A spectrometric and first derivative spectrometric determination of copper (II) is carried out with 1-nitroso-2-naphthol as complexing reagent in aqueous phase using non-ionic surfactant Tween 40. The copper is determined in the range 1.7-120 ng ml-1 with detection limit (2α) of 1.7ng/ml-1. The molar absorptivity and sandell’s sensitivity are 1.90 x (104 mol-1cm-1) and 7.9ng cm-2 at 483.5 nm. The optimum pH of the complex is 9. The critical micelle concentration (cmc) of Tween 40n is 5%. Absorption a studies in the first derivative mode is carries out to determine the absorption maximum of the complex for higher sensitivity and to overcome interference due to presence of certain metal ions. The present’s method is compared with that of AAS and no sufficant difference is noted between the two methods at 95% confidence level. The method has been applied for the determination of Cu(II) in industrial waste samples.