Solubility-based Separation and Purification of Long-Chain Chitin Oligosaccharides with an Organic-Water Mixed Solvent

A simple and rapid method for separation and purification of chitin oligosaccharides, (GlcNAc)_n, with n ≥ 5 is presented. A commercially available chitin oligosaccharides sample, consisting of (GlcNAc)_n with n = 1 - 7, was used as the starting material. Ten milligrams of the material was mixed with 100 μL of the 1 mol/L HCl. All the (GlcNAc)_n species were dissolved in the aqueous medium. The aqueous solution was mixed with 900 μL of EtOH; the mixture was centrifuged, and the supernatant was removed to obtain a precipitate. The precipitate was found to consist mainly of (GlcNAc)_n with n ≥ 5, indicating the significant difference in solubility between the short-chain (GlcNAc)_n species with n ≤ 3 and the longer ones. By the repetition of the operations, a high purity long-chain (GlcNAc)_n sample with n ≥ 5 could be prepared successfully. Since the long-chain (GlcNAc)_n species are known to have excellent elicitor activity, this sample would be useful in the study of plant pathology, as well as chitin and chitosan chemistry.

Adsorptive Voltammetry of 2-(5-Bromo-2-pyridyl)azo-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol on a Carbon Paste Electrode in the Presence of Organic Cations and Polycation

The adsorption of ion-association complexes on a carbon paste electrode (CPE) was investigated by cyclic voltammetry using an electroactive hydrophobic anion probe. The redox reactions of 2-(5-bromo-2-pyridyl)azo-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol (5-Br-PAPS), the analytical probe, were irreversible. The reduction of the azo group and the oxidation of the phenol were observed at -0.1 V and 0.9 V vs. SCE, respectively, in a 0.1 mol L(-1) H(2)SO(4) solution. The peak currents for the redox reaction increased with the concentration of the cationic surfactant and the accumulation time. The increase in the ratio of the peak current to the concentration of cationic surfactants was proportional to the hydrophobicity. The peak current for 5-Br-PAPS also increased when a polycation, polyhexamethylene biguanide hydrochloride, was added and was strongly dependent on the ionic strength and pH, in contrast to cationic surfactants.

Colloidal Titration of Aqueous Zirconium Solutions with Poly(vinyl sulfate) by Potentiometric Endpoint Detection Using a Toluidine Blue Selective Electrode

Zirconium oxy-salts were hydrolyzed to form positively charged polymer or cluster species in acidic solutions. The zirconium hydrolyzed polymer was found to react with a negatively charged polyelectrolyte, such as poly(vinyl sulfate), and to form a stoichiometric polyion complex. Thus, colloidal titration with poly(vinyl sulfate) was applied to measure the zirconium concentration in an acidic solution by using a Toluidine Blue selective plasticized poly(vinyl chloride) membrane electrode as a potentiometric end-point detecting device. The determination could be performed with 1% of the relative standard deviation. The colloidal titration stoichiometry at pH < or = 2 was one mol of zirconium per equivalent mol of poly(vinyl sulfate).

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.