Determination of Organic Sulfur Compounds in Extractants

The service conditions in these applications can be characterised into two sets. The first is typified by tubing, hosing and belting where a large contact area of rubber is used but which makes only transient contact with a large volume of food or drink. The second type is typified by can sealants where only a small surface area is exposed to the food or drink but for a prolonged period. 

Sidwell of Rapra Technology [4] carried out a study of the types of organosulfur compounds present in a range of rubber materials and other elastomers and the effect of ageing of various sanitisers and cleaning agents on the migration of these compounds from rubbers in contact with food. 

Sidwell [4] used combined gas chromatography - mass spectrometry and, in some cases, high-performance liquid chromatography (HPLC) to obtain data. 

Elastomers examined included NR, nitrile rubber, ethylene-propylene dimer and a vinylidene fluoride - hexafluoropropylene copolymer. Examination of migrating species was carried out by methods discussed in the EC Framework Directive 89/109/ EC (see Chapter 16). Distilled water and diethyl ether extractants were included in this study. 

Migrant 1st 24 hour extraction 2nd 24 hour extraction 3rd 24 hour extraction after 

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Various other workers have reported on the determination of volatile organic compounds in soils [186,187] and landfill soils [188]. Soil fumigants such as methyl bromide have also been determined by this technique [189]. Trifluoroacetic acid is a breakdown product of hydrofluorocarbons and hydrochlorofluorocarbon refrigerant products in the atmosphere and, as such, due to the known toxicity of trifluoroacetic acid, it is important to be able to determine it in the atmosphere, water and in soil from an environmental point of view [190]. In this method the trifluoroacetic acid is extracted from the soil sample by sulfuric acid and methanol, which is then followed by the derivatisation of it to the methyl ester. The highly volatile methyl ester is then analysed with a recovery of 87% using headspace gas chromatography. Levels of trifluoroacetic acid in soil down to 0.2 ng/g can be determined by the procedure. 

The comparison of a number of dialytic extracts with the parent coals is given in Table 1L These results indicate that the elemental composition of the dialytic extract closely mirrors that of the organic fraction of the coal. Similar conclusions were reached when coal liquids were separated via the dialytic method. The conclusion that dialysis does not concentrate any particular compound type deserves further investigation, since obtaining a representative sample is crucial to the utility of the method. In Table H, it is particularly interesting to note that in each case the "organic sulfur 1 from the classical coal analysis is almost identical to the sulfur content directly determined on the dialytic extract. 

Sulfur Mustard stability in nonpolar solvents has been determined by GC and GC-MS methods. The situation is more complex for Lewisite because GC methods generally involve derivatization with thiols, and are also complicated by the fact that Lewisite and its hydrolysis products give the same compound after derivatization. The solution to this problem can be found by measuring Lewisite without derivatization. In a study reported by Down in 2005 [63], toluene was selected as the extraction solvent because Lewisite slowly decomposed in other organic solvents, such as acetone and hexane. Thermal oligomerization in the injection port was prevented by on-column injection and a deactivated guard column was used to prevent the well-known problems of memory effects and column deterioration that occur with Lewisite. The extracts were analysed by GC-AED and GC-MS with both electron and chemical ionization [63]. More GC-MS techniques will be described in Chapter 4 with respect to the numerous degradation products of Sulfur Mustard. 

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