Combination of Acid-Free Open-Vessel Wet Digestion and Poly(amidoamine) Dendrimer-Enhanced Capillary Electrophoresis for Determination of Metal Ions in Wines

Abstract

We propose a procedure for determination of metal ions, viz., Pb(II), Co(II), Cu(II), Fe(III), and Zn(II), in red and rice wines by acid-free open-vessel wet digestion (AFOVWD) and poly(amidoamine) dendrimer generation 0.5 (PAMAM G 0.5)-enhanced capillary electrophoresis (CE). During sample preparation, the wines were filtrated and then digested in the presence of H2O2, without addition of acid. Therefore, the digested sample solution had low conductivity that would offer the subsequent CE analysis efficient separation and sensitive detection. Moreover, it was found that presence of 2 mM PAMAM G 0.5 in the buffer of 12 mM H3BO3, 7 mM Na2B4O7 and 0.1 mM PAR, at pH 8.8, improved the separation efficiency of all the ions, allowing baseline resolution of the initially overlapped Cu(II) and Fe(III). Importantly, it lowered the detection limit (S/N = 3) of Pb(II) by 5.5-fold, to 128 μg/L, enabling quantitative determination of Pb(II), in addition to Co(II), Cu(II), Fe(III), and Zn(II), in red and rice wines. The results by AFOVWD-CE agreed well with that obtained by inductively coupled plasma–atomic emission spectrometry.