Dimethylglyoxime (DMG) has been tested as a complexing agent for the determination of nickel after online preconcentration on RP-C 18 in a microcolumn using flow injection coupled with a flame atomic absorption spectrometry system (FI-FAAS). The Ni-DMG complexes formed online can be adsorbed on the C 18 sorbent. Various parameters affecting the online Ni-DMG complex formation and its subsequent adsorption in the microcolumn as well as its elution into the nebulizer of the FAAS were optimized. A 10 ฯช3 mol/L solution of DMG in 4% ethanol was mixed online with an aqueous sample solution acidified to 0.1% (v/v) nitric acid and flowed for 30 s through the microcolumn. The adsorbed Ni-DMG complex in the microcolumn was eluted with ethanol containing 1% HNO 3 into the nebulizer of the FAAS in 10 s. A good precision (RSD ฯญ 1.7%, n ฯญ 14), high enrichment factor (21), and high sample throughput (90 h ฯช1 ) with detection limit (3) 3 g/L were obtained. The method was applied to standard reference materials, i.e., NBS-362, NBS-364 (special low-alloy steel), and mussel (GBW 08571), for the determination of nickel and the results were in good agreement with certified values. Nickel recovery from seawater and high-purity magnesium oxide in the range 98 -100% can be obtained by this method.