Nickel was determined by the conventional flame atomic absorption spectrometry (FAAS) at the upper trace range. The absorbance was measured for a wide range of concentration (10-100 mgL-1) at the resonance lines 232.0 and 352.34 nm for nickel. Using ordinary least square fitting, the calibration curve corresponding to the measured absorbance with the corresponding concentration was constructed for each line. Based on straight line regression, the measurements were validated by calculating the limit of detection (LOD) for the two nickel lines under investigation. The effect of self-absorption on the measured absorbance was studied. A simple method was developed in order to estimate quantitatively the self-absorption effects for the resonance lines of nickel by means of the escape factor. The reliability of the escape factor method was verified by providing calibration curves of some environmental elements Na, Ca, Cd and Zn. The results obtained for the limit of detection (LOD) for the elements under consideration were compared with those found in literature