The Determination of Ascorbates in Beer by Liquid Chromatography with Electrochemical Detection. E. J. Knudson and K. J. Siebert, The Stroh Brewery Company, Detroit, MI. J. Am. Soc. Brew. Chem. 45:0033, 1987.

A liquid chromatography/electrochemistry technique for the determination of nonoxidized ascorbates was shown to work for beer and other beverage samples. The method is rapid, very selective, and has a limit of detection of 0.17 mg/L of ascorbic acid or isoascorbic acid in aqueous samples and of 0.28 mg/L in beer. Coefficients of variation for ascorbate and isoascorbate are between 1.4 and 3.2% over the range of 5-30 mg/L. Interferences are minimal. The technique can be used to monitor the effects of shelf storage on ascorbate levels in packaged beer. The identity of the particular ascorbate species used (ascorbic acid or isoascorbic acid) can be established by coinjecting a known standard with the beverage containing the unknown compound, then plotting the second derivative of the chromatogram. This method will distinguish two overlapping peaks with a resolution as low as 0.5 and peak area ratios as large as four or five to one.

Keywords: Ascorbic acid, Isoascorbic acid, Detection of overlapping chromatographic peaks, Storage time and temperature