Simultaneous measurement of lecithin, sphingomyelin, phosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine, and phosphatidylserine in amniotic fluid.

A one-dimensional thin-layer chromatographic method is described by which the ratios and proportions of lecithin, sphingomyelin, phosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine, and phosphatidylserine in amniotic fluid may be simultaneously determined. Commercial chromatographic plates, 10 X 7.5 cm, pretreated with cupric chloride, are used. The solvent system is chloroform/methanol/ammonium hydroxide (30/17/1.5 by vol). The plates are sprayed with a cupric acetate (350 g/L)/phosphoric acid (80 mL/L) reagent and charred on a hot plate to make the phospholipids visible. The percentage of each phospholipid present is determined by direct reflectance or transmission densitometry. The correlation coefficients for the lecithin/sphingomyelin, phosphatidylinositol/sphingomyelin, and phosphatidylglycerol/sphingomyelin ratios of the two scanning methods are 0.971, 0.980, and 0.955, respectively, for between-day analyses.