(3-sn-Phosphatidyl)cholines (lecithins) in amniotic fluid.

Many currently used thin-layer chromatographic methods for phospholipid assay rely on charring the developed plate in the presence of cupric acetate. Saturated acyl phospholipids do not react. We find that substitution of cupric sulfate results in detection of both saturated and unsaturated phospholipids. By exploiting the difference with the two reagents, one can separately estimate the amounts of saturated phospholipid. The method described here is reproducible, and we illustrate its use in determinations of (3-sn-phosphatidyl)cholines (lecithins) in amniotic fluid from problem pregnancies.