Standard pH values in non-aqueous mobile phases used in reversed-phase liquid chromatography

✍ Scribed by J. Barbosa; V. Sanz-Nebot

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 488 KB
• Volume: 283
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(93)85238-f

✦ Synopsis

Standard pH, values for three reference buffer solutions (0.05 mol kg' potassium dihydrogencitrate; 0.1 mol I-' acetic acid + 0.1 mol I-' sodium acetate: 0.03043 mol kg' disodium hydrogenphosphate + 0.008695 mol kg-' potassium dihydrogenphosphate) in 10, 30, 40, 50 and 70% (w/w) acetonitrile-water mixtures at 298.15 K were determined from e.m.f. measurements of the reversible cell Pt/Ag/AgCl/standard buffer + KCI, in acetonitrilewater/glass electrode. In order to obtain pH, values in each of the unlimited number of possible acetonitrile-water mixtures, pH, values were correlated with mole fraction, % (w/w) and % (v/v) of acetonitrile in solvent mixtures and the methodology of linear solvation energy relationship, based on the Kamlet-Taft multiparametric scales, was applied and pH, data were correlated with rr*, a and p solvatochromic parameters of the acetonitrile-water mixtures.

Keyworuk Liquid chromatography; Acetonitrile; pH; Standard pH values

Mixed aqueous-organic solvents are widely used in chemistry to enhance the reactivities, solubilities, biological absorption properties and chromatographic properties of a wide variety of chemical substances. As in aqueous solutions, the pH of the solvent will be affected by solutes and its control will often be necessary in order to obtain optimum chemical results. The solvent system chosen in this study was acetonitrile-water because of its wide use in reversed-phase liquid chromatography (RPLC).

Many different methods have been devised for optimizing the selectivity of chromatographic separations [l-3]. Usually, the methods focus on the optimization of the mobile phase composition, i.e., on the concentrations of water and organic