Elemental Analysis and Structure

The elemental composition of natural organics varies from source to source and is different for NOM, FA, and HA. Values published for Suwannee River Reference FA and HA, DOM and Aldrich HA are shown in Table 2.2. For NOM, or DOM in this case, the analysis is more complex due to a generally very high ash content. The DOM was extracted with RO and contains a higher proportion of polar aliphatic substances (e.g. carbohydrates, proteinaqueous compounds). This was expected, as XAD 

The stmctures of HA and FA are not yet determined. A combination of many techniques is required to determine the structure of HSs. Schulten et al. have employed p) Tolysis-gas chromatography with electron impact and field ionisation mass spectrometry (Py-GC/MS), in-source pyrolysis-field ionisation mass spectrometry (Py-FIMS), CP/MS NMR, oxidative and reductive degradation, colloid chemical methods, and electron microscopy to develop a carbon network structure for soil HS (Schulten (1994), Schulten and Schnitzer (1993)). The elemental composition of FLA was C3()8H32s09oN5 fot MW of 5540 Da. This indicates of the complexity of such compounds and the extensive techniques required. If carbohydrates or proteinaceous materials are bonded covalently with HA, %C content decreases and %0 content increases. 

Aqueous humics are generally smaller. Reddy et al. (1989) estimated an elemental composition of C34.3H ,3.iOi9.2 fot FA of MW 750. Leenheer et al. (1989) proposed three structural models for FA but suggested that a large diversity of structures is likely to exist. 

While such analysis are not the subject of this study, it is important to note that the structure of a compound does influence retendon by membranes and the conformation in the boundary layer which influences flux. 

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Ion chromatography plays a prominent role in the characterization of pharmaceutically relevant compounds predominantly in the early stages of research. This includes the trace analysis of impurities and metabolites, the elemental analysis and structural elucidation of counter ions. These counter ions are often inorganic anions such as chloride and bromide or organic acids such as acetate, methyl sulfate, and trifluoroacetate. 

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