Voltammetric determination of zinc in compound pharmaceutical preparations--validation of method.

The conditions of voltammetric determination of zinc in compound pharmaceutical preparations were established and validated. The three investigated preparations (Organic zinc (A), Calcium, zinc, copper with vitamin C (B), Vigor complete (V) contained different salts of zinc (II) and increasing number of other components. The samples of powdered tablets of each preparation were undergone mineralization or extraction procedures for the purpose to transfer the zinc ions into solution. The concentration of zinc in solution was determined by differential pulse voltammetry (DP). The selectivity, accuracy, precision and linearity of DP determination of zinc in three preparations were estimated in validation process. Zinc was determined within the concentration range of 1-12 ppm (1-12 microg/mL): the mean recoveries approached 96-99% (A), 96-102% (B), 106% (V); the relative standard deviations of determinations (RSD) were 2,97-2,98% (A), 2,83-3,84% (B) and 2,65% (V). The mean recoveries and the errors of determination satisfied the requirements for the analyte concentration at the level 1-20 ppm (12).