Determination of Polyhexamethylene Biguanide Utilizing a Glucose Oxidase Enzymatic Reaction

Polyhexamethylene biguanide (PHMB) is a cationic disinfectant widely used for personal-care products and for sanitizers in swimming pools. This paper describes a promotion effect of PHMB on a glucose oxidase (GOx) enzymatic reaction with ferricyanide ion and its analytical application. The promotion effect arose from a polyion complex formation between polycationic PHMB and polyanionic GOx. The promoted GOx reaction was analyzed by Michaelis–Menten equation, and the Michalis constant and catalytic constant were estimated to be 240 μM and 31 s−1, respectively. Utilizing the promotion effect, PHMB was successfully determined in the range of 0.05 to 0.40 ppm, and the detection limit was calculated to be 0.027 ppm. The visual detection and semi-determination of PHMB with the same concentration level were also possible. As an application, the method was applied to the determination of PHMB in a contact lens detergent and its model solution.