INTERCOMPARISONS OF SOME NEW APPROACHES FOR INVESTIGATING THE MOLECULAR WEIGHT DISTRIBUTION OF DISSOLVED ORGANIC MATTER

摘要

Molecular weight is an important piece of information in the identification and study of organic molecules.Many analytical techniques including vapor-pressure osmometry(VPO)(Aiken and Malcolm,1987),flow field-flow fractionation(Beckett et al.,1987),ultrafiltration(Tadanier et al.,2000),multi-angle laser light scattering(Wagoner et al.,1997)and high-pressure size exclusion chromatography(HPSEC)(Chin et al.,1994)have been employed to obtain the molecular weight distribution of DOM.However,the values obtained highly depend on the employed methods.The number average molecular weights(M_n)of the Suwannee River DOM(fulvic acids in some cases)reported in previous studies have been shown to vary from 800 to 15,000.In this study,three new approaches to molecular weight determinations are employed and compared with size exclusion chromatography.These include 1)electrospray ionization mass spectrometry(ESI-MS),2)desorption ionization on silicon chip mass spectrometry(DIOS-MS),and 3)diffusion ordered spectroscopy(DOSY).