Determination of Halogens

Chlorine and bromine may be titrated by indirect iodometry due to their standard potential values  

The reactions are achieved in the presence of an excess of potassium iodide. The iodine released is titrated with thiosulfate. It is interesting to notice that chlorine and bromine cannot be directly titrated by thiosulfate, as might be, a priori, predicted from the sole standard potential values. In these conditions, thiosulfate is transformed partly into tetrathionate and into sulfate. The two reactions are of different stoichiometries (see the beginning of the chapter). 

The oxidization of iodide ions with bromine is of great interest in practice for the analysis of organic substances. Some organic structures may indeed fix bromine atoms after reacting with bromine added in excess. The excess is determined by indirect iodometry. 

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Le Bel GL, Williams DT. 1986. Determination of halogenated contaminants in human adipose tissue. 

Tubes for sealed tube reactions, such as the Carius determination of halogens and sulphur, can be made from Pyrex, Monax or soda glass. The mechanical strength of the glasses is about the same, but a soda Carius tube is much more likely to crack as a result of thermal strain than a Pyrex or Monax one. The Carius tubes are usually made from tubing of approximately 20-25 mm diameter and 3 mm wall thickness—Pyrex extra heavy tubing of external diameter 22 mm has a wall thickness of 2-5-4 mm and can be used up to 600°C. 

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]. 

Gron [23] has reviewed methods for the determination of halogenated organic compounds (adsorbable, volatile and extractable), with particular reference to their applicability to wastewaters and marine samples (marine sediments and marine organisms). Typical analytical results for marine... 

For the determination of halogen in liquids weigh the substance in the manner described for C and H determination and introduce the weighing tube into the combustion tube in such a way that the former rests about 8-10 cm. beyond the front end of the long wire gauze roll. For liquids which burn with very great difficulty substitute ammonium nitrate for the potassium chlorate. 

The determination of sulphur by the Carius method is carried out in the same way as is the determination of halogen, but, in place of the silver nitrate, anhydrous barium chloride is here used. 

Seal, heat, and open the tube as described for the determination of halogen. 

The determination of sulphur in the tube with bead packing is carried out in a manner analogous to that employed in the argento-metric determination of halogen (see p. 73). 

For the determination of methoxyl weigh out in the manner described for determination of halogen 20-30 mg. of substance, using a small weighing tube. Transfer the substance to the reaction flask (K) and add a few small crystals of phenol and 0-5 c.c. of acetic anhydride (or glacial acetic acid) in order to dissolve the substance. Then add about 0-2 g. of dry red phosphorus. 

Analysis of the Benzyl Chloride.—The quantitative determination of halogen in substances containing halogen in aliphatic combination is not carried out in a sealed tube by the Carius method (cf. p. 69), but by hydrolysis with standard alcoholic potassium hydroxide solution. Since this method is very often used, a check on the purity of the present preparation may be combined with practice in this method of analysis. 

Determination of halogenated 2-aminobenzophenones (64a-c), which are metabolites of psychotropic drugs, was performed by HPLC with amperometric detection (GCE vs Ag/AgCl) LOQ 750 ng of metabolite/L of biological fluid (urine or serum), with recovery better than 97%183. 

Sithole BB, Williams DT, Lastoria C, et al. 1986. Determination of halogenated phenols in raw and potable water by selected ion gas chromatography-mass spectrometry. J Assoc Off Anal Chem 69 466-473. 

Matthew, B.M. Anastasio, C. (2000) Determination of halogenated mono-alcohols and diols in water by gas chromatography with electron-capture detection. J. Chromatogr., 866, 65-77... 

The lower the peak potential for oxidation of a compound, the more specifically it can be determined (since a lower detector voltage can be used). Therefore compounds such as MMPDA, MDA, DCB, MBOCA, and benzidine (i.e. aromatic diamines) can be more readily determined by HPLC/EC than are the aniline derivatives. This does not imply that HPLC/EC is not useful for the determination of anilines. In fact, a recent paper illustrates the usefulness of HPLC/EC for the determination of halogenated anilines in urine. 

The Determination of Halogenated Chemical Indicators of Industrial Contamination in Water by the Purge and Trap Method Environmental Monitoring and Support Laboratory. U.S. Environmental Protection Agency Cincinnati, OH, 1979 Method 502. 

M. L. Ware, M. D. Argentine, and G. W. Rice, Potentiometric Determination of Halogen Content in Organic Compounds Using Dispersed Sodium Reduction, Anal. Chem. 1988,60, 383. 

Johansson C, Pavasars I, Boren H, Grimvall A, Dahlman O, Morck R, Reimann A (1994) A Degradation Procedure for Determination of Halogenated Structural Elements in Organic Matter from Marine Sediments. Environ Int 20 103... 

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

The application of the displacement of halogen by nickel-aluminum alloy in aqueous alkali to the quantitative determination of halogens in organic compounds (115) is of considerable interest. Many of the above methods, when adapted for analysis, require the use of hydrogen gas, a prepared catalyst, and a hydrogenation apparatus of the conventional type. These requirements are obviated by the use of nickel-aluminum alloy in aqueous alkali, and the method is advantageously used for the quantitative determination of halogen in many aliphatic, aromatic, alicyclic, and heterocyclic compounds. 

Quantitative Determination of Halogen by Means of Nickel-Aluminum Alloy in... 

The isotope dilution technique in LA-ICP-MS has been applied for the direct analysis of sulfur species in gas oil, diesel or heating fuel as described by Boulyga et al. In addition, these authors have developed an analytical method for the direct determination of halogens (Cl, Br and I) in powdered geological and environmental samples using isotope dilution laser ablation ICP-MS. The detection limits of LA-ICP-IDMS are in the low and sub-p,gg range for halogens. ... 

Hoerner G, Kuehn W, Leonhardt D. 1982. [Continuous monitoring of water using process chromatography - determination of halogenated hydrocarbons]. Vom Wasser 59 115-128. (German). 

Pfannhauser W, Thaller A. 1985. [Determination of halogenated solvent residues in water, wastewater, feeds, and food]. Fresenius Z Anal Chem 322 220-222. (German). 

Johansson C., Pavasars I., Boren H., and Grimvall A. (1994) A degradation procedure for determination of halogenated structural elements in organic matter from marine sediments. 

Petrovic et al. [41] reported the determination of halogenated APEO and their degradation products formed during chlorine disinfection in the presence of bromide. These compounds were analysed in sludge, river sediments, surface,... 

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