The analysis of dietary supplements is far less regulated than pharmaceuticals, leading to potential quality issues. Considering their positive effect, many athletes consume supplements containing L-histidine and β-alanine. A new microfluidic method for the determination of L-histidine and β-alanine in dietary supplement formulations has been developed. For the first time, capacitively coupled contactless conductivity detection was employed for the microchip electrophoresis of amino acids in real samples. A linear relationship between detector response and concentration was observed in the range of 10-100 µmol L-1 for L-histidine (R2 = 0.9968) and β-alanine (R2 = 0.9954), while achieved limits of detection (3 × S/N ratio) were 4.2 µmol L-1 and 5.2 µmol L-1, respectively. The accuracy of the method was confirmed using recovery experiments as well as CE-UV-VIS and HPLC-UV-VIS techniques. The developed method allows unambiguous identification of amino acids in native form without chemical derivatization and with the possibility of simultaneous analysis of amino acids with metal cations.

Department of Analytical and Environmental Chemistry Faculty of Sciences University of Pécs Ifjúság útja Pécs 7624 Hungary

Department of Analytical Chemistry Faculty of Science Charles University Hlavova 8 12843 Prague 2 Czech Republic

Department of Biotechnology University of Rijeka Radmile Matejčić 2 HR 51000 Rijeka Croatia

Department of Chemistry Josip Juraj Strossmayer University of Osijek Cara Hadrijana 8 HR 31000 Osijek Croatia

Department of Food Technology University North Trg dr Žarka Dolinara 1 HR 48000 Koprivnica Croatia

Doctoral School of Chemistry University of Pécs Ifjúság útja Pécs 7624 Hungary

Faculty of Geotechnical Engineering University of Zagreb Hallerova 7 HR 42000 Varaždin Croatia

Institute of Bioanalysis Medical School Szentágothai Research Center University of Pécs Pécs Hungary

Pirelli Deutschland GmbH Höchster Straße 48 60 64747 Breuberg Germany

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