Ian J. Bradshaw

The rapid quantitative determination of alginates by poly(hexamethylenebiguanidinium chloride) complexation in industrial liquors extracted from brown seaweed

Abstract Further development of the poly(hexamethylenebiguanidinium chloride) assay method previously reported by these authors for the determination of alginates has resulted in a rapid procedure to determine this polysaccharide in liquors obtained by alkali extraction of brown seaweeds. The method involves neutralisation of the liquor followed by a simple alginate precipitation procedure employing the organic cation poly(hexamethylenebiguanidinium chloride) which possesses a UV absorption at 235 nm and can therefore be used in the quantitative step of the assay. Results produced by the assay for determination of alginate in liquors are in good agreement with another recognised method. The method is insensitive to the presence of numerous substances in the liquors in addition to alginate. In contrast to many other existing methods, alginate materials with various d -mannuronic acid/ l -guluronic acid ratios show essentially identical responses to the assay.

Reaction of PHMBH+Cl− with acidic polysaccharides, and its application to the purification of xanthan gum

Abstract Poly(iminocarbonimidoyliminocarbonimidoylimino-1,6-hexanediyl hydrochloride) [PHMBH+Cl−] reacts with acidic polysaccharides to form white, insoluble salts. The PHMBH+ salts of sulphated polysaccharides can only be dissociated at or below pH 0·2. The salts of polysaccharides containing only carboxylate groups as their acidic functions are dissociated at or below pH 1·6, and by strong electrolytes above a critical electrolyte concentration. The acidic polysaccharide xanthan may be recovered from a dispersion of its PHMBH+ salt in aqueous potassium chloride by treatment with 2-propanol. This forms the basis of a method for the recovery of xanthan, in purified form, from Xanthomonas campestris fermentation broths. The reaction of PHMBH+Cl− with nucleic acids and proteins is also discussed.

The isolation of xanthan gum from fermentations of Xanthomonas campestris by complexation with quaternary ammonium salts

Abstract A comparison of the use of the quaternary ammonium salts, cetyltrimethylammonium bromide (CTAB) and the commercial mixture Cetavlon, for the isolation of xanthan gum from fermentations of Xanthomonas campestris indicated that the former was the more efficient complexating agent. Although in both cases more than the stoichiometric requirement was necessary to achieve quantitative recovery of the polysaccharide, CTAB left only 1·7% material in the supernatant from the precipitation of xanthan gum compared to 15% left by Cetavlon. This is congruent with the view that the efficiency of quaternary ammonium salts increases with increased paraffin chain length. An assessment of the use of Cetavlon for the isolation of xanthan gum in a recycle procedure showed that an 11·5% loss of precipitant per cycle occurred. In the procedure, the xanthan gum was precipitated as the purified K + salt from a dispersion of its quaternary ammonium complex in 2-propanol. Concentration of the 2-propanol wash permitted recovery of the quaternary ammonium salt.

The assay of acidic polysaccharides in solution with poly(hexamethylenebiguanidinium chloride)

Abstract The poly(hexamethylenbiguanidinium chloride) [PHMBH + Cl − ] assay method, developed originally for the determination of sodium alginate in solution (0.01–0.5%), has been applied to a range of other acidic polysaccharides. Response in the assay is dependent upon the ratio of acidic groups to monosaccharide, which can be altered for polysaccharides with differing anionic charge densities. When the charge density is low, as with highly esterified propylene glycol alginates, the response can be increased by complexation of the polymer with borate ions which increases the negative charge. The nature of the response allows the determination of the extent of esterification up to ∼70% in propylene glycol alginates. The method is suitable for samples of low molecular weight and is therefore more reliable than other assays for acidic polysaccharides which involve a precipitation step. The simplicity, rapidity, and reliability of the method make it suitable for both carboxylated and sulphated polysaccharides.

A comparison of the poly(hexamethylenebiguanidinium chloride) assay and a neutral equivalent method for the determination of alginates in industrial liquors extracted from brown seaweed

Abstract The poly(hexamethylenebiguanidinium chloride) assay and a neutral equivalent method have been used to estimate the sodium alginate content of industrial liquors extracted from brown seaweed. With the liquor samples examined, agreement to within 5% was achieved with the two methods under defined alginate concentration conditions. Statistical evaluation of the data using a paired comparison t-test has shown that a difference of only 0·10±0·05 can be expected with 95% confidence, between the two methods in the analysis of liquor samples with sodium alginate contents in the range 2·00–3·83 mg ml−1. In the majority of cases the PHMBH+ Cl− method gave a slightly higher estimate that the neutral equivalent method. Consideration of the practical aspects of the two alternative methods allows this difference to be explained. The simplicity of the PHMBH+ Cl− assay renders it suitable for the rapid screening of large numbers of alginate samples.

Outcomes and Benefits of a Knowledge Transfer Partnership in Chemical Science

Knowledge Transfer Partnership (KTP) is a UK initiative to enable companies to benefit from the knowledge and skills within Universities. A recent chemically based KTP between Liverpool John Moores University and Salt Union Ltd provided a range of benefits to the University, Company and Associate. The transfer of knowledge to the Company has resulted in the development of a research capability, optimised products and an increase in profits. The Associate has gained commercial experience, enhanced qualifications and training, and at the culmination of the funded programme, was appointed within the Company at managerial level. The academic staff from the knowledge base partner have developed their research standing, gained commercial awareness and enhanced their teaching with industrial case studies and projects.