Photometric determination of copper (II) microquantities in pyrite

Abstract

4-(2, 4-bis((2-aminoethyl)-imino)pentane-3-yl)diazenyl)benzoic acid was synthesized using 3-[4-carboxyphenylazo]pentanedione-2,4 (R) reagent obtained by the standard procedure. The composition and structure of the synthesized reagent is determined by the methods of elemental analysis and NMR spectroscopy. The complexation of copper (II) with 3-[4-carboxyphenylazo]pentanedione-2,4 (R) in the presence and in the absence of 8-hydroxyquinoline, diphenylguanidine and ethylenediamine was studied spectrophotometrically. Optimal conditions for complexation are specified and composition of homo- and mixed-ligand complexes are determined. When copper (II) interacts with R at pH 3 – 10, the maximum yield of the complex compound is observed at pH 5 λ max = 553 nm. The molar absorption coefficients and the stability constants of copper (II) complexes were determined. A range in which Beer’s law is valid is determined. Study of the complex with 8-hydroxyquinoline (Ox), diphenylguanidine (DPG) and ethylenediamine (ED) present showed that under the effect of these compounds, the optical density of the complex solutions significantly increases and the pH value of the medium providing optimal complexing shifts to the acidic region: pH 2 – 3. The maxima of the absorption of mixed-ligand complexes are observed at λ = 564 nm (CuR 2 -Ox), λ = 568 nm (CuR 2 -DFG), λ = 576 nm (CuR 2 -Ed). Comparison of the values of the stability constants of homo- and mixed-ligand Cu (II) complexes shows that CuR 2 -ED is more stable than the other ones under study. The effect of foreign ions and masking substances on complexation was studied. The selectivity of the obtained reagent for copper (II) determination, compared to the reagents of the same duty known from the literature appeared advantageous. The high selectivity of the studied reactions provided developing of a rapid method for copper determination in rocks. A procedure for the spectrophotometric determination of copper (II) in pyrite is developed.