A Study of the Starch-Iodine Complex: A Modified Colorimetric Micro Determination of Amylase in Biologic Fluids

Abstract

The limitations, inaccuracies, and practical difficulties of saccharogenic methods are discussed. A modified colorimetric microdetermination of amylase is described in which the digestion of starch is measured by the decrease in the starch-iodine color. Experimental data show that there are two other serum factors that can also cause a fall-off in color: (1) an immediate 10-15% depression of color, probably due to serum proteins and countered by using serum in the control; (2) an acid-serum factor causing a progressive fall-off in color subsequent to the initial depression. Iodine prevents this, and must be added as soon as the acid has been added to stop the enzyme activity. Results of 189 consecutive assays of human sera are presented. Amylase activity of duodenal aspirate has been determined simultaneously by the method described and the Lagerlöf method. Results are compared. Changes in serum amylase and lipase levels in artificially produced pancreatitis in dogs are presented. Optimal conditions for amylase activity are reviewed, and in the light of these, different amyloclastic methods and their results compared. Achroic-point technics are briefly evaluated.