Study of the influence of interfering ions of heavy metals and various sample preparation on the determination of mercury impurity in protamine sulfate by stripping voltammetry
Aim. To determine the content of mercury in protamine sulfate samples with different sample preparation. To study the effect of interfering ions on the content of mercury impurity in protamine sulfate by stripping voltammetry (SV). Materials and methods. We used a solution for injection of protamine sulfate, batches 515091, 514062, 514111; for sample preparation - various options for dilution and precipitation. Dilution was carried out with bidistilled water, and the precipitation of proteins - with sodium tungstate in 2 options. Mercury impurities were determined by the SV method. Results. The mercury content in protamine sulfate samples was 0.000417 ± 0.00140 and 0.000420 ± 0.00152 mg/l when diluted with water 1 : 2 and 1 : 1 respectively and 0.000462 ± 0.00131 and 0.000459 ± 0.00121 when precipitated with tungstate in options 1 and 2 respectively. With the addition of an interfering ion, for example, Cu<sup>2+</sup>, the content of mercury in the medicinal product was 0.000606 ± 0.00015, 0.000452 ± 0.00013 and 0.0004212 ± 0.00011 mg/l for protamine sulfate batches 514062, 515091 and 514111 respectively, which does not exceed the values determined by the product specification. The addition of Pb<sup>2+</sup>, Fe<sup>2+</sup>, Zn<sup>2+</sup>, Cu<sup>2+</sup>, and Cd<sup>2+</sup> ions also had no effect on the determination of the mercury content in protamine sulfate samples. Conclusion. To determine the mercury impurity in the protamine sulfate, special sample preparation is not required. Ions of Cu<sup>2+</sup>, Pb<sup>2+</sup>, Fe<sup>2+</sup>, Cd<sup>2+</sup>, Zn<sup>2+</sup> do not affect the result of determining the mercury content in protamine sulfate samples by the SV method, which indicates a high selectivity of the method used.