Chemiluminescence assay of alkaline phosphatase using cortisol-21 -phosphate as substrate and its application to enzyme immunoassays

A method is described for the highly sensitive chemiluminescence (CL) assay for alkaline phosphatase (ALP) using cortisol-21-phosphate (cortisol-21-P) as substrate and lucigenin as CL reagent; it is applied to an enzyme immunoassay (EIA) for human chorionic gonadotropin (hCG), human growth hormone (hGH), α-fetoprotein (AFP) and estradiol (E2). The detection limit for ALP was 8.75 × 10−20mol/assay, and the average coefficient of variation (n = 11) over the calibration range (3.55 × 10−15–7.1 × 10−10mol l−1) was 6.4%. In EIA for hCG, hGH, AFP and E2, the detection limits were 0.008 mIU ml−1. 10, 40 and 0.25 pg ml−1, respectively.