Quantitative separation of zinc traces from cadmium matrices by solid-phase extraction with polyurethane foam

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Accurate determination of zinc requires effective separation from interfering elements like cadmium.
• Solid-phase extraction offers a promising technique for selective analyte isolation.

Purpose of the Study:

• To develop and optimize a solid-phase extraction method for separating zinc traces from large amounts of cadmium.
• To investigate the efficiency and selectivity of polyurethane foam for zinc thiocyanate complex extraction.

Main Methods:

• Solid-phase extraction using polyurethane foam (PU foam).
• Optimization of pH, thiocyanate concentration, and shaking time for zinc extraction.
• Investigation of interfering ions and development of selective back-extraction procedures.
• Application of the method for zinc determination in cadmium salts using spectrophotometry.

Main Results:

• Optimal zinc extraction achieved at pH 3.0 ± 0.50 with 0.15–0.20 mol L⁻¹ thiocyanate and 5 min shaking time.
• Effective separation from various cations (Ca, Ba, Sr, Mg, Al, Ni, Fe(II)) and anions (nitrate, chloride, sulfate, etc.).
• Selective extraction enhanced by ascorbic acid for Fe(III) reduction and citrate for masking Cu(II) and Co(II).
• Quantitative zinc back-extraction achieved by shaking with water for 10 min.
• Method validated against ICP-AES for zinc determination in cadmium salts with comparable accuracy and precision.

Conclusions:

• Polyurethane foam solid-phase extraction provides an efficient and selective method for separating zinc from cadmium.
• The optimized method is robust, handles various interfering ions, and is suitable for trace zinc determination in complex matrices.