A simplified procedure for lipid phosphorus analysis shows that digestion rates vary with phospholipid structure

A simplified procedure for lipid digestion, well suited for handling a large number of samples, was used to analyze a variety of common phospholipids. This procedure involves digestion of phospholipids in perchloric acid at 130 degrees C with minimal sample manipulation. For all lipids tested, complete destruction, needed for quantitation of phosphate, was achieved after a few hours of digestion under these conditions. Rates of phospholipid destruction, monitored by the spectrophotometric quantitation of released phosphate, varied with lipid structure. Phosphatidic acid (PA), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG) and phosphatidylinositol (PI) were found to release phosphate faster than phosphatidylserine (PS), phosphatidylethanolamine (PE) and phosphatidylcholine (PC). Although these differences may vary depending on the digestion conditions, they suggest that care should be exercised in lipid phosphate analyses to insure complete digestion.