Determination of cholinesterase in blood serum using a benzoate-selective membrane electrode made with heptyl-4-trifluoroacetylbenzoate neutral carrier

A benzoate-selective membrane electrode made with heptyl-4-trifluoroacetylbenzoate as a neutral carrier was successfully used to determine cholinesterase activity in blood serum, by detecting benzoic acid formed by the enzymatic hydrolysis of benzoylcholine with cholinesterase. The electrode decreased interference by chloride much more effectively than a previous benzoate electrode made with the ion exchanger methyltridodecylammonium chloride, and facilitated the sensitive assay of benzoate (0.2–50 mM) in the presence of serum. The detection limit of benzoate in physiological saline was 100 μM. The present procedure compares favorably with an established colorimetric determination of cholinesterase, being simple, rapid and economical.