title: Determination of polyhexamethylene biguanide hydrochloride using photometric colloidal titration with crystal violet as a color indicator.
abstract: A solution of polyhexamethylene biguanide hydrochloride (PHMB-HCl) was titrated with a standard solution of potassium poly(vinyl sulfate) (PVSK) using crystal violet (CV) as an photometric indicator cation. The end point was detected by a sharp absorbance change due to an abrupt decrease in the concentration of CV. A linear relationship between the concentration of PHMB-HCl and the end-point volume of the titrant existed in the concentration range from 2 to 10 × 10(-6) eq mol L(-1). Back-titration was based on adding an excess amount of PVSK to a sample solution containing CV, which was titrated with a standard solution of poly(diallyldimethylammonium chloride) (PDADMAC). The calibration curve of the PHMB-HCl concentration to the end point volume of the titrant was also linear in the concentration range from 2 to 8 × 10(-6) eq mol L(-1). Both photometric titrations were applied to the determination of PHMB-HCl in a few contact-lens detergents. Back-titration showed a clear end point, but direct titration showed an unclear end point. The results of the back-titration of PHMB-HCl were compared with the content registered in its labels.
authors.affiliation: Department of Applied Chemistry, Faculty of Engineering, Shibaura Institute of Technology, Toyosu, Koto, Tokyo 135-8548, Japan. masadome@sic.shibaura-it.ac.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Masadome
authors.forename: Takaaki
authors.initials: T
authors.lastname: Miyanishi
authors.forename: Keita
authors.initials: K
authors.lastname: Watanabe
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ueda
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Hattori
mesh_terms: D001645:Biguanides / Q000032:analysis*; D003102:Colloids / Q000737:chemistry; D004396:Coloring Agents / Q000737:chemistry*; D005840:Gentian Violet / Q000737:chemistry*; D007202:Indicators and Reagents / Q000737:chemistry; D010783:Photometry; D017186:Titrimetry / Q000379:methods*
chemical_list: D001645:Biguanides; D003102:Colloids; D004396:Coloring Agents; D007202:Indicators and Reagents; C031233:polihexanide; D005840:Gentian Violet