Fournier Agathe C, Shafran Kirill L, Perry Carole C
School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, UK.
Anal Chim Acta. 2008 Jan 21;607(1):61-73. doi: 10.1016/j.aca.2007.11.026. Epub 2007 Nov 21.
The 'formal' hydrolysis ratio (h = C(OH-)added/C(Al)total) of hydrolysed aluminium-ions is an important parameter required for the exhaustive and quantitative speciation-fractionation of aluminium in aqueous solutions. This paper describes a potentiometric method for determination of the formal hydrolysis ratio based on an automated alkaline titration procedure. The method uses the point of precipitation of aluminium hydroxide as a reference (h = 3.0) in order to calculate the initial formal hydrolysis ratio of hydrolysed aluminium-ion solutions. Several solutions of pure hydrolytic species including aluminium monomers (AlCl3), Al13 polynuclear cluster ([Al13O4(OH)24(H2O)12]7+), Al30 polynuclear cluster ([Al30O8(OH)56(H2O)26]18+) and a suspension of nanoparticulate aluminium hydroxide have been used as 'reference standards' to validate the proposed potentiometric method. Other important variables in the potentiometric determination of the hydrolysis ratio have also been optimised including the concentration of aluminium and the type and strength of alkali (Trizma-base, NH3, NaHCO3, Na2CO3 and KOH). The results of the potentiometric analysis have been cross-verified by quantitative 27Al solution nuclear magnetic resonance (27Al NMR) measurements. The 'formal' hydrolysis ratio of a commercial basic aluminium chloride has been measured as an example of a practical application of the developed technique.
水解铝离子的“形式”水解率（h = 添加的C(OH⁻)/总C(Al)）是水溶液中铝进行详尽且定量的形态-分级分析所需的重要参数。本文描述了一种基于自动碱滴定程序测定形式水解率的电位滴定法。该方法以氢氧化铝沉淀点为参考（h = 3.0）来计算水解铝离子溶液的初始形式水解率。几种纯水解物种的溶液，包括铝单体（AlCl₃）、Al₁₃多核簇（[Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺）、Al₃₀多核簇（[Al₃₀O₈(OH)₅₆(H₂O)₂₆]¹⁸⁺）以及纳米颗粒氢氧化铝悬浮液，已被用作“参考标准”来验证所提出的电位滴定法。电位滴定法测定水解率中的其他重要变量也已得到优化，包括铝的浓度以及碱的类型和强度（三（羟甲基）氨基甲烷碱、NH₃、NaHCO₃、Na₂CO₃和KOH）。电位分析结果已通过定量²⁷Al溶液核磁共振（²⁷Al NMR）测量进行交叉验证。作为所开发技术实际应用的一个例子，已测定了一种市售碱式氯化铝的“形式”水解率。
