title: Studies on adsorption characteristics and mechanism of adsorption of chlorhexidine mainly by carbon black.
abstract: The extent of adsorption of chlorhexidine to carbon black and sanitary cotton was determined by measuring the amounts of chlorhexidine adsorbed to carbon black or sanitary cotton from the chlorhexidine solution containing specific amount of carbon black or sanitary cotton. As another comparative antiseptic example of adsorption phenomena, adsorption of acrinol to sanitary cotton was also studied. The specific surface area of carbon black was measured by the BET method of adsorption isotherm. The pattern of adsorption of chlorhexidine to carbon black was temperature-dependent Langmuir isotherms, and the amounts adsorbed increased as the temperature was raised. Since chlorhexidine, whose pKa's are 2.2 and 10.3, is considered to exist in aqueous solution as the di-cation, an ion-ion interaction should be formed between protonated biguanide and anionic portions of carbon black or sanitary cotton. The chlorophenyl and hexane moieties interact with hydrophobic portions of carbon black or sanitary cotton. The perturbation experiment conducted on this interaction system showed that the nature of interaction was irreversible. The enthalpy change calculated from Langmuir constants was small, indicating the existence of ion-ion interaction. The entropy values, 27.4 to 28.2 e.u. obtained in this system, suggested that the hydration shells of the ions were rather tightly bound. The area occupied by a chlorhexidine molecule, 548 (A)(2), was twice greater than the projection area, 276 (A)(2), suggesting that chlorhexidine was adsorbed in such a way that each molecule is sufficiently well spaced.
authors.affiliation: Faculty of Pharmaceutical Sciences, Kobe Gakuin University, 518 Arise, Ikawadani-cho, Nishi-ku, Kobe 651-2180, Japan. akaho@pharm.kobegakuin.ac.jp
authors.forename: E
authors.initials: E
authors.lastname: Akaho
authors.forename: Y
authors.initials: Y
authors.lastname: Fukumori
mesh_terms: D000327:Adsorption; D000891:Anti-Infective Agents, Local / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D002710:Chlorhexidine / Q000737:chemistry*; D003368:Gossypium; D013696:Temperature
chemical_list: D000891:Anti-Infective Agents, Local; D002244:Carbon; D002710:Chlorhexidine