Determination of biguanide groups in polyhexamethylene biguanide hydrochloride by titrimetric methods.

The biguanide concentration of polyhexamethylene biguanide hydrochloride (PHMB-HCl) was measured by non-aqueous titration with HClO4, argentometric titration, the Kjeldhal method, and colloidal titration. The summation value of non-aqueous titration and argentometric titration corresponded to two titrable nitrogens in five nitrogens per one unit of PHMB-HCl, and consisted with the result of the Kjeldhal method to the five nitrogens. The colloidal titration of PHMB-HCl at pH 2.05 was equal to that with the two nitrogens. The relative standard deviations of non-aqueous titration, argentometric titration, the Kjeldhal method, and colloidal titration were 0.50% for 8 runs, 0.13% for 7 runs, 3.61% for 6 runs, and 0.69% for 6 runs, respectively.