Abstract
Cerium(IV) sulfate oxidizes 10-[3′-[N-bis(hydroxyethyl)amino]propyl]-2-chlorophenoxazine [BPCP] reversibly to a pink-colored radical cation [BPCP+·] in the presence of stoichiometric amounts (BPCP:Ce(IV) = 1:1) of the reactants. The radical cation underwent a second one-electron oxidation to form a brownish yellow-colored dication [BPCP2+] in the presence of more than one equivalent of Ce(IV), which was characterized by IR, mass-spectral and UV-vis spectroscopy. The cyclic voltammogram of BPCP exhibited two reversible anodic waves at 640 mV and 1057 mV and two cathodic waves at 582 mV and 930 mV at a scan rate of 24 mV/s. The peak at 640 mV corresponds to the oxidation of BPCP to the radical cation [BPCP+·] and the second anodic peak at 1057 mV stands for the oxidation of the radical cation to dication [BPCP2+]. Bromine oxidized BPCP to three products, as evidenced by HPLC. The tentatively predicted structures based on the mass-spectral data support the formation of brominated oxidized products. The respective first and second formal potentials of BPCP were found to be 782 mV and 936 mV and the transition potential of BPCP in the tritration of ascorbic acid with N-bromosuccinimide was found to be 787 mV in 0.5 M sulfuric acid. The optimum conditions for the use of BPCP as a redox indicator in the macro and micro determination of ascorbic acid, methionine, isoniazid, phenylhydrazine hydrochloride and biotin using N-bromosuccinimide as an oxidant have been developed.
