Shaking polystyrene beads during coating with antibody: effect on the precision profile of enzyme immunoassay of triiodothyronine.

Evaluating an enzyme immunoassay (EIA) procedure based on antibody coated on solid-phase materials for assay of triiodothyronine (T3) (1), we observed a considerable improvement in the precision of this assay when the antibody coating on solid-phase matrix was carried out with shaking. In the EIA procedure, the coated beads are incubated with 30 pg of horseradish peroxidase-labeled T3 and T3 standards in concentrations ranging from 0.25 to 4 pg/L. After 2 h, the beads are washed and kept in contact with 1 mL of substrate/chromogen solution containing H202 and o-phenylenediamine. The reaction is stopped by addition of 4 molfL H2S04 after 40 mm, and the absorbance is measured. For this study, we performed the assay in 10 replicates and constructed precision profiles (2). Rabbit antiserum toT3 was absorbed