USE OF A FLATBED SCANNER AND POLYURETHANE FOAM FOR QUANTIFICATION OF TOTAL IRON IN FOOD SUPLEMENTS

In this work, an alternative and low-cost technique for the extraction and quantification of Fe (total) from food supplements by digital image analysis is shown. The method is based on the complexation of Fe ions in solution with the 8-hydroxyquinoline ligand, forming a colored complex that is extractable from aqueous solution to polyurethane foam, coloring this one, which was initially white, to brown. After the acquisition and treatment of the digital image generated by the foam, the quantification of Fe is performed. Interference and recovery tests show that the method is not affected by concomitants in the sample. The method was applied to 3 different types of dietary supplements, and these results were compared to those obtained by FAAS, showing statistical equivalence. The limits of quantification obtained in this work was 1.78 µmol L-1, the limit of detection was 0.53 µmol L-1, the accuracy was 97.5 + 4.8% and the precision was 8.45%. The analytical curve was linear from 2.0 to 10.0 µmol L-1, with a r2 of 0.9975.本研究提出了一种基于数字图像分析的低成本替代方法，用于从食品补充剂中提取并定量测定总铁（Fe）。该方法基于溶液中铁离子与8-羟基喹啉（8-hydroxyquinoline）配体的络合反应，生成有色络合物；该络合物可从水溶液中萃取至聚氨酯泡沫（polyurethane foam）中，使原本呈白色的聚氨酯泡沫变为棕色。对该泡沫生成的数字图像进行采集与处理后，即可完成铁元素的定量测定。干扰与回收实验结果表明，本方法不受样品中共存杂质的影响。本方法应用于3种不同类型的膳食补充剂，将所得结果与火焰原子吸收光谱法（FAAS）的测定结果进行对比，二者表现出统计学上的等效性。本研究得到的定量限为1.78 µmol L⁻¹，检出限为0.53 µmol L⁻¹，准确度为97.5 ± 4.8%，精密度为8.45%。分析曲线在2.0~10.0 µmol L⁻¹范围内呈线性关系，决定系数r²为0.9975。