Solid-liquid separation after liquid-liquid extraction: spectrophotometric determination of copper by extraction of its 1-phenyl-4,4,6-trimethyl-(1H,4H)-pyrimidine-2-thiol into molten naphthalene

A selective spectrophotometric method has been developed for the determination of copper after extraction of its 1-phenyl-4,4,6-trimethyl-(1H,4H)-pyrimidine-2-thiol (PTPT) complex into molten naphthalene. The optimum pH range for the extraction is 7.4–11.7. The solid naphthalene containing the copper - PTPT complex is separated by filtration and dissolved in chloroform. The absorbance is measured at 400 nm against a reagent blank. Beer's law is obeyed in the concentration range 5.0–60.7 µg of copper in 10 ml of chloroform solution. The molar absorptivity and sensitivity are 1.23 × 104 1 mol–1 cm–1 and 0.008 11 µg cm–2, respectively. The interference of various ions has been studied in detail. Conditions have been established for the determination of copper in goat liver, human hair and certain alloys.