Abstract: Adirect, rapid and sensitive method for the determination of Fe(Ⅱ) and Fe(Ⅲ) in water samples by flame absorption spectrometry coupled with flow injection on line preconcentration with 1,10-phenanthroline(1,10-phen) as the complex agent was developed. Various parameters affecting the complex formation and its subsequent adsorption, such as pHof the mixture solution, 1,10 phen concentration, sample flow rate etc. were optimized. A 25×10^-3 mol/L 1,10 phen in 2.0% ethanol was on line mixed with aqueous sample solution of iron in 0.1%(volume ratio) hydrochloric acid and flowed through the microcolumn for 30 s. Fe(Ⅱ) can be extracted as Fe(Ⅱ)-phen complex in the C₁₈ microcolumn and determined within 10 s in the nebulizer of FAASafter being eluted by ethanol. Ascorbic acid(0.1 mg/mL) was used for the reduction of Fe(Ⅲ) to Fe(Ⅱ). Agood precision(RSD=1.1%, n =10), high enrichment factor(19) and sample throughput(80 h) with detection limit 3 μg/Lwere obtained. The method has been successfully applied on the water sample for Fe(Ⅱ) and Fe(Ⅲ) determination with the recovery 94%—105%.

Key words: Flow injection analysis, Flame atomic absorption spectrometry, On line preconcentration, Fe(Ⅱ),Fe(Ⅲ)