FERROCENYLETHYL PHOSPHATE - AN IMPROVED SUBSTRATE FOR THE DETECTION OF ALKALINE-PHOSPHATASE BY CATHODIC STRIPPING ION-EXCHANGE VOLTAMMETRY - APPLICATION TO THE ELECTROCHEMICAL ENZYME AFFINITY ASSAY OF AVIDIN
B. Limoges et C. Degrand, FERROCENYLETHYL PHOSPHATE - AN IMPROVED SUBSTRATE FOR THE DETECTION OF ALKALINE-PHOSPHATASE BY CATHODIC STRIPPING ION-EXCHANGE VOLTAMMETRY - APPLICATION TO THE ELECTROCHEMICAL ENZYME AFFINITY ASSAY OF AVIDIN, Analytical chemistry, 68(23), 1996, pp. 4141-4148
The ferrocenylethyl phosphate disodium Salt was synthesized and used a
s a new substrate for alkaline phosphatase (AP). The enzyme-generated
ferrocennethanol was selectively and sensitively detected at a Nafion
film-coated electrode by anodic preconcentration of the ferricinium sa
lt, followed by cyclic voltammetry, The accumulated ferricinium units
could he expelled from the polymer film in their neutral form by catho
dic stripping, and so the nafion-modified electrode could be reused fo
r more than 10 measurements with a standard deviation less than 3%. Va
lues of 0.75 mM for the Michaelis constant and 1.42 mu mol s(-1) (mg o
f protein)(-1) for the maximal velocity were found. The regenerable Na
fion-coated electrode was employed for the indirect detection of AP do
wn to 2 x 10(-12) M and for the noncompetitive heterogeneous enzyme as
say of avidin, whose detection limit was 5 x 10(-12) M.