Solubility products for aminocarboxylate ligands: determination, validation and speciation uses

A method combining glass electrode potentiometry and computer simulation of speciation is described and used to determine the solubility product for S,S′-ethylenediamine disuccinate (EDDS) (also known as ethylenediiminodibutanedioic acid). This previously unpublished constant is validated by re-measuring K_sp for isomeric EDTA⁴⁻·H₄⁺ and by a linear free energy relationship. For EDDS⁴⁻·H₄⁺, log K_sp=−25.75±0.30.     

高效液相色谱法测定生物转化反应液中N,N'-乙二胺二琥珀酸

建立了高效液相色谱测定生物转化反应液中N,N'-乙二胺二琥珀酸（EDDS）含量的分析方法。采用InertSustain AQ-C₁₈色谱柱（250 mm×4.6 mm,5 μm）,以体积分数25%的甲醇水溶液（含有1.0 g/L一水乙酸铜、2.0 g/L四丁基氢氧化铵,以磷酸调节pH至2.80）为流动相,流速为1.0 mL/min,柱温为30℃,进样量为20 μL,检测波长为254 nm。该方法可在8 min内分离EDDS及其生物合成相关物质（苹果酸、柠檬酸、乙二胺四乙酸（EDTA）和富马酸）,且峰形良好。EDDS在0.06~0.6 g/L范围内线性线性关系良好（相关系数（r）为0.9995）,平均回收率为100.39%（n=9,RSD=1.15%）。EDDS生物合成反应液中EDDS含量为0.25 g/L,大部分底物被转化为苹果酸（36.56 g/L）;而EDDS的水解反应中富马酸产生较少,形成了3.05 g/L的苹果酸。该方法简便快速,灵敏可靠,适用于EDDS生物合成的研究。     

Protocol for Extraction and Determination of Cr(VI) in Solid Materials with a High Cr(III)/Cr(VI) Ratio Using EDDS as a Leaching Agent for Cr(VI) and a Masking Agent for Cr(III)

A sensitive and selective protocol for the extraction of all forms of Cr(VI) from solid materials followed by determination by catalytic adsorptive stripping voltammetry has been elaborated. Cr(VI) was leached to a solution with 0.2 mol L^?1 (NH₄)₂SO₄/NH₄OH+0.1 mol L^?1 EDDS (pH 9.5) and simultaneously Cr(III) was transferred to a nonactive electrochemical complex with EDDS. The method allows for Cr(VI) determination in solid samples containing even a 1000–2000 fold excess of extractable Cr(III) without its noticeable influence. The effects of several experimental variables such as the composition and pH of the extractant, the time and temperature of the solid sample mixing with the extractant were studied. At the optimized conditions more than 95% of total Cr(VI) recoveries from solid samples were achieved. The validation of the proposed procedure was carried out by Cr(VI) determination in certified reference material CRM 019 Ash, spiked and unspiked with Cr(III), and by comparing the obtained results with those obtained using other common extraction procedures.     

Complexation of some environmentally friendly carboxylic acid ligands with La3+ ion in aqueous solution

In search for environmentally friendly metal chelating ligands for industrial applications, protonation, and complex-formation equilibria of iminodisuccinic acid (IDS), 3-hydroxy-2,2′ -iminodisuccinic acid (HIDS), N,N′-ethylenediaminedisuccinic acid (EDDS), and oxydisuccinic acid (ODS) with La³⁺ in aqueous 0.1?mol?L^?1 NaCl solution were studied at 25°C by potentiometric titration. The model for complexation and the stability constants of the different complexes were determined using the computer program SUPERQUAD. Complex formation was dominated by stable LaL^? complexes for all tested ligands.