Extraction spectrophotometric determination of quaternary ammonium salts utilizing ternary ion associate formation with cinchona-alkaloids and tetraiodofluorescein

Tetraiodofluorescein (TIF) reacts with quinine(Qn) to form TIF2-(Qn(+))(2) at pH 7.0, and the color of the associate develops in 1,2-dichloroethane. When trace amounts of quaternary ammonium salts, such as cetylpyridinium chloride and trimethylstearylammonium chloride, are added to the TIF-Qn extraction system, the extractability of the associate is enhanced. It is assumed that new ternary ion associates, TIF2-.Qn(+).CPC+, are formed at pH 9.0. Although the molar absorptivity of TIF-CPG associate at pH 6.8 is about 2.5 x 10(4) I mol(-1) cm(-1), that of the ternary ion associate with Qn is 8.0 x 10(4)I mol(-1) cm(-1) It is possible to determine quaternary ammonium salts at the 10(-7) mol/l level using this method. Various amines do not interfere in the extraction system.