Dissolved organic carbon chromatography

Determination of 63 cations by HR-ICPMS was done on filtered/acidified samples by Activation Laboratories Ltd., using a Finnegan Mat ELEMENT 2 instrument. Anions were determined by ion chromatography and Fe " and dissolved organic carbon (DOC) by spectrophotometry in USGS labs. 

Size exclusion chromatography (SEC) has been used to measure molecular weight (MW) distribution of humic substances (3, 6-9). Coupled with detection methods such as molecular fluorescence spectroscopy and dissolved organic carbon analysis (7), electrochemical detection (9), and atomic emission spectroscopy (5), SEC has been used extensively to study humic-metal complexes. A major disadvantage of SEC is that it does not provide adequate resolution for separating humic materials as they do not appear to be made up of distinct fractions with large differences in MW. 

Leenheer and Huffman (1976) designed a hydrophobic classification of dissolved organic carbon using resin adsorption as a means of fractionation. The procedure is based on adsorption chromatography onto XAD resins. Those organic substances that adsorb onto the resins with pH adjustment (low pH for acids and neutral pH for bases) are termed hydrophobic those organic substances that do not absorb are hydrophilic. Fulvic and humic acids are classified as hydrophobic substances. This classification procedure makes it possible to measure indirectly the amount of humic substances in water. A more detailed explanation of this procedure is presented by Leenheer (1981). 

Gloor, R., Leidner, H., Wuhrmann, K., and Fleischmann, T. H. (1981). Exclusion chromatography with carbon detection. A tool for further characterization of dissolved organic carbon. Water Res. 15, 457-462. 

Table 2. Dissolved organic species released from 300 g of crushed (0.5-2.0cm) Monterey Shale (MR-216) into 365 g of water after heating for 72 h at 330°C in 1-1 reactors with different surface compositions. Aliphatic acids were determined by ion exclusion chromatography and dissolved organic carbon (Org. C) was determined with a UV photooxidation carbon anayzer ... 

Huber S.A., Direct-injection size-exclusion chromatography (DISEC) of dissolved natural organic matter (NOM) using high-sensitiuvity organic carbon detection empiric chromatographic studies, (unpublished). 

Speciation calculations for the carbonate system using the alkalinity data and pH values after day 50 and plotted in Fig. 3, are consistent with C02(g) partial pressures ranging between 10" and lO atm. These values agree well with the values for carbon dioxide determined by gas chromatography of dissolved gases collected from water samples in boreholes at the site (Table 2). There is clearly a dominant source of carbon dioxide to the groundwater at the site, presumably microbial respiration or fermentation of organic carbon. 

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