Voltammetric determination of nitrosocimetidine in simulated gastric juice

OBJECTIVE

To develop a voltammetric method for the determination of nitrosocimetidine in simulated gastric juice (SGJ).

METHOD

Measurement of the polarographic wave of the nitroso derivative at the dropping mercury electrode in 0.1 m HCl.

RESULTS

A well-defined diffusion-controlled cathodic wave was obtained at -0.34 V vs. Ag/AgCl electrode. The current-concentration relationship was found to be rectilinear over the range 10-80 microg/mL and 2-50 microg/mL with percentage recovery of 101.24 +/- 0.79 and 100.79 +/- 0.56 for the direct current (DCt) and differential pulse polarography (DPP) modes, respectively, with a minimum detectability (S/N=2) of 0.16 microg/ml (5.6 x 10-7 m) using DPP mode.

CONCLUSION

The proposed method was successfully applied to study the nitrosation of cimetidine in SGJ.

Voltammetric determination of isoxsuprine and fenoterol in dosage forms and biological fluids through nitrosation

A simple and highly sensitive voltammetric method was developed for the determination of isoxsuprine HCl (I) and fenoterol HBr (II) in dosage forms and biological fluids. The method is based on treatment of the two compounds with nitrous acid followed by measuring the cathodic current produced by the resulting nitroso derivatives. The voltammetric behavior was studied adopting Direct Current (DCt), Differential Pulse (DPP) and Alternating Current (ACt) polarography. Both compounds produced well-defined, diffusion-controlled cathodic waves over the whole pH range in Britton-Robinson buffers (BRb). At pH 11 and pH 9, the values of diffusion-current constants (Id), were 9.4 +/- 0.3 and 7.7 +/- 0.4 for I and II, respectively. The current-concentration plots for I were rectilinear over the range of 0.6-12 microg/ml and 0.1-12 microg/ml in the DCt and DPP modes, respectively. As for II, the range was 1-20 microg/ml and 0.1-20 microg/ml in the DCt and DPP modes, respectively. The minimum detectability (S/N = 2) were 0.02 microg/ml (approximately 6 x 10(-8) M) and 0.01 microg/ml (approximately 2.6 x 10(-8) M) for I and II, respectively, adopting the DPP mode. The proposed method was applied to the determination of both compounds in dosage forms and the results obtained were in good agreement with those obtained using reference methods. The proposed method was further applied to the determination of isoxsuprine in spiked human urine and plasma. The percentage recoveries adopting the DPP mode were 98.84 +/- 1.18 and 99.26 +/- 0.97, respectively.

Voltammetric determination of N,N'-dinitrosopiperazine in simulated gastric juice

A voltammetric method has been developed for the determination of N,N'-dinitrosopiperazine (DNPZ) in simulated gastric juice. The method is based on measuring the differential pulse polarographic peak produced in pH 3 Britton Robinson buffer. A well defined, diffusion-controlled cathodic wave was obtained at -0.77 V versus Ag/AgCl over the range 0.4-24 microg/ml with minimum detectability (S/N = 2) of 0.072 microg/ml (5 x 10(-7) M). The proposed method was successfully applied to study the possible in vivo production of the nitroso-derivatives of piperazine under the standard nitrosation reaction conditions recommended by WHO. The method has some distinct advantages over the reported GC methods.