Determination of Zinc, Cadmium, Lead and Copper in Kakade, Anise, Cumin, Caraway Black Pepper Extracts Using Differential Pulse Anodic Stripping Voltammetry with Hanging Mercury Drop Electrode

Abstract

An extraction and sensitive differential pulse anodic stripping voltammetric (DPASV) method at a hanging mercury drop electrode (HMDE) is described for the determination of Zn, Cu, Pb (mg g¹) and Cd (ng g¹) metal ions in water and 0.1 M HCl extracts for kakade, anise, cumin, caraway and black pepper. The procedure in water extract is based on the determination of four trace metal ions in presence of protein and carbohydrate at natural pH's. The extracted species in water extract acts as an electrolyte. The influence of extraction times on the content of proteins, carbohydrates and trace metal ions as well as pH values is demonstrated. DPASV could be able to determine Zn, Cd, Pb and Cu for kakade or Zn and Pb for anise in water extract in presence of 42 or 37% protein in dissolved organic matter (DOM). For cumin, caraway and black pepper, DPASV method could not be able to determine four metal ions in water extract in presence of 74-43% protein in DOM. Two wet digestion procedures (HNO3/H2O2 and HCl/H2O2) are applied to determine four metal ions in cumin, caraway and black pepper. Wet digestion process with HNO3/H2O2 efficiently destroys dissolved organic matter, thus enabling voltammetric measurements in presence of <19% protein. The proposed methods are shown to be applicable for Zn, Cd, Pb and Cu speciation before and after entering stomach