Nickel is quantitatively retained on 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP)–ammonium tetraphenylborate with microcrystalline naphthalene or by a column method in the pH range 9.0–10.5 from a large volume of aqueous solutions of various samples. After filtration, the solid mass consisting of the nickel complex and naphthalene was dissolved with 5 ml of dimethylformamide and the metal was determined by atomic absorption spectrometry. The nickel complex can alternatively be quantitatively adsorbed on ammonium tetraphenylborate–naphthalene adsorbent packed in a column and determined similarly. The calibration curve is linear at 0.30–18 ppm in dimethylformamide solution. Eight replicate determinations of 5.0 ppm of nickel gave a mean absorbance of 0.096 with a relative standard deviation of 1.5%. The sensitivity for 1% absorption was 0.23 µg ml–1. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for the trace determination of nickel in various standard samples.