Preparation of Tissue Extracts for the Determination of Malic Acid* by Lawrence

Hummel’s (1) fluorometric determination of malic acid requires the precipitation of calcium malate by alcohol as a means of fractionation from biological materials. Fructose-l, 6-diphosphate, glucose-6-phosphate, or glycogen if present must be removed. Below is described a method for preparing extracts of tissues which applies the principles of chromatography on silica gel. Osazone formation, precipitation of malate, and preliminary hydrolysis for the removal of glycogen are thereby eliminated, since interfering carbohydrates do not appear with malic acid in the chromatographic zone selected. When the same chromatographic column that is employed for the preparation of the malate for analysis separates simultaneously other acids of the Krebs cycle (2)) the determination has enhanced utility.