HD3, HD4, HD9, HD13, HD14, HD15, HD21, HD24, HD27, HD38 and HD40), where the most widely distributed analyte was PE and C. The analyte found to have the highes concentrations (mg) in these DS were PE (11) and C (2.01). Among the 52 DS products tested, the product HD3 revealed a greater number and amount (mg) of undeclared substances, i.e. TH (0.05), C (2.01), HTZ (0.37) and Y (0.05), followed by HD14, i.e. PE (9.31), C (0.40), HTZ (0.01) and HD9 PE (11.00), C (0.41). CONCLUSION: The abundance of undeclared substances in these DS products was PE > C > Y > HTZ. None of the DS contained TB whereas TH was present in only one sample.