Aromatic plus olefinic carbon content

A method was devised for estimating aromatic plus olefinic carbon content and total ring content. H NMR spectral data are used to estimate aromatic plus olefinic carbon content, and 13C NMR and NMR spectral data are combined with elemental carbon, hydrogen, and ash analyses to determine ring content. 

Fulvic acid from the Suwannee River was used to calibrate peak-height ratios for aromatic carbon content. The application of this method to fulvic acid samples with known aromatic plus olefinic carbon content from various environments is shown in Table II. Aromatic plus olefinic carbon percentages calculated by the peak-height ratio method using lH NMR data closely agree with these percentages computed from 13C NMR data, with the exception of the Big Soda Lake samples. 

Table III H-NMR Spectral Peak-Height Ratios and Aromatic Plus Olefinic Carbon Contents of Dissolved Humic Substances...

Although the peak 5 1 ratio indicating aromatic plus olefinic carbon content appeared typical, the peak 2 1 and 4 5 ratios were the lowest for... 

Table II. Data Used To Determine Aromatic Plus Olefinic Carbon Percentage and Ring Content of Fulvic Acids...

H NMR data from these seven sites are presented by spectral peak-height ratios in Table III. The sites were listed in order of increasing aromatic plus olefinic carbon percentages. Fulvic acids from all the lake samples are much lower in aromatic plus oleflnic carbon content than those from river samples. These results confirm the hypothesis that autothonous inputs result in dissolved humic substances that have a low aromatic plus oleflnic carbon content. The lake samples also are lower in the ratios of peak 2 (carboxylated chains and aliphatic ketones), peak 3 (carbohydrates), and peak 4 (phenolic tannins and lignins) to peak 1 (branched methyl groups and alicyclic ali-phatics) than are the river samples. 

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