Application of Dipon, (1,4,8,11-Tetraazacyclotetradecane-4,11-bis(methylphosphonic acid) as Selective Complexing Agent for Determination of Copper(II)

Abstract

A new macrocyclic ligand, 1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid)(dipon), is selective complexing agent for copper(II) over other transition metal ions. The ligand was tested for analytical applications of copper(II) determination. Spectrophotometric determination under optimal experimental conditions (−log [H⁺]= 5.5, c _L≈ 5 × 10⁻⁴ mol L⁻¹, λ= 310 nm) is valid in dynamic range (5–200)× 10⁻⁶ mol L⁻¹ with detection limit 2.2 × 10⁻⁶ mol L⁻¹, i.e. 0.14 μg ml⁻¹. Volumetric determination of copper(II) with standardized dipon solution was used for copper(II) determination at micromolar concentration level without any necessity to sequester interfering metal ions. A sharp end point of titration was detected by UV/VIS spectrophotometry. Both methods were tested on artificial and real samples (spiked mineral water, alloys) and gave satisfactory results without any systematic error. The advantage of both methods is their simplicity, rapidity and no sensitivity to the presence of other metal ions.