Determination of total iron in water and foods by dispersive liquid–liquid microextraction coupled with microvolume UV–vis spectrophotometry

• Published in: Food chemistry 2015-06, Vol.176, p.288-293
• Main Authors: Peng, Bo, Shen, Yingping, Gao, Zhuantao, Zhou, Min, Ma, Yongjun, Zhao, Shengguo
• Format: Article
• Language: English
• Subjects: 5-Br-PADAP; Colorimetry; Dispersive liquid–liquid microextraction; Food Analysis - methods; Foods; Hydrogen-Ion Concentration; Iron; Iron - analysis; Joining; Limit of Detection; Liquid Phase Microextraction - methods; Phenol; Reduction; Solvents; Spectrophotometry; Spectrophotometry, Ultraviolet - methods; UV–vis spectrophotometry; Water - analysis
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2014.12.084

•The selectivity of the iron detection can be greatly enhanced at wavelength 740nm.•The present method has a good sensitivity with a detection limit of 1.5μgL−1.•The present method has a wider linear range in compared with other method reported.•The UV–vis detection with DLLME for Fe is simple, rapid and economical. A novel microvolume UV–vis spectrophotometry method was proposed for the rapid determination of total iron coupling with an efficient pretreatment method known as dispersive liquid–liquid microextraction (DLLME). The basis of the method is a quantitative colorimetric reaction between ferrous iron and 2-(5-bromo-2-pyridylazo)-5-(diethyl amino) phenol (5-Br-PADAP) after the reduction of Fe(III) to Fe(II) by using ascorbic acid as reducing agent. Parameters related to the efficiency of microextraction, such as pH, complexant concentration, the volume ratio of disperser solvent and extraction solvent were discussed and optimized in detail. Under the optimized conditions, the absorbance was in proportion to iron concentration in the range of 5–400μgL−1 with a correlation coefficient (R) of 0.9993. The limit of detection (LOD) and limit of quantitation (LOQ) were 1.5μgL−1 and 5.2μgL−1, respectively. The relative standard deviation (RSD) for samples were 1.37– 4.42% (n=3). Good recoveries of iron were obtained in the range of 95.4–103.2% in food samples, 96.9–103.6% in water samples and 98.8–102.3% in Certified Reference Material. The proposed method was rapid, reliable and high-selective for the determination of total iron in food and water samples.