CHEMILUMINESCENT ASSAY OF ALKALINE-PHOSPHATASE IN MILK

A highly sensitive and rapid chemiluminescent assay was developed to measure the concentration of alkaline phosphatase (ALP) in milk by monitoring the chemiluminescent signal from an ALP-triggerable dioxetane, the adamantyl-1,2-dioxetane phenyl phosphate (PPD). The emission of visible radiation was proportional to ALP concentration in the range from 0.05 to 10.4 mu kat/L at 25 degrees C with two different linear ranges 0-1.3 and 1.3-10.4 mu kat/L. The relative standard deviations within and between assays were less than 6%, and recoveries ranged from 0.92 to 1.05. The results agreed with those obtained by qualitative and quantitative absorption spectrometry for ALP. However the chemiluminescent method gave quantitative results without laborious solution and sample preparation and was more sensitive than absorption spectrometry (detection limit 0.03 mu kat/L and 0.1 mu kat/L, respectively). With undiluted PPD solution, a detection limit of 0.5 nkat/L was attained. ALP can also be detected by qualitative chemiluminescence with a photographic system.