Determination of placental estriol in urine by gas-liquid chromatography, with equilenin as internal standard.

Placental estriol in urine can be determined by rapid enzymatic hydrolysis, extraction with neutral XAD-2 resin, and quantitation by gas-liquid chromatography, with equilenin as the internal standard. Glucose, methenamine mandelate, hydrochlorothiazide, phenolphthalein, or salicylate do not interfere. Analytical recovery of estriol added to urine was 92-108%. Day-to-day precison (CV), established by 15 repilicate analyses at a mean concentration of 21.3 mg/liter, was 6.6%.