An-Najah Staff

Sensitive method for the determination of azathioprine by differential-pulse polarography (DPP) is described .  The cyclic voltammograms demonstrate the adsorption of the drug on the mercury electrode .  The effect of different experimental parameters affecting the drug determination e.g. pH, supporting electrolyte nature, accumulation potential, accumulation time, presence of copper ions and other operational parameters are also mentioned.  In pH 7.5, Britton-Robinson buffer, the calibration graph for the determination of azathioprine was linear in the range 5.0x10^-5 _- 5.0x10^-7 M with RSD of 1.3.  The detection limit was found to be 1.0x10^-8 M. The degree of interference from some other purines, anions and metal ions on the azathioprine peak was evaluated.  The method was applied to the determination of drug in commercially available dosage forms.

The voltammetric behaviour of methylated guanine-MeGua-(1-methylguanine, 3-methylguanine, 7-methylguanine and 9-methylguanine) was investigated over a wide pH range by using differential pulse cathodic stripping voltammetry at hanging mercury drop electrode. Methylated guanine as well as guanine are weakly interacted with mercury, but in presence of copper ions (5.0 × 10⁻⁷ M) they adsorb at a HMDE to give one stripping peak. This peak appears to be due to adsorption of MeGua-Cu(I) complex. The dependence of the stripping peak on the various experimental conditions is considered.

Cathodic stripping behaviour suggests that MeGua can be determined by cathodic stripping voltammetry in presence of Cu(II) ions and their detection limits are comparable to those for guanine.