Exner A, Theisen M, Panne U, Niessner R
Institute for Hydrochemistry, Technical University of Munich, Germany.
Fresenius J Anal Chem. 2000 Feb;366(3):254-9. doi: 10.1007/s002160050050.
To assess the structural variability of colloidal humic substances and the associated heavy metals an off-line coupling of asymmetric flow field-flow fractionation (AF4) with total-reflection X-ray fluorescence analysis (TXRF) is presented. AF4 allows a rather gentle separation of colloids with a minimum of interference and artifacts as no shear forces, drying, or interactions with a stationary phase are involved. After a calibration with suitable polymer particles of known molecular weight, the molecular weight distribution of colloidal humic substances between 1 and 10(3) kDa can be assessed with AF4. The combination with TXRF permits a simultaneous multielement analysis after preconcentration of samples on the AF4 channel using an optimized buffer. The analysis of seepage and sewage water sample and a sewage sludge sample yielded continuous distributions of the molecular weight and the associated heavy metals. The potential of AF4-TXRF coupling for the study of metal ion exchange equilibria with colloids was demonstrated by spiking seepage water with various heavy metals and subsequent AF4-TXRF analysis of the heavy metals bound to the colloidal fraction (Cu, Cr, Zn, Ni, Co).
为了评估胶体腐殖质和相关重金属的结构变异性，本文提出了一种非对称流场流分级（AF4）与全反射X射线荧光分析（TXRF）的离线联用方法。AF4能够以最小的干扰和伪像对胶体进行较为温和的分离，因为它不涉及剪切力、干燥或与固定相的相互作用。在用已知分子量的合适聚合物颗粒进行校准后，AF4可以评估1至10³ kDa之间胶体腐殖质的分子量分布。与TXRF联用可以在使用优化缓冲液将样品预浓缩在AF4通道上后进行同步多元素分析。对渗流水、污水样品和污水污泥样品的分析得出了分子量和相关重金属的连续分布。通过向渗流水添加各种重金属并随后对结合在胶体部分的重金属（铜、铬、锌、镍、钴）进行AF4-TXRF分析，证明了AF4-TXRF联用在研究金属离子与胶体交换平衡方面的潜力。
