Phenylmethoxybis(tetrazolium) ion-association complexes with an anionic indium(III) - 4-(2-pyridylazo)resorcinol chelate

摘要

Received 8 July 2012; Accepted 4 October 2012 Complex formation and liquid-liquid extraction were studied in systems containing indium(III), 4-(2-pyridylazo)resorcinol (PAR), phenylmethoxybis(tetrazolium) salt (MBT), water and chloroform. The following MBTs, which differ only by the number of -NO2 groups in their cationic par ts, were used: 3,3'-(3,3'-dimetoxy-4,4'-biphenylene)bis(2,5-diphenyl-2H-tetrazolium chloride) (Blue Tetrazolium chloride, BT), 3,3'-(3,3'-dimetoxy-4,4'-biphenylene)bis[2-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride] (Nitro Blue Tetrazolium chloride, NBT) and 3,3'-(3,3'-dimetoxy-4,4'-biphenylene)bis[2,5-di(4-nitrophenyl)-2H-tetrazolium chloride] (Tetranitro Blue Tetrazolium chloride, TNBT). The composition of the formed ternary complexes was determined, In:PAR:MBT=1:2:2, and the optimum conditions for their extraction found: pH, shaking time, concentration of the reagents and the sequence of their addition. Some key constants were estimated: constants of extraction (K_(ex) ), constants of association (β) and constants of distribution (KD). BT appears to be the best MBT for extraction of the In(III)-PAR species, [In3+(OH)3(PAR)2]~(4-), (Log K_(ex) =10.9, Log β=9.8, Log KD=1.12, R%=92.7%). Several additional characteristics concerning its application as extraction-spectrophotometric reagent were calculated: limit of detection (LOD = 0.12 μg cm~(-3) ), limit of quantifcation (LOD = 0.40 μg cm~(-3) ) and Sandell's sensitivity (SS =1.58 ng cm~(-2) ); Beer's law is obeyed for In(III) concentrations up to 3.2 μg mL~(-1) with a molar absorptivity coeffcient of 7.3×104 L mol~(-1) cm~(-1) at λ =515 nm.