Department of Chemistry, Northeastern University, Shenyang, China.
Anal Chim Acta. 2011 Jul 18;698(1-2):27-35. doi: 10.1016/j.aca.2011.04.056. Epub 2011 May 6.
Cellulose acetate dialysis membrane (CDM) has been used in the diffusive gradients in thin films (DGT) technique, where accurate diffusion coefficients are essential for the assessment of the concentrations of labile metal in solution. Effective concentration difference model (ECDM), based on the assumption that the effective diffusion coefficient of metal ion in the dialysis membrane is determined by the effective concentration difference (ΔC(e)) across the dialysis membrane, is proposed and applied to study the effect of ionic strength, binding agent, ligands and Donnan potential on the effective diffusion coefficient. The effective diffusion coefficients of Cd(2+) through the dialysis membrane immersed in receptor solutions with binding agent were almost the same as those in receptor solutions without binding agent at higher ionic strengths (0.01-1 M) but much higher than those at lower ionic strengths (0.001-0.0001 M). The effective diffusion coefficients of Cd(2+) through the dialysis membrane immersed in deionized water receptor solutions with binding agent were not significantly different from those in synthetic receptor solutions (receptor solutions with various ionic strengths) with binding agent. The DGT-labile fractions were measured in synthetic solutions and natural waters, which indicated that the effective diffusion coefficients, through the dialysis membrane immersed in the deionized water solution with binding agent as receptor solution and in the spiked natural water as source solution, were more suitable for DGT application.
醋酸纤维素透析膜（CDM）已应用于扩散梯度薄膜技术（DGT）中，在该技术中，准确的扩散系数对于评估溶液中可利用金属的浓度至关重要。有效浓度差模型（ECDM）是基于金属离子在透析膜中的有效扩散系数由透析膜两侧的有效浓度差（ΔC(e)）决定的假设提出的，并应用于研究离子强度、结合剂、配体和Donnan 势能对有效扩散系数的影响。在较高离子强度（0.01-1 M）下，透析膜在含结合剂的受体溶液中，Cd(2+)的有效扩散系数与不含结合剂的受体溶液中的扩散系数几乎相同，但在较低离子强度（0.001-0.0001 M）下，Cd(2+)的有效扩散系数比在较高离子强度下高得多。在含结合剂的去离子水受体溶液中，透析膜的有效扩散系数与含结合剂的合成受体溶液（不同离子强度的受体溶液）中的扩散系数没有显著差异。在合成溶液和天然水中测量了 DGT-可利用分数，这表明在以去离子水加结合剂为受体溶液的透析膜中以及以添加天然水为源溶液的透析膜中，有效扩散系数更适合于 DGT 的应用。
