Differential-Pulse Polarographic Determination of Some N-Substituted Phenothiazine Derivatives in Dosage Forms and Urine Through Treatment with Nitrous Acid |
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Authors: | Fathalla Belal Saadia M El-Ashry Ihsan M Shehata Magda A El-Sherbeny Dina T El-Sherbeny |
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Institution: | (1) Department of Analytical Chemistry, Faculty of Pharmacy, University of Mansoura, Mansoura, 35516, Egypt, EG;(2) Department of Medicinal Chemistry, Faculty of Pharmacy, University of Mansoura, Mansoura, 35516, Egypt, EG |
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Abstract: | A highly sensitive differential-pulse (DPP) polarographic method is described for the determination of three N-substituted
phenothiazine derivatives, chlorpromazine (CZ), promazine (PZ) and promethazine (PMZ). The method involves the use of nitrous
acid as an oxidant. Polarographically-active sulphoxides with diffusion-current constants (Id) of 2.53, 3.05 and 3.37 were
obtained for CZ, PZ and PMZ, respectively. The polarographic waves were characterized as being diffusion-controlled, irreversible
and partly affected by adsorption phenomena. All parameters affecting the oxidation process and polarographic behaviour were
optimized and incorporated into the procedure. The limiting current-concentration plots in the DPP mode were rectilinear over
the range: 0.006–0.1 mM, 0.005–0.08 mM and 0.008–0.1 mM for CZ, PZ and PMZ, respectively, with minimum detectability (S/N=3)
of 3 × 10−7 M for CZ and PZ, and 4 × 10−7 M for PMZ, respectively. The kinetic parameters of the electrode reaction, including rate constant, free energy of activation
ΔG and effect of temperature on both parameters were studied. The proposed method was successfully applied to the determination
of phenothiazines in dosage forms; the results obtained were in agreement with those given with the official methods. The
method was further applied to the determination of promazine in spiked human urine. The percentage recovery was 96.86 ± 0.30.
The advantages of the proposed method over other reported methods were discussed. A proposal of the electrode reaction was
made.
Received June 1, 1999. Revision March 10, 2000. |
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Keywords: | : Chlorpromazine promazine promethazine nitrous acid urine polarography |
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