Development of spectrophotometric method for iron determination in fortified wheat and maize flours

• Published in: Food chemistry 2018-03, Vol.242, p.205-210
• Main Authors: de Oliveira e Silva, Ana Flávia, de Castro, Whocely Victor, de Andrade, Frank Pereira
• Format: Article
• Language: English
• Subjects: Cloud point extraction; Flour - analysis; Food, Fortified - analysis; Iron - analysis; Iron determination; Limit of Detection; Method validation; Molecular UV-VIS spectrophotometry; Spectrophotometry - methods; Triticum - chemistry; Wheat and maize flours; Zea mays - chemistry
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2017.08.110

•The method shows sensitivity, effortlessness and feasibility.•The development of the method was conducted by 24 factorial design with central point.•The method was validated by determination of Fe2+ in fortified flours.•The square root of absorbance was applied to adjust the linearity.•The concentration of Fe2+ in fortified flours is in the order of µgg−1. The determination of iron in fortified foods is mandatory by many global regulatory agencies. However, the spectroscopic techniques require elevated investments limiting their applicability especially in developing countries. Therefore, simple, viable and analytical methods with sufficient sensitivity can become an alternative. In this work, a sensitive, simple and viable spectrophotometry method to determine iron in wheat and maize flours was developed following a cloud point extraction (CPE) procedure. The analyte was first complexed with 2-(5-Bromine-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) in the presence of the surfactant octylphenoxypolyethoxyethanol (Triton X-114). For the CPE optimization the variables: pH of the medium, stoichiometry of the complex, surfactant, and salt concentrations were evaluated. Linearity in the analytical blank was obtained by using the square root of absorbance (Abs) in order to adjust the residues of the curve. The precision was lower than 5% and the accuracy ranged from 97 to 101%. The limits of detection and quantification were 0.004μgmL−1 and 0.01μgmL−1, respectively. The method was applied to investigate the content of iron in 14 brands of fortified flours. The concentrations of iron varied from 0.435 to 3.62mg/100g and 0.570 to 3.15mg/100g in wheat and maize flour, respectively. The content of iron in all brands investigated in this study was approximately 10-fold lower than the value required by (ANVISA). The amount of iron in fortified foods was satisfactorily determined by using a simple, sensitive, and low cost spectrophotometric method.