Halogen-containing substances

Note Chloramines do not require exposure to chlorine gas before application of o-toluidine. A range of halogen-containing substances (e.g. bromazine, hexachloro-cyclohexane isomers) can be detected with o-toluidine (1 % in ethanol) after subsequent irradiation with UV light (k = 254 or 366 nm 10-15 min) [1, 8]. 

Halogen-containing substances e. g. chlorine-containing insecticides [1, 7] such as aldrin, dieldrin, DDT, perthane,... 

Peroxides oxidize N,N-DPDD to Wurster s red, a semiquinone diimine derivative [4]. Similarly Wurster s red is also produced from N,N-DPDD by reaction with halogen-containing substances in the presence of sodium ethylate and UV light and by reaction with the chlorinated triazines produced by reaction with chlorine [7]. 

In the case of halogen-containing substances (e. g. insecticides) the chromatograms are moistened by spraying with water after treatment with the reagent and then exposed to unfiltered UV light for ca. 1 min [1, 7] or to sunlight for 30 min [8]. 

Peroxides oxidize TPDD to Wurster s blue, a product with a semiquinone diimine structure [1]. Similarly Wurster s blue is also produced from TPDD by reaction with halogen-containing substances produced by the reaction of aromatic amines and triazines with chlorine gas. 

Electron capture All substances that have affinity to capture electrons no resonse for aliphatic and naphthenic hydrocarbons Excellent for halogen-containing substancs, 0.05-1 pg, 50 ppt-1 ppm Poor Very sensitive to impurities and temperature changes quantitative analysis complicated concentration sensitive... 

The ionization of compounds containing nitrogen and phosphorus, in particular, is made easier in the presence of alkali atoms in the ionization zone close to the surface of the bead. According to recent theory, the alkali atoms serve as electron carriers from the heated salt beads to the compounds. Larger quantities of halogen-containing substances... 

Halogen-containing substances are usually electrolytically reduced on mercury electrodes but there is also a possibility of reducing them at lead, platinum or monel electrodes. The reduction of ethyl bromide at a lead cathode yields tetraethyl lead in a preparative reaction. Still, solid electrodes are usually not used for voltammetric measurements. 

Fields of Application. Although use of all halogen-containing substances is disputed, poly(vinyl chloride) still has a high rate of growth. 

---