Gas analysers

After adequate analitical prepai ation according to standai d EPA method 608 samples were analysed gas chromatographic on a gas chromatograph 8500 Perkin Elmer, in glass and capilar columns using a capture electron detector and mass spectrometry, temperature program. 

Flame ionisation (FID) Organic compounds n2 The sample it fed lo a Hyair flame. The latter contains relatively few ions but does contain atoms of high kinetic energy. The flame produces large numbers of positive ions and secondary electrons from the trace organic materials in the sample gax. A potential is applied across the detector 100[Pg.524]

Surface area. Measurements of the surface area (BET) were done employing the Micromeritics Instrument Corporation ASAP 2000, The measurements were taken over the pressure range 0.001 to 0.1 MPa and at 21 °C, using nitrogen as an analysing gas. 

The amount of some gases, such as SO2 [73], CO [74], can be automatically continuously measured by polarographic analyzers [75]. Measuring electrodes with a constant surface, e.g. carbon, platinum, gold disks or rods are most often used. Present research is concentrated on the so-called coulometric analyzers [73]. The analysed gas is brought by the shortest route directly to the measuring electrode. The substance to be determined is completely reduced or oxidized electrochemically at a large area electrode. 

As far as separation techniques are concerned, they can be implemented on automatic continuous analysers or robot stations as ancillary modules (dia— lysers, ion exchangers, liquid-liquid extractors). As stated in Chapter 12, chromatographic processes —particularly column (HPLC and GC), but occasionally also planar chromatographic purposes— are commonly the subject of automation. A conventional chromatograph furnished with a system for sequential introduction of samples —which can even be partially treated in a continuous fashion before of after column separation (derivatlration and post-column techniques)— markedly resembles continuous flow analysers. Gas and liquid chromatographs are often used as separative-determinative modules in robot-stalons. 

A large variety of analysers such as ion chromatographs, mass spectrometers, digital titrators, calorimeters, specific ion analysers, gas and liquid chromatographs and octane number analysers are manufactured with built-in microprocessors. 

Prior to spectral recording the sample was treated, according to the following procedure the catalyst was heated progressively to 623 K (2.5 K.min ) under O2 (5 %) in He and maintained for 3 hours in these conditions (calcination). It was then exposed (under flow 25 cmlmiir GHSV = 50000 h ) to different previously analysed gas mixtures. 

The glycerol 1-alkyl ethers, which are especially extensively distributed in nature, may be analysed gas chromatographically as their isopropylidene derivatives [55, 184] (see Table 71, p. 399) or as alkoxyacetaldehydes after fission with sodium metaperiodate [10] (see Table 71, p. 399). Trifluoroacetates (TFA-derivatives) [222] (see also [62]) (see Table 71, p. 399) and, in particular, trimethylsilyl ethers (TMS-derivatives) [222] (see Table 71, p. 399) are also suitable for gas chromatography of the isomeric glycerol 1- and 2-alkyl ethers or of other alkyl ethers which contain at least one free hydroxyl group. 

Much of the preceding advice about analysing gas data can also be applied to vapour data. Vapour data can also play an important role in validating the results of risk assessments that are based on soil and groundwater concentrations of volatile contaminants. 

In some analyses Ga and Fe are separated from other species by extracting the former two from a 6-M HCl solution with ether. The Fe is reduced to Fe e g., by means of Hg, and the Ga is extracted again. 

Deployment of a multi-gas system to analyse gas emissions from the fumaroles of La Fossa crater, Vulcano, Italy, is illustrated in Fig. 15.2a. To make in situ... 

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