Flow injection, amperometric determination of ethanol in wines after solid-phase extraction

Ethanol in wines was determined by flow injection analysis with an amperometric detector using an oxidized nickel wire. Solid-phase extraction with a strong anion exchanger was used to remove interferences such as organic acids from the matrix, and the residue of the extraction was injected directly into the FIA system. The recoveries of ethanol from wines spiked with standards ranged from 101% to 103%. The response of the nickel electrode to ethanol is dependent on the applied potential and the pH of the carrier. The optimal conditions for the detection of ethanol were an applied potential of +0.60 V (vs. Ag/AgCl) in a carrier of 100 mM sodium hydroxide solution. The electrode exhibited a linear response from 10−5 to 10−3 M, with a detection limit of 1 × 10−6 M. The method was demonstrated by the determination of ethanol in wines.