Voltammetric determination of N-nitrosoderivatives of atenolol and propranolol in simulated gastric juice

A highly sensitive and simple voltammetric method is proposed for the determination of N-nitrosoatenolol (NA) and N-nitrosopropranolol (NP) in simulated gastric juice. The method is based on measuring the differential-guise polarographic peak produced by NA and NP in Britton-Robinson buffers of pH 3 and 4 for NA and NP, respectively. Both compounds yielded diffusion-controlled current with diffusion-current constants of 7.23 +/- 0.03 and 9.46 +/- 0.06 for NA and NP, respectively. The current-concentration plots were rectilinear over the range 0.16-9.6 mu g ml(-1) with minimum detectability (S/N = 2) of 0.015 mu g ml(-1) (5 x 10(-8) M) for NA; for NP the range was 0.08-8.0 mu g ml(-8) with minimum detectability (S/N = 2) of 0.009 mu g ml(-1) (3 x 10(-8) M). The proposed method was successfully applied to study the possible in vivo production of the nitroso-derivatives under the standard nitrosation reaction conditions recommended by WHO. The method is characterized by simplicity and higher sensitivity as compared with the reported HPLC method. (C) 1999 Elsevier Science S.A. All rights reserved.