Total organic carbon measurement

Unattended operation possible, loop-sampler option autosampler printer, option inorganic, carbon, purgeable carbon, total carbon and total organic carbon measurements possible... 

This is a fully automated system capable of determining between lpg L 1 and 300pg L 1 total organic carbon. It is equipped with a 36-place autosampler, microprocessor and printer. Total organic carbon measurements down to 40pg L 1 have been achieved at a coefficient of variation of 16.3%. 

COMPARATIVE DIGESTION EFFICIENCIES (% SAMPLE DECOMPOSITION) AS DETERMINED BY RESIDUAL TOC-TOTAL ORGANIC CARBON MEASUREMENTS... 

The concentrations of reactive organic carbon for the model were 20% of the total organic carbon measured in the cores. This percentage was... 

Fig. 2. Carbon isotopic values (with error bars) of individual Precambrian microfossils from single stratigraphic horizons of three geologic units measured by ion microprobe mass spectrometry compared with those of the carbonate and total organic carbon measured in bulk samples of the same geologic units. Values plotted for carbonate and total organic carbon are from Strauss and Moore (1992) for microfossils from the Bitter Springs and Gunflint Formations, from House et al (2000) and those for microfossils from the Dresser Formation, from Ueno et al. (2001).

G. Visco, F. Bellanti, L. Campanella, T. Mazzella, and V. Nobili. Optimization of a photochemical sensor for total organic carbon measurement. Ann. Chim., 95(3—4) 185-198, 2005. 

One important measurement made by geochemists is the Total Organic Carbon (TOC) measurement. The results are expressed as a weight percentage. When the TOC is less than 0.5 percent, the rock is considered unlikely to have enough kerogen to produce oil or gas. 

NOTE The decomposition of DEHA should not be considered too seriously because it is very low initially. At 1,500psig, DEHA breakdown only amounts to 3%, as measured by the total organic carbon (TOC) content. Compare this to HQ, which breaks down to the extent of 43% at the same pressure. 

The third, and largely unexpected, case appeared as a problem in the analysis of petroleum hydrocarbons in seawater [24]. In this case, petroleum hydrocarbons, picked up presumably in the surface layers or surface film, were carried down by the sampling bottles and were measured as par t of the pollutant load of the deeper waters. While the possibility of absorption and subsequent release is obviously most acute with hydrophobic compounds and plastic samplers, it does raise a question as to whether any form of sampler which is open on its passage through the water column can be used for the collection of surface-active materials. The effects of such transfer of material maybe unimportant in the analysis of total organic carbon, but could be a major factor in the analysis of single compounds or classes of compounds. 

MacKinnon MD (1977) The analysis of the total organic carbon in seawater a. Development of methods for the quantification of TOC b. Measurement and examination of the volatile fraction of the TOC. PhD Dissertation. Dalhousie University... 

Of the methods in common use, the two wet oxidation methods offer the best possibilities for further development. The photo-oxidation method in particular is well suited to automatic analysis. In the version of the total organic carbon method published by Collins and Williams [30] the effluent from the quartz photolysis coil could as easily be diverted to the nitrate analysis unit if inorganic nitrogen were also measured, organic nitrogen could become a routine automatic method. 

Because they are so intimately related, for the purposes of this discussion, the categories of total and dissolved organic carbon are combined in this section. Also it is doubtful in any case that anyone ever measures a true total organic carbon in seawater. The total organic carbon should include... 

A dry combustion-direct injection apparatus was applied to water samples by Van Hall et al. [51 ]. The carbon dioxide was measured with a non-dispersive infrared gas analyser. Later developments included a total carbon analyser [97], a diffusion unit for the elimination of carbonates [98], and finally a dual tube which measured total carbon by combustion through one pathway and carbonate carbon through another. Total organic carbon was then calculated as the difference between the two measurements [99]. 

As for all of the fractions of organic material in seawater, the volatile organic carbon fraction is defined by the method by which it is collected. In one of the earliest estimates, Skopintsev [93] defined the volatile fraction as the difference between total organic carbon values, as measured by evaporation and dry combustion, when the evaporations were carried out at room temperature and at 60 °C. Thus Skopintsev s volatile fraction consists of those compounds that are volatile from acidified solution taken to dryness at 60 °C but not at 20 °C. This fraction was found to be between 10 and 15% of the total organic carbon. He also noted a 15% difference in measured organic carbon with his dry combustion method when samples were dried at different temperatures and concluded that this difference was due to the loss of volatiles. 

In further work to that discussed above, MacKinnon [183] has discussed in detail a method for the measurement of the volatile fraction of total organic carbon in seawater. 

Ratio of microbial biomass to total organic carbon Calculation from individual measures Indicates enrichment of microbial biomass relative to total organic carbon determined in nonstandard laboratory with specialized equipment Rice et al. (1996)... 

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