Phenanthroline (phen) was tested as a complexing agent for on line preconcentration of iron on RP C-{18} material in a microcolumn with flow injection coupled with flame atomic absorption spectrometer (FI FAAS). The on line formed Fe(II) phen complexes were adsorbed on the C-{18} sorbent material. Various parameters affecting the on line Fe(II) phen complex formation and its subsequent adsorption in the microcolumn as well as its elution into the nebulizer of AAS were optimized. A 2.5×10+{-3} mol/L phen in 2% ethanol was on line mixed with aqueous sample solution acidified with 0.1% (v/v) HCl and allowed to flow through the microcolumn for 30 s. The adsorbed Fe(II) phen complexes in the microcolumn were eluted with ethanol in 10 s into the nebulizer of AAS. Ascorbic acid (5×10+{-4} mol/L) was added to the sample solution for the reduction of Fe(III) to Fe(II). A good precision (RSD=1.1%, %n%=10), high enrichment factor (19) and sample throughput (90 h+{-1}) with detection limit (3σ) of 3 μg/L were obtained. The method was applied on standard reference materials(i.e. mussel and tomato leaves,) for iron determination and yielded results agreeing well with certified values. Phenanthroline (phen) was tested as a complexing agent for on line preconcentration of iron on RP C - {18 } material in a microcolumn with flow injection coupled with flame atomic absorption spectrometer (FI FAAS). The on line Various parameters affecting the on line Fe (II) phen complex formation and its subsequent adsorption in the microcolumn as well as its elution A 2.5 × 10 + {-3 } mol / L phen in 2% ethanol was on line mixed with aqueous sample solution acidified with 0.1% (v / v) HCl and The adsorbed Fe (II) phen complexes in the microcolumn were eluted with ethanol in 10 s into the nebulizer of AAS. Ascorbic acid (5 × 10 + {- 4 } mol / L) was added to the sample solution for the reduction of Fe (III) to Fe (II). A good precision (RSD = 1.1%, % n % = 10) ) and sample throughput ( The method was applied on standard reference materials (ie mussel and tomato leaves,) for iron determination and yielded results. 90 h + {- 1 }) with detection limit (3σ) of 3 μg / agreeing well with certified values.