Non-dispersive infrared

The catalysts were tested for their CO oxidation activity in an automated microreactor apparatus. The catalysts were tested at space velocities of 7,000 -60,000 hr . A small quantity of catalyst (typically 0.1 - 0.5 g.) was supported on a frit in a quartz microreactor. The composition of the gases to the inlet of the reactor was controlled by mass flow controllers and was CO = 50 ppm, CO2 = 0, or 7,000 ppm, HjO = 40% relative humidity (at 25°C), balance air. These conditions are typical of conditions found in spacecraft cabin atmospheres. The temperature of the catalyst bed was measured with a thermocouple placed half way into the catalyst bed, and controlled using a temperature controller. The inlet and outlet CO/CO2 concentrations were measured by non-dispersive infrared (NDIR) monitors. 

The deprotection of carbobenzyloxy protected phenylalanine was carried out in a low-pressure test unit (V= 200 ml) equipped with a stirrer, hydrogen inlet and gas outlet. The gas outlet was attached to a Non Dispersive InfraRed (NDIR) detector to measure the carbon dioxide. During the reaction the temperature was kept at 25 °C at a constant agitation speed of 2000 rpm. In a typical reaction run, 10 mmol of Cbz protected phenylalanine and 200 mg of 5%Pd/C catalyst were stirred in a mixture of 70 ml ethanol/water (1 1). The Cbz protected phenylalanine is not water-soluble but is quite soluble in alcoholic solvents conversely, the water-soluble deprotected phenylalanine is not very soluble in alcoholic solvents. Thus, the two solvent mixture was used in order to keep the entire reaction in the solution phase. Twenty p.1 of the corresponding modifier was added to the reaction mixture, and hydrogen feed was started. The hydrogen flow into the reactor was kept constant at 500 ml/minute and the progress of the reaction was monitored by the infrared detection of C02 in the off-gas. 

Hannaker and Buchanan [82] differ from Menzel and Vaccaro [46] in that they use Carbosorb or soda asbestos tubes to estimate the carbon dioxide produced, instead of the non-dispersive infrared analyser used by the latter workers. 

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]. 

Van Hall et al. [100] inject a 20 litre sample into a high-temperature furnace at 950 °C containing catalyst to promote oxidation of carbon compounds to carbon dioxide, which is then passed into a non-dispersive infrared analyser. The carbonate interference can be determined by passing an acidified portion of the sample through a low-temperature furnace [101-103]. 

Sharp [48] has described a dry combustion-direct injection system built for oceanographic analyses. This unit used 100 xl samples, injected into a 900 °C oven in an atmosphere of oxygen. The output from a non-dispersive infrared carbon dioxide analyser was linearised and integrated. 

The various combustion methods differ primarily in the method of measuring the carbon dioxide generated from the organic carbon. The first really sensitive carbon dioxide detector and the one still most used is the non-dispersive infrared gas analyser. The detecting element senses the difference in absorption of infrared energy between a standard cell filled with a gas with no absorption in the infrared, and a sample cell. Water vapour is the only serious interference, hence the carbon dioxide must be dried before any measurements are made. 

Carbon analysers using the non-dispersive infrared analysers have been described by Kuck et al. [ 144] and by Ernst [ 145], among others. 

An alternative method for the determination of particulate organic carbon in marine sediments is based on oxidation with potassium persulfate followed by measurement of carbon dioxide by a Carlo Erba non-dispersive infrared analyser [152,153]. This procedure has been applied to estuarine and high-carbonate oceanic sediments, and results compared with those obtained by a high-temperature combustion method. 

In this method volatile organic matter in seawater is concentrated on a Tenax GC solid adsorbent trap and dry-ice trap in series. The trapped organic material is then desorbed and oxidised to carbon dioxide, which is measured with a non-dispersive infrared analyser. A dynamic headspace method was used for the extraction with the assistance of nitrogen purging. Dynamic headspace analysis [184] is an efficient extraction procedure. The efficiency of extraction... 

The unique appearance of an infrared spectrum has resulted in the extensive use of infrared spectrometry to characterize such materials as natural products, polymers, detergents, lubricants, fats and resins. It is of particular value to the petroleum and polymer industries, to drug manufacturers and to producers of organic chemicals. Quantitative applications include the quality control of additives in fuel and lubricant blends and to assess the extent of chemical changes in various products due to ageing and use. Non-dispersive infrared analysers are used to monitor gas streams in industrial processes and atmospheric pollution. The instruments are generally portable and robust, consisting only of a radiation source, reference and sample cells and a detector filled with the gas which is to be monitored. 

If it is required to quantify inorganic carbon the sparged gas may be directed to the non-dispersive infrared analyser for quantification. 

OIC Analytical instruments produce the fully computerized model 700 total organic carbon analyser. This is applicable to soils and sediments. Persulphate oxidation at 90-100°C non-dispersive infrared spectroscopy is... 

With the exception of instrumental dry combustion methods [32], the techniques referred to above for the analysis of organic (and total) carbon in sediments are time consuming (e.g. 2-3h). An instrumental technique described by Van Hall and Stenger [33] makes use of a non-dispersive infrared detector and measures the carbon dioxide resulting from the combustion of the carbonaceous compounds. Total and inorganic carbon can be differentiated by the use of different combustion columns and temperatures. 

A feasible solution for this complex challenge is to implement at least two analytical methods with which the course of the reaction can be followed a fast first method that allows qualitative control of the status of the catalyst performance and a second accurate, and in most cases more time consuming, analysis method that will allow a detailed evaluation of catalyst performance. The two analysis methods can be run on one analytical unit, e.g. a gas chromatograph with two different analysis protocols, or separate analytical units such as a gas chromatograph for accurate performance evaluation in combination with a non-dispersive infrared unit for fast qualitative analysis. 

Abstract In routine chemical measurements traceability can be achieved by using analytical instruments calibrated against primary reference materials. In the present work the calibration of a C02 non-dispersive infrared (NDIR) analyzer with measuring range 0 2000 mol/mol of C02 and a resolution of 5 mol/mol is reported. A procedure with working reference gas mixtures (WRMs) has been adopted, which requires seven calibration points. Primary reference gas mix-... 

Non-dispersive infrared analyzers are usually employed to determine carbon dioxide concentration at atmospheric levels, as they are stable, user friendly, and suited to continuous monitoring. At the Istituto di Metrologia G. Colonnetti (IMGC), as in other metrology laboratories, the determination of the C02 concentration in air is carried out for different purposes in mass, length, and environmental measurements. As NDIR spectroscopy is not a primary method of analytical measurement it does not provide direct traceability to the SI it is hence necessary to refer the obtained results to traceable reference materials, namely PRMs of C02 in N2 at appropriate concentrations. 

Experiments are currently in progress to measure CO and NO concentrations in a flat flame burner by diode laser spectroscopy. Comparative measurements are also being made using microprobe sampling with subsequent analysis by non-dispersive infrared and chemiluminescent techniques. Some preliminary laser absorption results for CO are reported here initial results for NO have been published separately (4). Also reported are initial data for collision halfwidths in combustion gases. 

In the laboratories of BASF (Badische Anilin- and Soda-Fabrik) at Ludwigshafen, the importance of infrared spectroscopy for industrial purposes was realized as early as the 1930 s. The first IR instrument with a modulated beam was built by Lehrer in 1937 and modified to a double beam instrument with optical compensation in 1942. Luft described the first non-dispersive infrared analyzer in 1943. He used the gas to be analyzed as absorber in a photo-acoustic detector cell. Thus, the instrument was sensitive only to this gas. He also provided a survey of early industrial applications of infrared spectroscopy (Luft, 1947). 

According to IPCS (1999), the analyzer system consists of an analyzer as well as sample preconditioning components fitted with a moisture control system such as the Non-Dispersive-Infrared (NDIR) analyzer. The infrared absorption near 4.6 pm, characteristic of CO, is used to measure its concentration. The most sensitive analyzers can detect CO concentrations as low as 0.05 mg/m (0.044 ppm). The NDIR analyzer designed by Luft (1962) is considered appropriate because it is little affected by flow rate, requires no wet chemicals, has a short response time, and is sensitive over wide concentration ranges. 

Samples of the exit gas were withdrawn through 3.2-mm quartz tubing at about 0.8 cm /sec. The gas passed through a condenser, a water trap, a tube containing Drierite, and a vacuum pump and was collected in a Teflon bag for analysis. CO and CO2 were determined by non-dispersive infrared, O2 by paramagnetic analysis, NO, by chemiluminescence, and hydrocarbons by flame ionization. N2 and H2O were calculated from stoichiometry. 

Emissions-measuring instruments used in this program consisted of non-dispersive infrared (NDIR) analyzers for CO, CO2, and NO. A modified flame ionization detector (FID) was used to measure HC. Modifications insured that the instrument would detect the unbumed... 

FIGURE 1.11 Monthly average concentration of carbon dioxide in dry air observed at Mauna Loa Observatory, Hawaii from March 1958 to April 1995. Note The measurements were made with a continuously recording non-dispersive infrared gas analyzer. The smooth curve fit is a fit of the data to a four harmonic annual cycle which increases linearly with time plus a spline fit of the interannual component of the variation. From Whorf (1996). 

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