Extraction-spectrophotometric determination of nickel in steels and aluminium metal with 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine and ethyl tetrabromophenolphthalein

Abstract Nickel ions react with 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine in aqueous solution at pH 6.8 to form a red 1:3 complex cation which can be extracted at pH 6.3 into 1,2-dichloroethane with ethyl tetrabromophenolphthalein anion as an ion association compound having an absorption maximum at 610 nm. The apparent molar absorptivity is 2.21 × 10 5 l mol −1 cm −1 and a linear calibration graph is obtained in the range 0–0.05 μg ml −1 (0−8.52 × 10 −7 M) nickel in aqueous solution. The r.s.d, is 1.5%. This method can be applied to the determination of traces of nickel in steels and aluminium chips.