Selective Kinetic Determination of Cu²⁺ with Tetraazamacrocyclic Bis(Methylphosphonate) Ligand (Dipon)

Abstract.

A new macrocyclic ligand, 1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) (refered to as dipon) exhibits high thermodynamic and kinetic selectivity for Cu²⁺ compared to other transition metal ions. The initial-rate method (λ = 310 nm, pH = 3.75, c_L≈4.6×10⁻³ mol L⁻¹) was chosen as an optimal experimental approach in order to achieve maximum sensitivity of determination. The dynamic range of the method is (5–200)×10⁻⁶ mol L⁻¹, and the detection limit is 2.5 × 10⁻⁶ mol L⁻¹. A standard addition procedure was applied to the kinetic determination of Cu²⁺ to eliminate the effect of interfering ions (e.g. Zn²⁺, Ca²⁺, Mg²⁺, Cd²⁺, Pb²⁺, Mn²⁺, Co²⁺, Ni²⁺, HCO⁻₃, Cl⁻, SO₄²⁻, etc.). The method was tested on artificial and real samples (alloys, pure and spiked mineral water) and gave satisfactory results which are in agreement with the values for some certified materials. The advantage of the proposed method is rapidity, simplicity and robustness in the presence of other metal ions.