Direct Analysis of Lactose in Milk and Serum

Abstract

This note presents a revision of the phenol-sulfuric acid method of Dubois et al. (Anal. Chem. 28: 350. 1956) and stresses the importance of adhering to optimum reagent levels to avoid analytical variation. For lactose, the phenol concentration should be between 5 and 12 mg per ml of total arithmetic volume, while sulfuric acid should comprise from 70 to 75% v/v of the total. In the recommended procedure, 11 mg of phenol and 0.74 ml of concentrated sulfuric acid are used per ml of total arithmetic volume.