Simple, rapid determination of lecithin and sphingomyelin in amniotic fluid.

We describe a rapid and very sensitive modified determination of lecithin and sphingomyelin in amniotic fluid. It requires 1.5 ml of amniotic fluid and can be done in less than 40 mm. Modifications include “Instant Thin Layer Chromatography” plates (Gelman) with a punched disc system of sample application, as well as elimination of the acetone wash steps, and substitution of Rhodamine B dye for the corrosive sulfuric acid char technique of detection. The procedure can be quantified, and exact concentrations of lecithin in amniotic fluid can be determined by a standard addition procedure, or from a standard curve.