Determination Of Total Iron In Water And Food Samples By Dispersive Liquid-Liquid Microextraction And Digital Image Colorimetric Analysis

Dispersive liquid-liquid microextraction has been widely applied for separation and pre-concentration of trace level metals in various samples due to high enrichment,convenient operation and low cost. In this thesis, dispersive liquid-liquid microextraction combined with microvolume UV-Vis spectrophotometry and digital image colorimetric method were used to determine the total iron in food and water samples. The widely used mobile phones and portable scanner were excellent devices for assisting making fast visual detection. The main contents are given as follows:Chapter 1: The principle, the influencing factors, the development and application of the dispersive liquid-liquid microextraction technique were reviewed in this chapter. The digital image colorimetric analysis and its application were surveyed in detail. The commonly used color space in chromatology were introduced and summarized. The fast analysis based on ordinary smart phone in biomedical and analytical chemistry were well reviewed.Chapter 2: In this part, a dispersive liquid-liquid microextraction method combined with microvolume UV-Vis specrophotometry was established for the rapid determination of total iron using 5-Br-PADAP as the complexing reagent. Parameters related to the efficiency of microextraction, such as p H, the type and volume of extraction and disperser solvent and the concentration of reagent were discussed and optimized. Under the optimized conditions, the absorbance was in proportion to iron concentration in the range of 5.2-400 μg/L with a correlation coefficient of 0.9982. The limit of detection(LOD) and limit of quantitation(LOQ) were 1.5 μg/L and 5.2 μg/L, respectively. The method was used for the determination of several practical samples and Certified Reference Materials. There was no significant difference with the values of this method and reference.Chapter 3: A dispersive liquid-liquid microextraction method combined colorimetric analysis using a desktop digital scanner and digital image analysis was established for determination of total iron in food and water samples using 5-Br-PADAP as complexing reagent. Color analysis is performed by a free software Image J and Gimp on a Pentium4 computer that measures RGB color intensities and grey scale for pixels within the scanner image. Experimental conditions were optimized. Under the optimized conditions, the integral optical density was proportional to iron concentration in 50-800 μg/L with correlation coefficient 0.9852. The limit of dection(LOD) and limit of quantitation(LOQ) were 14 μg/L and 50 μg/L, respectively. Several food and water samples and three kinds of Certified Reference Materials were detected using this method. The method has the potential to be made portable for remote test by operating portable scanner and tablet pc with relatively low cost.Chapter 4: The colorimetric analysis was developed using a smart phone to detect total iron in food and water samples based on reddish orange solutions of Fe2+ and chromogenic agent phenanthroline complex. Smart phone equipped with free android color picker | software Color Grab which read the color characteristic value of the colored solution. The Factors such as the p H value and the concentration of chromogenic agent were optimized. The linear relationship between the color characteristic value and iron concentration with various mathematical model were established. By comparing the linear range, sensitivity, LOD and LOQ, the best mathematical model was selected to detect the total iron in the actual samples. The results were also compared with UV-vis spectrophotometric method and no significant difference were found.