Characterization of Norwegian natural organic matter: Size, diffusion coefficients, and electrophoretic mobilities

Eighteen Norwegian NOM samples were analyzed by AFM, TEM, FCS, and CE. The TEM and AFM gave complementary, but not identical, information regarding th e conformation of the NOM. A large majority of the material in ail samples appeared as points with a size of approximately 2 nm or less. FCS gave valu es for diffusion coefficients which were in the range 2.1-3.0 x 10(-10) m(2 ) s(-1). This corresponds to molecular diameters of between 1.6 and 2.0 nm, in reasonable agreement with both TEM and AFM, Electropherograms, using ab sorbance at 200 nm, were all dissimilar except for the Gjerstad and Helleru dmyra sample pairs, for which no major differences were observed. CE was al so carried out using both fluorescence (excitation at 325, 457, and 488 nm) and UV-absorbance (200, 210, 254, and 288 nm) detection on three of the NO M samples. The different modes of detection and wavelengths gave qualitativ ely similar electropherograms. Calculated EPMs of the major sample componen ts were in the range -2.0 to -5.0 10(-8) m(2) s(-1) V-1. (C) 1999 Elsevier Science Ltd.