Analytical uses of charge-transfer complexation: spectrophotometric method for iodide in water

Spectrophotometric determination of trace quantities of iodide after separation from large quantities of bromide, chloride, or sulfate by solvent extraction

“…If the molar absorptivity for TPI is assumed to be constant for the various chloroform extracts, and if its value is taken at 546 M_1 cm-1, then the percent recovery of iodide may be calculated by the expression ro r where As is the absorbance of salt solution containing added iodide, Ab is the absorbance of salt solution contain- 85.7 a 10.00-ml aliquot of iodide solution, 5.00 ml of CHCls, and 2.00 ml of 0.0428M TPHSO4. 6 Temperature of all runs was between 23 and 25 °C. c 2,4,6-Triphenylpyrylium perchlorate separated as a chloroform-insoluble solid.…”

“…Such techniques are rapid but they are not selective for the ion of interest and, therefore, suffer from interference in the presence of other extractable anions such as chloride, bromide, nitrate, perchlorate, and tetrafluoroborate. A novel method for the determination of aqueous iodide which is selective for iodide in the presence of chloride, bromide, and perchlorate ions has been described recently (6). After the addition of 4-cyano-lmethylpyridinium perchlorate to the aqueous iodide solution, the absorbance of the newly formed pyridinium-iodide ion pair was measured.…”

“…Determination of Total Iodide in Iodide-Iodate Mixtures0•6 No added salts other than sodium sulfite 6. Determinations made using standard curve for 10 3~described in text.…”

Ultraviolet spectrometry

“…Halogens and other anions may be determined as complexes. Chloride ion was determined as various mercury complexes (23,134), while iodide was determined as the 4-cyano-l-methylpyridinium charge-transfer complex (209). Cyanide ion was determined as the copper complex (99) and as the tetracyanonickelate complex (229).…”