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 (KD and constants of extraction (Kex)} 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+ (Nnitro; DT2+ = BT2+, NBT2+ and TNBT2+) or molecular mass of DT2+ (MM; DT2+ = NT2+ and BT2+) were discussed: Log beta =f(Nnitro), Log KD =f(Nnitro), Log Kepsilon=f(Nnitro), Log epsilon =f(Nnitro) and Log beta = f(Log MM).