Cloud point methodology was successfully employed for preconcentration of trace cobalt and nickel prior to their determination by flame atomic absorption spectrometry (FAAS). The metals react with 2-[2'-(6-methyl-benzothiazolylazo)]-4-bromophenol (Me-BTABr) in a surfactant Triton X-114 medium. Dilution of the surfactant-rich phase with acidified methanol was performed after phase separation, and the cobalt and nickel content was measured by FAAS. The proposed procedure allowed the determination of cobalt and nickel with detection limits of 0.9 and 1.1 mu gL(-1), respectively. The method was applied to metal determination in water samples. The validation of the procedure was carried out by analysis of a certified reference biological material, NIST 1570a Spinach Leaves. (c) 2006 Elsevier B.V. All rights reserved.