Selective and simultaneous determination of total chlorogenic acids, vanillin and caffeine in foods and beverages by adsorptive stripping voltammetry using a cathodically pretreated boron-doped diamond electrode

The present study describes a convenient method for the selective and simultaneous determination of 5-O-Caffeoylquinic acid (5-CQA) that is major compound of chlorogenic acids (CGAs) in coffee, vanillin (VAN) and caffeine (CAF) at an unmodified boron-doped diamond (BDD) electrode using square-wave adsorptive stripping voltammetry. The effect of pretreatment (anodically or cathodically) of BDD electrode was investigated in detail on the stripping voltammetric performance for all compounds. Cathodic pretreatment was found to be best choice with respect to better peak potential separation and higher peak current intensity. Three very well-resolved and reproducible oxidative processes of 5-CQA, VAN and CAF were found at +0.68, 1.15 and 1.50 V (after 60 s accumulation under open-circuit voltage), respectively, in 0.1 M HNO3. Linear calibration plots were obtained for simultaneous determination of 5-CQA, VAN and CAF in the concentration ranges of 2.8 x 10(-6)-1.7 x 10(-4), 3.3 x 10(-6)-3.3 x 10(-4), and 5.2 x 10(-7)-2.1 x 10(-4) M, with detection limits of 4.0 x 10(-7), 3.8 x 10(-7), and 1.5 x 10(-7) M, respectively. The potential applicability of the proposed method was illustrated in commercial food and beverage samples. As far as it could be verified, the proposed analytical method is the first one based on the simultaneous determination of 5-CQA, VAN and CAF. (c) 2017 Published by Elsevier B.V.