A specific method for the determination of millimicrogram amounts of urinary oestrone.

1. A new combined radioactivity-fluorescence method is described for urinary oestrone, which involves acid hydrolysis, extraction and purification of the phenolic fraction, saponification, a Girard T separation and alumina chromatography of acetylated oestrone. 2. Sulphuric acid fluorescence is used for quantitation and specificity is achieved by the addition of tritiated oestrone to the urine hydrolysate. This radioactive tracer functions both as an internal corrector for purification losses and enables the demonstration of constant specific activity through the oestrone peaks to act as an index of specificity in each determination. 3. By using one-fifth of a 24hr. urine sample, 1mug. of urinary oestrone/24hr. can be determined with an accuracy of +/-4%. Fluorescence emission spectra from processed urine samples are identical with that of authentic oestrone acetate. 4. The advantages of the method are its high sensitivity and specificity, which is achieved with relative convenience.