Reliability carbon determinations

X-Ray Diffraction Data. The QI components found in the products of hydrocarbon pyrolysis are generally brittle, infusible solids. Because of this appearance the QI are usually classified under the general heading of coke. However, to more clearly define the nature of the QI produced in this work, x-ray diffraction patterns were obtained. The crystallite parameters for a graphitic matrix, as defined in Table II, were calculated for the QI and are compared in Table II with the same parameters determined for a sample of /3-resins and for a sample of coke obtained from a test carbon anode. The x-ray diffraction pattern for the sample of /3-resins was not well defined, so the value of Lc could not be determined reliably. The values of the other /3-resin parameters are... 

A factor militating against the use of other adsorptives for pore size determination at the present time is the lack of reliable r-curves. The number of published isotherms of vapours such as benzene, carbon tetrachloride or the lower alkanes, or even such simple inorganic substances as carbon dioxide, on a reasonable number of well-defined non-porous adsorbents, is very small. 

The instrumental analyzer procedure, EPA Method 3A, is commonly used for the determination of oxygen and carbon dioxide concentrations in emissions from stationary sources. An integrated continuous gas sample is extracted from the test location and a portion of the sample is conveyed to one or more instrumental analyzers for determination of O9 and CO9 gas concentrations (see Fig. 25-30). The sample gas is conditioned prior to introduction to the gas analyzer by removing particulate matter and moisture. Sampling is conducted at a constant rate for the entire test run. Performance specifications and test procedures are provided in the method to ensure reliable data. 

Danckwerts et al. (D6, R4, R5) recently used the absorption of COz in carbonate-bicarbonate buffer solutions containing arsenate as a catalyst in the study of absorption in packed column. The C02 undergoes a pseudo first-order reaction and the reaction rate constant is well defined. Consequently this reaction could prove to be a useful method for determining mass-transfer rates and evaluating the reliability of analytical approaches proposed for the prediction of mass transfer with simultaneous chemical reaction in gas-liquid dispersions. 

In the million year range, however, there is clearer evidence for isotopic alteration which also apparently increases with age. Unfortunately, at present there are few reliable browser and grazer data beyond the Late Pleistocene, i.e., in the Middle Pleistocene, which would allow determination of the periods during which bone apatite and enamel begin to deviate. The indications are that the timing should be different. Material from the site of Florisbad falls within the late Middle Pleistocene ( 125-200 Ka), but at present carbon isotope data are only available for three species of uncertain and/or opportunistic diets (Brink and Lee-Thorp 1992), so that extent or direction of isotopic alteration is impossible to separate from dietary vagaries. 

In the analysis of complex PAH mixtures obtained from environmental samples, reversed-phase LC-FL typically provides reliable results for only 8-12 major PAHs (Wise et al. 1993a). To increase the number of PAHs determined by LC-FL, a multidimensional LC procedure is used to isolate and enrich specific isomeric PAHs that could not be measured easily in the total PAH fraction because of interferences, low concentrations, and/or low fluorescence sensitivity or selectivity. This multi-dimensional procedure, which has been described previously (Wise et al. 1977 May and Wise 1984 Wise et al. 1993a, 1993b), consists of a normal-phase LC separation of the PAHs based on the number of aromatic carbon atoms in the PAH, thereby providing fractions containing only isomeric PAHs and their alkyl-substituted isomers. These isomeric fractions are then analyzed by reversed-phase LC-FL to separate and quantify the various isomers. 

Clinical chemistry, particularly the determination of the biologically relevant electrolytes in physiological fluids, remains the key area of ISEs application [15], as billions of routine measurements with ISEs are performed each year all over the world [16], The concentration ranges for the most important physiological ions detectable in blood fluids with polymeric ISEs are shown in Table 4.1. Sensors for pH and for ionized calcium, potassium and sodium are approved by the International Federation of Clinical Chemistry (IFCC) and implemented into commercially available clinical analyzers [17], Moreover, magnesium, lithium, and chloride ions are also widely detected by corresponding ISEs in blood liquids, urine, hemodialysis solutions, and elsewhere. Sensors for the determination of physiologically relevant polyions (heparin and protamine), dissolved carbon dioxide, phosphates, and other blood analytes, intensively studied over the years, are on their way to replace less reliable and/or awkward analytical procedures for blood analysis (see below). 

Low-temperature ultraviolet-promoted chemical oxidation has provided more reliable and precise data in the determination of low pg/1 levels of total organic carbon [56,78]. 

The conditions for reliable cyclic voltametry determination of trace Sn concentrations in sea water were investigated. All organotin compounds should be converted to Sn(II) by UV-photolysis adsorption on mercury drop in the presence of 40 pM of tropolone (1) cyclic voltametry stripping shows two cathodic peaks, corresponding to the two-step process Sn(IV) — Sn(II) -> Sn(0)29. A complex of Sn ions with catechol can be accumulated in a glassy carbon mercury film electrode, followed by stripping voltametry measurement in the cathodic direction, at pH 4.2-4.7. Interference occurs when Cu, Cd and Cr are present LOD 0.5 pg/L for 300 s accumulation30. 

The improved methods introduced in the years 1940 to 1945 created new possibilities in this field. The Van Slyke method for quantitative determination of amino acids, based on the measurement of the volume of carbon dioxide evolved in the course of the reaction between amino acids and ninhydrin (V2), was much more reliable than the older methods. At the same time the microbiological methods designed for amino acid determinations (D3, S6) made possible the detection of very small concentrations of these compounds. The application of these... 

Happer157 determined 13C substituent chemical shifts for meta- and para-substituted styrenes in seven different solvents. Data for the side-chain carbons, and in the meta series for the ring carbon para to the substituent, were analyzed as a basis for assessing solvent effects on 07, cr, ar (BA) and cr. The 07 values for NO2 varied from 0.60 in DMSO to 0.71 in CDCI3 in EtOH the value was 0.64. The [Pg.505]

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