A rapid method for the assay of alginates in solution using polyhexamethylenebiguanidinium chloride

A rapid method for the quantitative assay of alginate in solution over a wide concentration range (0.01–0.5 percent) has been developed using the polymetric cation poly(hexamethylenebiguandinium chloride) [PHMBH+Cl−]. The procedure consists of the addition of a known excess amount of PHMBH+Cl− to alginate solutions to precipitate the sample quantitatively and therafter measuring the u.v. absorption of residual PHMBH+C1− in the supernatant. The working range of the assay can be altered by simply adjusting the excess quantity of PHMBH+Cl− which is added during the assay. Assay response is easily reproducible and insensitive to variation in salt concentration (up to 2.5 per cent), pH (5.5–7.6) and temperature (10–60°C). The PHMBH+Cl− method shows good agreement with another recognised method for the assay of alginate solutions. The simplicity of this new method and the short time required to perform it, enhances its suitability as a quick analytical procedure for alginates. Preliminary evidence suggests that assay response is independent of the D-mannuronic acid/L-guluronic acid ratio of alginate.