Loading Concentrations for Tartaric and Malic Acid for Single Column HPLC Organic Acid Analysis

Abstract

The linearity of detection of tartaric and malic acids in grape juice was investigated for a single Aminex HPX 87H organic acid analysis column system. High levels of tartaric and malic acid resulted in a major drop in percent recovery. Using external standard calibration, based on peak height integration, the upper limits for column loading of grape juice samples were found to be 10 µg for tartaric acid and 30 µg for malic acid, above which recoveries dropped below 95%. A similar result was found using a synthetic juice containing glucose, fructose, and the two acids. Aqueous solutions of acids were found to be linear up to 25 µg tartaric acid and 130 µg malic acid. The reason for the drop in recovery under high acid conditions was not identified. Routine grape juice analysis required dilution of 1:10 to 1:20 to ensure accurate recoveries.