Determination of traces of constituents with Schiff bases. Part IV. Extraction-spectrophotometric determination of copper with NN′-bis-salicylidene-2,3-diaminobenzofuran

Abstract

A selective method has been developed and is proposed for the spectrophotometric determination of microgram amounts of copper, after the extraction of copper(II) from an aqueous dioxan solution into benzene with NN′-bis-salicylidene-2,3-diaminobenzofuran.

Copper(II) reacts with this reagent to form an insoluble complex, which can be extracted quantitatively into benzene at a pH above 3·7. The complex extracted is stable and has an absorption maximum at 510 nm. Beer's law is obeyed over the range from 0 to 30 µg of copper. The molar extinction coefficient of the complex at 510 nm is 15,200 and the sensitivity for log (I₀/I)= 0·001 is 4·18 × 10^–3µg of copper cm^–2. The effect of some foreign ions has been examined, and only iron (III), tartrate and citrate interfered in the determination. The composition of the complex has been confirmed to be 1 : 1 and its structure has also been proposed.