A semi-automated and manual method for determining the total phospholipid phosphorus in amniotic fluid

A rapid method for estimating the total phospholipid content of amniotic fluid has been described that requires 1 ml of sample. Perchloric acid containing a trace of molybdate is the acid digestant for inorganic phosphate release. After digestion at 225 °C for 30 min, dilution with water yields a solution with a hydrogen ion concentration of about 2.5 mol/liter that allows the use of stannous chloride-hydrazine sulfate as the reducing agent for phosphate color development. The color development and measurement may be carried out manually or with use of the AutoAnalyzer at an analysis rate of 40/hr. A coefficient of variation of about 7% and a standard deviation of 0.02 will be obtained with either the manual or semi-automated procedure.