Analysis of various very slightly water soluble drugs in micellar mediumII. Potentiometric and visual determination of sulphamethoxazole in pure for.
A potentiometric and/or visual method for the determination of sulphamethoxazole (SULF) in pure form in the range of 5.3 x 10(-5) to 5.0 x 10(-4) mol/L is proposed. To enhance the solubility, the determination has been carried out in a micellar medium formed by an aqueous 5.0 x 10(-2) mol/L N-hexadecyl-N,N,N-trimethyl ammonium bromide (CTAB) solution which increases the dissociation constant K(alpha) of SULF about tenfold. The titration is performed with NaOH (2.5 x 10(-3) or 5.0 x 10(-2) mol/L) and the end-point is determined by the second derivative graph. The results agree with those obtained by the official method of the USP XXIII. The method is simple, accurate, economical and can successfully replace the more complicated, more expensive and time-consuming existent procedures which are carried out in a non-aqueous medium.
Issopoulos
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Laboratory of Inorganic & Pharmaceutical Analytical Chemistry, Department of Chemistry, University of Ioannina, GR-451 10, Ioannina, Greece.