Determinations of Organic Acids in Potatoes by High Performance Liquid Chromatography

A high performance liquid chromatographic method has been developed to quantify the major organic acids in potatoes oxalic, citric, malic, fumaric and ascorbic acids. Tubers were extracted with 95% ethanol:water:concentrated sulfuric acid 60:40:0.2 followed by injection on an Aminex HPX-87 column with a mobile phase of 0.018N sulfuric acid. Ascorbic acid was detected at 260 nm while the other four acids were quantified at 210 nm unless fructose was present at a concentration of 6 mg/g or higher, in which case 220 or 230 nm was used. Greater than 90% recovery was observed for all acids with most recoveries near 100%. The method has been shown to be very reproducible with the CV% ranging from 1.3-12.3 while the majority were below 4%. Analyses of several potato varieties have shown a wide variation in acid content among varieties.