Horseradish peroxidase sol–gel immobilized for chemiluminescence measurements of alkaline-phosphatase activity

2-Naphthyl phosphate is a pro-enhancer of the luminol–H2O2–horseradish peroxidase reaction. Alkaline-phosphatase hydrolyses the phosphate group and produces 2-naphthol. This compound is an enhancer of the chemiluminescence (CL) reaction. The influence of 2-naphthyl phosphate and the incubation time on the chemiluminescence reaction, have been studied. The horseradish peroxidase (HRP) was immobilized in a sol–gel matrix, obtaining a biosensor for alkaline-phosphatase. The relative standard deviations using free HRP in solution and the immobilized one were 3.2 (n=4) and 9.3% (n=3), respectively. The detection limits for alkaline-phosphatase using free and immobilized HRP were 128 and 106 μU/ml, respectively.