Direct immunoassay of estriol in pregnancy serum by capillary electrophoresis with laser-induced fluorescence detector

A simple and sensitive capillary electrophoretic immunoassay (CEIA) was described for the determination of estriol (E3) in pregnant womenʹs serum. The method was based on the competitive reaction of fluorescein-labeled E3 antigen and E3 with limited amounts of monoclonal antibody. The addition of the thermally reversible hydrogel, poly-N-iso propylacrylamide (pNIPA) in the buffer serving as a replaceable packing material, improved the reproducibility of the method. With laser-induced fluorescence detector (LIF), this method can be applied to determine E3 at concentrations lower to 31.6 pg ml−1. Recoveries from human steroid-free serum matrix were greater than 94% with relative standard deviation (R.S.D.) values less than 3.5%. Serum E3 levels of ten normal pregnant women were measured at the range of 10.2–15.6 ng ml−1.