Measurement methods carbon monoxide

Reference methods for criteria (19) and hazardous (20) poUutants estabHshed by the US EPA include sulfur dioxide [7446-09-5] by the West-Gaeke method carbon monoxide [630-08-0] by nondispersive infrared analysis ozone [10028-15-6] and nitrogen dioxide [10102-44-0] by chemiluminescence (qv) and hydrocarbons by gas chromatography coupled with flame-ionization detection. Gas chromatography coupled with a suitable detector can also be used to measure ambient concentrations of vinyl chloride monomer [75-01-4], halogenated hydrocarbons and aromatics, and polyacrylonitrile [25014-41-9] (21-22) (see Chromatography Trace and residue analysis). 

The increased throughput capahihty of the AutoAnalyzer and electronic balance, coupled with the reduction in staff time, substantially increased productivity. Further benefits accrued because implementation of the automatic techniques also coincided with a need for the LGC to measure the carbon monoxide yields of cigarettes because of the interest in the carbon monoxide dehveries of cigarettes hy epidemiologists working in the field of cardiovascular diseases. A development programme was initiated to find a method... 

Gas chromatographic methods measure the carbon monoxide content of blood. Y/hen blood is treated with potassium ferricyanide, carboxyhemoglobin is converted to methemoglobin, and the carbon monoxide is released into the gas phase. Measurement of the released carbon monoxide may be performed by GC using a molecular sieve column and a thermal conductivity detector. A lower detection limit is achieved by incorporating a reducing catalyst (e.g., nickel) between the GC column and the detector to convert... 

The spectrophotometric methods generally compare favorably with gas chromatographic procedures at carboxy-hemoglobm concentrations greater than 2% to 3%, but their precision is poor below these levels. Therefore, they are sufficiently accurate and precise for measurement of carbon monoxide after exogenous exposure but are too insensitive to detect the increased endogenous production of carbon monoxide that occurs in hemolytic anemias. 

Accuracy of the diaphragm gas meter is verified against either a wet test meter or a Sierra instruments 616 E-36 hot wire aneomemeter. On a yearly basis, a third party laboratory verifies chamber operation and air exchange rate measurements. The carbon monoxide decay is the method used to verify air exchange rate measurements(13). However, other researchers have reported using formaldehyde, propane, sulfur hexafluoride, and carbon dioxide as... 

As with any analytical method, the success of the bioassay is highly dependent on how the samples are collected and prepared. Care must be taken during all of the steps of the analysis to ensure that oxygen is not allowed to bind with myoglobin and that all measurements are carried out very carefully. Furthermore, attention to sample acquisition must be taken to ensure that small gas bubbles are not entrained in the samples when they are collected as this leads to errors (Kapic, 2005). Although difficult to use, the bioassay technique, once mastered, may be successfully used to accurately measure dissolved carbon monoxide concentrations. 

The saturation coverage during chemisorption on a clean transition-metal surface is controlled by the fonnation of a chemical bond at a specific site [5] and not necessarily by the area of the molecule. In addition, in this case, the heat of chemisorption of the first monolayer is substantially higher than for the second and subsequent layers where adsorption is via weaker van der Waals interactions. Chemisorption is often usefLil for measuring the area of a specific component of a multi-component surface, for example, the area of small metal particles adsorbed onto a high-surface-area support [6], but not for measuring the total area of the sample. Surface areas measured using this method are specific to the molecule that chemisorbs on the surface. Carbon monoxide titration is therefore often used to define the number of sites available on a supported metal catalyst. In order to measure the total surface area, adsorbates must be selected that interact relatively weakly with the substrate so that the area occupied by each adsorbent is dominated by intennolecular interactions and the area occupied by each molecule is approximately defined by van der Waals radii. This... 

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. 

The methods of choice for beryUium oxide in beryUium metal are inert gas fusion and fast neutron activation. In the inert gas fusion technique, the sample is fused with nickel metal in a graphite cmcible under a stream of helium or argon. BeryUium oxide is reduced, and the evolved carbon monoxide is measured by infrared absorption spectrometry. BeryUium nitride decomposes under the same fusion conditions and may be determined by measurement of the evolved nitrogen. Oxygen may also be determined by activation with 14 MeV neutrons (20). The only significant interferents in the neutron activation technique are fluorine and boron, which are seldom encountered in beryUium metal samples. 

A convenient method for assessing the extent of surface oxidation is the measurement of volatile content. This standard method measures the weight loss of the evolved gases on heating up to 950°C in an inert atmosphere. The composition of these gases consists of three principal components hydrogen, carbon monoxide, and carbon dioxide. The volatile content of normal furnace blacks is under 1.5%, and the volatile content of oxidized special grades is 2.0 to 9.5%. 

The primary reference method used for measuring carbon monoxide in the United States is based on nondispersive infrared (NDIR) photometry (1, 2). The principle involved is the preferential absorption of infrared radiation by carbon monoxide. Figure 14-1 is a schematic representation of an NDIR analyzer. The analyzer has a hot filament source of infrared radiation, a chopper, a sample cell, reference cell, and a detector. The reference cell is filled with a non-infrared-absorbing gas, and the sample cell is continuously flushed with ambient air containing an unknown amount of CO. The detector cell is divided into two compartments by a flexible membrane, with each compartment filled with CO. Movement of the membrane causes a change in electrical capacitance in a control circuit whose signal is processed and fed to a recorder. 

Performance Specifications for Automated Analytical Methods for Measuring Carbon Monoxide... 

Carbon monoxide chemisorption was used to estimate the surface area of metallic iron after reduction. The quantity of CO chemisorbed was determined [6J by taking the difference between the volumes adsorbed in two isotherms at 195 K where there had been an intervening evacuation for at least 30 min to remove the physical adsorption. Whilst aware of its arbitrariness, we have followed earlier workers [6,10,11] in assuming a stoichiometry of Fe CO = 2.1 to estimate and compare the surface areas of metallic iron in our catalysts. As a second index for this comparison we used reactive N2O adsorption, N20(g) N2(g) + O(ads), the method widely applied for supported copper [12]. However, in view of the greater reactivity of iron, measurements were made at ambient temperature and p = 20 Torr, using a static system. 

Chemisorption measurements (Quantachrome Instruments, ChemBET 3000) were conducted in order to determine the metal (Co) dispersion. Therefore, the nanomaterial catalysts were reduced under a hydrogen flow (10% H2 in Ar) at 633 K for 3 h. The samples were then flushed with helium for another hour at the same temperature in order to remove the weakly adsorbed hydrogen. Chemisorption was carried out by applying a pulse-titration method with carbon monoxide as adsorbing agent at 77 K. The calculation of the dispersion is based on a molar adsorption stoichiometry of CO to Co of 1. 

Up to now, sensors using this parameter have not been taken into consideration, as they are generally not selective. Water for instance is traceable in air because its velocity of sound is significantly higher. The VOS of carbon dioxide is just around 1/3 the VOS of air. In a mixture of air, water and C02 none of the compounds can be quantified. As the VOS of carbon monoxide is similar to that of air, CO cannot be quantifiedby this method either. Hence, sensors based on acoustic principles cannot be taken into consideration neither for the measurement of single species in a flue gas flow nor for the identification of fuel gases. 

The difficulty in detecting surface hydride formation is that hydrogen is nearly always contained in the bulk structure of the carbons. Hydrogen is not easily determined with sufficient accuracy if only small concentrations are present. Precise analytic methods should be used in the measurement of the hydrogen uptake of carbons that were prepared with rigorous exclusion of hydrogen-containing contaminants. Carbon formed by the disproportionation of carbon monoxide... 

The vertical IPs of CO deserve special attention because carbon monoxide is a reference compound for the application of photoelectron spectroscopy (PES) to the study of adsorption of gases on metallic surfaces. Hence, the IP of free CO is well-known and has been very accurately measured [62]. A number of very efficient theoretical methods specially devoted to the calculation of ionization energies can be found in the literature. Most of these are related to the so-called random phase approximation (RPA) [63]. The most common formulations result in the equation-of-motion coupled-cluster (EOM-CC) equations [59] and the one-particle Green s function equations [64,65] or similar formalisms [65,66]. These are powerful ways of dealing with IP calculations because the ionization energies are directly obtained as roots of the equations, and the repolarization or relaxation of the MOs upon ionization is implicitly taken into account [59]. In the present work we remain close to the Cl procedures so that a separate calculation is required for each state of the cation and of the ground state of the neutral to obtain the IP values. 

Although a number of methods have been proposed for the biological monitoring of occupational methylene chloride exposure, measurement of urinary methylene chloride levels may be the most suitable. The measurement of urinary methylene chloride is nonin-vasive, not influenced by smoking as are COHb or carbon monoxide levels in alveolar air, and may reflect cumulative exposures more accurately "... 

B.E.T. method using nitrogen, since nitrogen is chemisorbed at — 196°C. The hydrogen adsorption at this temperature measures the surface more accurately and is in close agreement with the chemisorption of carbon monoxide at both liquid nitrogen and room temperature and with the van der Waal s adsorption of krypton. 

In vitro. The activity or absolute level of enzymes such as cytochrome P-450 and glucuronosyl transferase can be measured in cells, tissue fractions, or subcellular fractions (e.g., microsomes) and compared with those from control animals. The activity is measured by using a particular substrate for each of the isoforms of the enzyme (e.g., cytochrome P-450 or UDPGT) of interest. The total level of cytochrome P-450 could be determined by spectrophotometry using standard methods (e.g., carbon monoxide binding and difference spectra). Alternatively, the level of protein can be determined by gel electrophoresis and Western blotting, and this would allow the separation of different isoforms. 

The precipitation of mercuric acetylide resulted in alkali consumption so that titrating the excess hydroxide gave a direct measure of the amount of acetylide and hence the concentration of acetylene in the gas mixture. The more usual method, precipitating silver acetylide from ammoniacal silver nitrate, was unsatisfactory in this case since the carbon monoxide in the product gases reduced the silver nitrate to silver. 

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