Chromatographable organic carbon

A way out of the dilemma is the determination of the molecular size distribution of the chromatographable organic carbon (COC) as it is offered from size exclusion chromatography (SEC) equipped with an organic carbon (OC) detection system. 

Figure 10.3. Size exclusion chromatogram obtained by UV and OC detection (SEC/UV-DOC) for a river sample (river Neckar, Heidelberg, 22.03.2007, DOC = 2.3 mg liter 1, chromatographable organic carbon (COC = 75%). Column TSK HW50S (250 x 20mm). Eluent phosphate buffer, 26.8mmol liter 1, UV (254nm) and organic carbon (OC) detection, exclusion volume V0, permeation volume Vp).

Critical Coagulation Concentration Chromatographable Organic Carbon Chloral Hydrate Forming Potential Disinfection By-Product Diethylaminoethyl Diffusion Limited Aggregation Dissolved O anic Carbon Dissolved Organic Matter Direct Observation through the Membrane Technique Diffusive Reflectance Fourier Transform Infrared Spectroscopy Electronic Conductive Carbon Black Electron Dispersive Spectra Ethylene Diamine Tetra Acetic Acid Fulvic Acid... 

Corwen [58] used this method for the analysis of ketones and aldehydes in seawater. Halocarbons were similarly separated from environmental samples by Kaiser and Oliver [59]. There have been many other applications of the technique [60-69]. The major advantage of the headspace method is simplicity in handling the materials. At most, only one chemical, the salt used in the salting-out procedure, needs to be added and in most cases the headspace gas can be injected directly into a gas chromatograph or carbon analyser. On the other hand the concentration of organic materials present is limited by the volume of seawater in the sample bottle. This is very much a batch process. 

Cropek and Kemme (1997/1998) studied the destruction of nitrobenzene (NB) and dinitrobenzene (DNB). Aqueous solutions of these two species were sonolytically treated under two different frequencies. Instrumentation for monitoring the progress of degradation included one or more of the following a total organic carbon instrument, a liquid chromatograph with a UV/visible absorbance detector, and a gas chromatograph/mass spectrometer (GC/MS). 

Vogl, J. and Heumann, K.G. (1998) Development of an ICP-IDMS method for dissolved organic carbon determinations and its application to chromatographic fractions of heavy metal complexes with humic substances. Anal. Chem., 70, 2038-2043. 

Fung et al. [15] have discussed a thermal combustion-ion chromatographic method for the determination of total organic carbon in industrial and potable waters. This method utilises a tube furnace and readily... 

Abbreviations C = C, percentage of unsaturated carbon (largely aromatic) LOPs, lignin oxidation products %BOC, percentage of total dissolved organic carbon that occurs in chromatographically measurable biochemicals. 

A dynamic headspace gas-partitioning method has been used to assess the effect of dissolved organic carbon on the value of H for mirex (Yin and Hassett 1986), and with a gas chromatographic detection system for analysis, this is applicable to native water samples containing mirex. 

Solvent extraction combined with chromatographic techniques generally is used to study organic compounds associated with the atmospheric aerosol. Combustion to C02 is additionally used to determine total organic carbon in the samples. This includes elemental carbon present as soot. Due to the limited efficiency of solvent extraction and because many compounds show-... 

In some instances the method for carbon determination has to be modified, e.g., the determination of trace amounts of what is referred to as dissolved organic carbon in water after inorganic carbon has been removed. This type of carbon determination involves wet oxidation activated by silver ions in a solution of potassium persulphate in sulphuric acid. The oxidation of organic compounds gives carbon dioxide, which is adsorbed by molecular sieves. The molecular sieves are then heated in a flow of helium to desorb the carbon dioxide, the amount of which is measured by a TCD. The lowest concentration of organic carbon that can be measured in water is 0.2—2ppm [55]. The application of chromatographic elemental analysis to the determination of the total carbon content in water has been described [56]. 

The measurement of total organic carbon (TOC) is the best means of assessing the organic content of a water sample [20]. Organic carbon is oxidized to carbon dioxide (CO,) by heat and oxygen, ultraviolet irradiation, chemical oxidants, or by various combinations of these. The CO, may be measured directly by a non-dispersive infrared analyser or it may be reduced to methane and measured by a flame ionization detector in a gas chromatograph or in a TOC analyser thus equipped. The CO2 may also be titrated chemically. 

In heterogeneous photocatalysis experiments, especially in reactions dealing with water detoxification and gaseous pollutant removal, the disappearance of target chemicals, the degree of mineralization of total organic carbon (TOC), and the reaction intermediates can be detected by spectroscopic optical methods (UV-vis and IR), TOC measurements, and chromatographic analysis. 

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). 

The most commonly used mobile phase for SFC is CO2. It is an excellent solvent for many organic molecules, and it is transparent in the UV range. It is odorless, nontoxic, readily available, and inexpensive when compared with other chromatographic solvents. Carbon dioxide s critical temperature of 31°C and its pressure of 72.9 bar at the critical point permits a wide selection of temperatures and pressures without exceeding the operating limits of modem chromatographic equipment. Other substances that have served as mobile phases for SFC include ethane, pentane, dichlorodifluoromethane, diethyl ether, and tetrahydrofuran. 

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