Combination of asymmetric flow field-flow fractionation (AF4) and total-reflexion X-ray fluorescence analysis (TXRF) for determination of heavy metals associated with colloidal humic substances.
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).
Exner
A
A
Institute for Hydrochemistry, Technical University of Munich, Germany.
Theisen
M
M
Panne
U
U
Niessner
R
R
D002021:Buffers; D002138:Calibration; D003102:Colloids; D004867:Equipment Design; D006812:Humic Substances / Q000032:analysis / Q000737:chemistry*; D019216:Metals, Heavy / Q000032:analysis*; D013052:Spectrometry, X-Ray Emission / Q000295:instrumentation / Q000379:methods
D002021:Buffers; D003102:Colloids; D006812:Humic Substances; D019216:Metals, Heavy