Unconjugated estriol in serum as measured by liquid chromatography with electrochemical detection, compared with radioimmunoassay.

Concentrations of unconjugated estriol in maternal serum or plasma increase throughout pregnancy, particularly during the third trimester. We present and discuss the results of a comparative study of unconjugated estriol as measured by a new "high-performance" liquid-chromatographic assay and by a conventional semiautomated radioimmunoassay procedure. In the new method, serum is extracted and chromatographed on a reversed-phase mu Bondapak-C8 column under radial compression. The estriol peak is detected with a glassy-carbon electrochemical detector. The chromatographic results (y) correlated well with the RIA results (x) for 105 samples from 45 pregnant women in their third trimester (y = 1.07x - 0.55 micrograms/L, r = 0.933), with no significant difference between the means of the two methods.