Simple, selective, and sensitive spectrophotometric method for determination of trace amounts of nickel(II), copper(II), cobalt(II), and iron(III) with a novel reagent 2-pyridine carboxaldehyde isonicotinyl hydrazone

A selective and sensitive reagent of 2-pyridine carboxaldehyde isonicotinyl hydrazone(2-PYAINH) was synthesized and studied for the spectrophotometric determination of nickel, copper, cobalt, and iron in detail. At a pH value of 7.0, 9.0, 9.0, and 8.0, respectively, which greatly increased the selectivity; nickel, copper, cobalt, and iron reacted with 2-PYAINH to form a 1:2 yellow-orange, 1:2 yellow-green, 1:2 yellow and 1:1 yellow complexes, with absorption peaks at 363, 352, 346, and 359 nm, respectively. Under the optimal conditions, Beer's law was obeyed over the ranges of 0.01-1.4, 0.01-1.5, 0.01-2.7, and 0.01-5.4 mg/L, respectively. The apparent molar absorptivity and Sandell's sensitivities were 8.4x10(4), 5.2x10(4), 7.1x10(4), and 3.9x10(4) L center dot mol(-1)center dot cm(-1), respectively, and 0.00069, 0.0012, 0.00078, and 0.0014 mu g center dot cm(-2), respectively. The detection limits were found to be 0.001, 0.002, 0.003, and 0.01 mg/L, respectively. The detailed study of various interfering ions to make the method more sensitive was carried out and selective and several real samples were analyzed with satisfactory results.