Chemical Stability of Large Organic Molecule-Metal Complexes Dissolvedin Natural Water as Studied by Size Exclusion Chromatography/Inductively Coupled Plasma Mass Spectrometry.

摘要

The chemical stability of large organic molecule-metal complexes (LOMMC's) dissolved in pond water were investigated by a hyphenated system of size exclusion chromatography/UV absorption detection/inductively coupled palsma mass spectrometry (SEC/UV/ICP-MS) after ultrafiltration using a filter with a molecular permeation limit larger than 10000 Da.LOMMCs dissolvedint hepreconcentrated ond water sample were observed at the retention times corresponding to molecular weights larger than 300000 Da (Peak I) and that of 10000-50000 Da (Peak II) in the chromatograms measured by UV absorption andICP-MS.When the pH of the sample soultion was varied from 7.0 to 0.5 by adding the HNO-3 solution,the peak intensities of both Peak I and Peak II in these chromatograms decreased with the decrease in pH of the HNO-3 solution,the peak intensities of both Peak I and Peak II in these chromatograms decreased with the decrease in pH of thesample solution,the peak intensities of both Peak I and Peak II in these chromatograms decreased with the decrease in pH of the sample solution.These results indicate that LOMMCs were decomposed by addition of HNO-3.Peak I was rapidly decomposed below pH 4,while eak II was gradually decomposed over thepH range from 7.0 to 0.5.The decomposition curve of peak I was similar to the solubility characteristics of hydroxides of Fe and Al.On the other hand,that f Peak II suggested thedissociation s of metal complexes (Cu and Zn) with some biogenic organic molecules.It was concluded from these results that some colloidal particles of hydroxides of Fe and Al may be core materials ofLOMMCs for Peak I,while some metal complexes with biogenic protein-like compounds may be LOMMCs for Peak II.The possible models for LOMMCs in pond water were proposed as "a strig-ball model" which might interpret as theremoval and preservation mechanisms for trace elements in natural water.