Ion-Association Complexes of Gallium(III)-4-(2-Pyridylazo)-resorcinol Anionic Chelates and Dicationic Tetrazolium Reagents

The formation and liquid-liquid extraction of ion-association complexes between gallium(III)-4-(2-pyridylazo)resorcinol (PAR) anionic chelates and cations of four ditetrazolium chlorides (DT2+) were studied:Neotetrazolium chloride (NTC), Blue Tetrazolium chloride (BTC), Nitro Blue Tetrazolium chloride (NBT) and Tetranitro Blue Tetrazolium chloride (TNBT). The optimum extraction-spectrophotometric conditions, composition of the extracted species {1:2:1 and/or 1:2:2 (Ga:PAR:DT)}, some equilibrium constants {constants of association (beta), constants of distribution (K-D) and constants of extraction (K-ex)} and analytical characteristics {molar absorptivity (epsilon), Sandell's sensitivity, intervals of adherence to Beer's law, etc.} were found. Relationships involving the number of nitro groups in DT2+ (N-nitro; DT2+ = BT2+, NBT2+ and TNBT2+) or molecular mass of DT2+ (MM; DT2+ = NT2+ and BT2+) were discussed: Log beta = f(N-nitro), Log K-D = f(N-nitro), Log K-ex = f(N-nitro), Log epsilon = f(N-nitro) and Log beta = f(Log MM).