6-Methyl-2-pyridinecarboxamide oxime, a reagent for copper

6-Methyl-2-pyridinecarboxamide oxime (R) forms a yellow compound with copper(I), the molar absorptivity being 7.2 x 10(3) at the wavelength of maximum absorption, 405 nm. The copper compound, CuR(2), forms completely over the pH range 4.5-7 and is easily extracted into isoamyl alcohol. R is highly specific for copper, the methyl group neighbouring the ring nitrogen atom preventing reaction with iron and other metals.