Total phospholipid analysis in human milk without acid digestion

Abstract

A colorimetric method for measuring the organic phosphorus in human milk without acid digestion was studied. Human milk samples were assayed and compared to phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin standards. Spectral and calibration curves prepared from phospholipid standards were equivalent. Absorption maxima occurred between 720 and 740 nm. A reproducibility study of twenty total lipid samples had a coefficient of variation of 3.8%. Phosphorus ranged from 4.7 to 5.5 micrograms with a mean +/- SD of 5.2 +/- 0.2 micrograms P. The recovery of phosphatidylcholines added to 10 mg samples of human milk triacylglycerols ranged from 99.0 to 102.1%. The results from the new method were comparable to those obtained by a modified Fiske and Subbarow method for measuring inorganic phosphorus after sulfuric acid digestion of the milk lipids. We concluded that the new method provides a satisfactory alternative for the determination of organic phosphorus in human milk.