Carbon measurement methods

Fuel economy is measured usiag a carbon balance method calculation. The carbon content of the exhaust is calculated by adding up the carbon monoxide (qv), carbon dioxide (qv), and unbumed hydrocarbons (qv) concentrations. Then usiag the percent carbon ia the fuel, a volumetric fuel economy is calculated. If the heating value of the fuel is known, an energy specific fuel economy ia units such as km/MJ can be calculated as well. 

Ash and Inorganic Constituents. Ash may be measured gravimetdcaHy by incineration in the presence of sulfudc acid or, more conveniendy, by conductivity measurement. The gravimetric result is called the sulfated ash. The older carbonate ash method is no longer in use. Ash content of sugar and sugar products is approximated by solution conductivity measurements using standardized procedures and conversion factors. 

Ogura and Hanya [62-65] investigated the components of the ultraviolet absorption in an attempt to devise a useful method for oceanic dissolved organic carbon measurements. They concluded that while the method might have limited application in coastal waters, most of the absorption in oceanic waters was due to the inorganic components, principally nitrate and bromide ions. 

The electrochemical behaviour of trace concentrations of triphenylstannyl acetate, using a mercury film-glassy carbon electrode, was investigated by various measuring methods cyclic voltametry, differential pulse voltametry and controlled-potential electrolysis. Determination by DPASV (differential pulse ASV) of water and fish samples has LOD 2.5 nM98. 

Venkataraman, C., J. M. Lyons, and S. K. Friedlander, Size Distributions of Polycyclic Aromatic Hydrocarbons and Elemental Carbon. 1. Sampling, Measurement Methods, and Source Characterization, Environ. Sci. Technol, 28, 555-562 (1994a). 

While the carbon arc method yields products in amounts that are easily characterized, there is a number of caveats of which one must be aware. Since the carbon arc operates at extremely high temperatures (>2000 °C) and emits copious amounts of light, there is the very real possibility of pyrolysis and/or photolysis of both substrate and products. These problems may be minimized by carrying out control experiments in which pyrolysis and photolysis products are identified and excluded. Maximum yields in carbon arc reactions are obtained when carbon and substrate are cocondensed. However, this technique can result in pyrolysis of substrate, which can be avoided by alternately depositing substrate and carbon on the cold reactor walls. Often both methods are employed in order to identify pyrolysis products. Since the carbon arc results in removal of macroscopic pieces of graphite from the rods, it is impossible to measure product yields based on actual carbon evaporated. 

Carbon Monoxide. Methods for determining carbon monoxide include detection by conversion to mercury vapor, gas filter correlation spectrometry, TDLAS, and grab sampling followed by gas chromatograph (GC) analysis. The quantitative liberation of mercury vapor from mercury oxide by CO has been used to measure CO (73). The mercury vapor concentration is then measured by flameless atomic absorption spectrometry. A detection limit of 0.1 ppbv was reported for a 30-s response time. Accuracy was reported to be 3% at tropospheric mixing ratios. A commercial instrument providing similar performance is available. 

Figure 9.6 compares the weight percentages of carbon estimated by the TEOM and TPO-IR on the samples after reaction at CH4 C02 C0 H2 molar ratios of 1 1 0 0, 0.75 0.75 0.5 0.5, and 0.5 0.5 1 1. The good linear correlation between the weight of carbon measured by both methods confirmed that these results were consistent. Based on this comparison, it was concluded that the TEOM was effective for studying the dynamic process of carbon formation on catalysts. 

The method of determining heats of combustion has been described above, for carbon. This method, with use of a bomb calorimeter, is the customary basis for determining the value of a fuel, such as coal or oil. A weighed sample of the fuel is placed in the bomb calorimeter, the bomb is filled with oxygen, and the fuel is burned. The fuel value or calorific value of the fuel is considered to be measured by its heat of combustion, and when large amounts of fuel are purchased the price may be determined by the result of tests in a bomb calorimeter. 

The use of Cd/Ca measurements in the tests of benthic foraminifera for deep-water nutrient reconstructions was developed in parallel with the carbon isotope method. Cadmium concentrations in seawater follow a nutrient-like distribution, while calcium concentrations simply reflect variations in salinity. The benthic foraminifera incorporate the cadmium and calcium into their shells in proportion to their presence in seawater, which allows for the reconstruction of deep-water cadmium (and thus macronutrient) distributions. 

Since the radioactive sample material from most methods of sample preparation is in intimate contact or in actual solution with the phosphor, the detection of emitted particles or radiation is highly efficient and may even approach 100%. Problems of self-absorption of the emissions are thus absent, or considerably smaller than those associated with planchette counting of solid samples. This is of particular importance for the measurement of low energy beta emitters such as tritium and carbon-14. On the other hand, the measurement method has intrinsic drawbacks such as quenching and chemiluminescence. 

The reference principle for on-line methods has to be different as compared to classic dual-inlet isotope ratio analysis, as it is not possible to introduce sample and reference gas in exactly the same maimer into the mass spectrometer. Reference gas pulses have to be set at different points during one mn, but also laboratory standards with knovm 8-values have to be analysed periodically and exactly in the same manner and under the same conditions as the samples under investigation (identical treatment principle ]13]). A general problem of on-line HPLC and GC methods in isotope ratio analysis is the lack of international reference materials suitable to fulfil the above mentioned requirements. This implies the necessity to establish suitable laboratory standards by EA (elemental analysis) or classic measurements. Meanwhile, also efforts in supplying suitable international organic standards have been overtaken by the IAEA (e.g. caffeine, glutamic acid ]176, 177]). This programme (benzoic acid reference materials with different 8 0-values) will also support the on-line EA and GC 8 0-meas-urement by reductive pyrolysis (carbon reduction) methods (standardisation problems are compiled in ]178]). 

Method. Add known and similar weights of cyanoacrylate sample to four grade B plastic volumetric flasks followed by increasing concentrations of the analyte Nb (0.0, 0.5, 1.0 and 2.0 ppm) and dilute to volume with 50 50 acetic acid and propylene carbonate. Measure the intensity of each concentration and plot against the analyte concentration. The straight line is extrapolated to the negative concentration axis and the point where the calibration line cuts the concentration line is the concentration of analyte in the sample. Similarly, prepare the same concentration of standards without the sample and measure intensity for each concentration. Plot a calibration curve of intensity versus concentration and if this line is parallel to the sample curve then the standard addition method can be used to quantify the level of metal present. The control standard is also prepared in the same manner as for the sample. 

This group is mainly formed by silica or carbon membranes. For silica in the small pore and intermediate pore region very good combinations of selectivity and fluxes are reported. The porosity of the membrane seems to be too low however (note good measurement methods for supported microporous membranes do not exist). Porosities of at least 20% of theoretical density should give considerable improvement in the permeance. A strategy to overcome this is. 

---