MultiSimplex optimization of on-line sorbent proconcentration and determination of iron by FI-AAS and microcolumn of immobilized ferron

A simple flow injection on-line separation and proconcentration system for determination of iron in milk and water samples were developed. Ferron was physically immobilized on alumina particles in the pH range of 2.5–6 and was used as sorbent in microcolumn preparation. Deposition of iron was effected by processing a standard or solution of analyte at pH range of 3–6 on the microcolumn. Injection of 300 μl of HNO3 (5 mol l−1) served to elute the retained species to FAAS. Different factors affecting the performance of the system were optimized by MultiSimplex and univariable methods. MultiSimplex program based on the simplex algorithm allowed the simultaneous study of the variables affecting immobilization, sorption or elution process. The capacity of the sorbent under working condition was found to be 989.0 μg irons per gram of packing material. A sample volume of 20 and 40 ml resulted in preconcentration factors of 65 and 129, respectively. Precision (n = 6) at 125 and 50 μg l−1 were 2.0 and 2.9%, respectively. With 20 ml sampling volume a detection limit of 1.06 μg l−1 was determined. The method was applied to determination of iron in tap water, river water, rain water, spring water, infant dry formula milk, human and cow milk. The accuracy was assessed through recovery experiments, independent analysis by furnace atomic absorption, and analysis of certified reference alloy.