Halogens, determination Combustion methods

It is seen by examination of Table 1.11(b) that a wide variety of techniques have been employed including spectrophotometry (four determinants), combustion and wet digestion methods and inductively coupled plasma atomic emission spectrometry (three determinants each), atomic absorption spectrometry, potentiometric methods, molecular absorption spectrometry and gas chromatography (two determinants each), and flow-injection analysis and neutron activation analysis (one determinant each). Between them these techniques are capable of determining boron, halogens, total and particulate carbon, nitrogen, phosphorus, sulphur, silicon, selenium, arsenic antimony and bismuth in soils. 

Kirsten, W. J. Hot-Flask Combustion Methods for Decimilligram Determination of Halogen and Other Elements in Organic Compounds. Microchem. J. 7, 34 (1963). 

It will seldom be necessary in this course to resort to methods of ultimate analysis, and it is for this reason that combustion methods for carbon, hydrogen, and nitrogen are omitted from this chapter. This is true also of the Carius determination for halogens and the fusion methods for sulfur, arsenic, and phosphorus. In dealing with compounds of unusual difficulty, the methods of ultimate analysis may have to be employed, but imder such circumstances the student is directed to other som-ces where directions will be found in more detail than would be justifiable here. 

Application of the oxygen-flask combustion method to the determination of fluorine in organic combination has now been made by a number of workers. The fluoride in solution after combustion may be determined by thorium nitrate titration or colorimetrically as the alizarin complexan chelate or with a chloranilate (see Halogen Acids and Salts, p. 302). A method based upon the alizarin complexan chelate is given in Appendix IV. 

Applications Basic methods for the determination of halogens in polymers are fusion with sodium carbonate (followed by determination of the sodium halide), oxygen flask combustion and XRF. Crompton [21] has reported fusion with sodium bicarbonate for the determination of traces of chlorine in PE (down to 5 ppm), fusion with sodium bisulfate for the analysis of titanium, iron and aluminium in low-pressure polyolefins (at 1 ppm level), and fusion with sodium peroxide for the complexometric determination using EDTA of traces of bromine in PS (down to 100ppm). Determination of halogens in plastics by ICP-MS can be achieved using a carbonate fusion procedure, but this will result in poor recoveries for a number of elements [88]. A sodium peroxide fusion-titration procedure is capable of determining total sulfur in polymers in amounts down to 500 ppm with an accuracy of 5% [89]. 

BS 6425-1 Test On Gases Evolved During The Combustion Of Materials From Cables. Method For Determination Of Amount Of Halogen Acid Gas Evolved During Combustion Of Polymeric Materials Taken From Cables, BSI British Standards Institution, London, U.K., 1990. 

EN 50267-2 Common Test Methods For Cables Under Fire Conditions—Test On Gases Evolved During Combustion Of Materials From Cables—Procedures—Determination Of The Amount Of Halogen Acid Gas, Brussels, Belgium, 1999. 

Yur ev et al. 2 prepared deuteriated selenophenes from the respective halogenated compounds by halogen-deuterium replacement. Thus, 2-deuterio-, 2,5-dideuterio-, tetradeuterioselenophene, 3-methyl-, and 5-methyl-2-deuterioselenophene were obtained from the corresponding iodoselenophenes on reduction by zinc in deuteriated acetic acid. 3-Deuterioselenophene was obtained from 3-selenienyl-lithium hydrolyzed with deuteriated acetic acid at — 7 0°C the lithium derivative was obtained from 3-bromoselenophene and ethyllithium, also at — 70°C. The deuterium content was determined by combustion, the water being analyzed by the drop method.43... 

Earlier work of this school was concerned to establish heats of formation of halogen-containing organic compounds by measuring heats of hydrolysis. Heats of hydrolysis of acetyl fluoride, chloride, bromide, and iodide402 of the chloro-substituted acetyl chlorides oi of the benzoyl halides and of chloral and bromal 3 have also been made. Comparison with heats of formation derived from heats of combustion is not normally possible, but there is a large discrepancy between the two methods for benzoyl chloride, where an early combustion measurement is available, in the sense that the determined heat of combustion appears to be about 14 kcal low. 

Other major shale constituents such as C, H, N, and S are determined by thermal decomposition and instrumental detection methods. Oxygen is determined by 14 MeV neutron activation analysis. Parr or Leco BTU bomb combustion and subsequent ion chromatographic determination is used for halogens, sulfate and nitrate. Ion chromatography is also suitable for anionic characterization of shale process waters. Two analytical procedures for oil shales should be used with caution. Kjeldahl nitrogen procedure has been found to give reproducible but considerably low results for certain oil... 

Combustion of the sample in an oxygen combustion flask (Alcino et al., 1965) followed by ion chromatography is an attractive method for the analysis of sulfur in humic substances. Not only does the method require relatively little sample and provide high sensitivity, but it also allows simultaneous determination of halogens. One must be sure that sulfur is not rendered insoluble by ash constituents such as calcium. 

Manahan and Chassaniol (Cosa Instruments and Dionex) describe an oxidative combustion followed by ion chromatographic conductometric method for the determination of a number of nonmetallic elements such as sulfur and halogens in liquid and gaseous hydrocarbons. A standard based on this technique is under development in ASTM for designation as a standard method. 

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