Abstract
SUMMARY: A chemical method for the estimation of oestriol, oestrone and oestradiol-17β in the blood of the pregnant woman and of the foetus is described. It is based on a method previously developed for urine and involves acid hydrolysis of whole blood, extraction of the phenolic fraction, methylation, chromatography on alumina columns and colorimetric measurement using a micro-modification of the Kober reaction. Kober-chromogenic impurities in the final extracts are derived from the procedure, not from the blood, and are eliminated by the spectrophotometric correction of Allen. The accuracy, precision, sensitivity and specificity of the method have been determined.