Studies On Determination Of Harmful Ingredients In Foodstuffs Using Flow Injection Analysis

In this dissertation, methods for the determination of the harmful ingredients including formaldehyde, sulfite and boron in food samples are developed using flow injection spectrophotometry. The methods are simple, sensitive, rapid and automatic.The disseration is divided into four parts.In chapter 1, the flow injection analysis (FIA) technique is reviewed with the emphasis on its application of food analysis using spectrophotometry.In chapter 2, a simple method for the determination of formaldehyde in foodstuffs is described. Flow injection technique is used to control the merging and reaction timing of the reagents and sample. Formaldehyde reacts with phloroglucinol in an alkaline medium producing an unstable orange product withλ_max at 474 nm. The calibration graph is linear in a range of 0-10μg/mL formaldehyde. A detection limit of 0.023μg/mL is achieved at a sampling frequency of 35/h. The relative standard deviation is 0.29 % for the determination of 7μg/mL formaldehyde (n=11). The method is simple, quick, sensitive and selective. The proposed method has been successfully applied to the determination of formaldehyde in beancurd stick, preserved jerryfish, dry mushroom and vermicelli samples and the results are in agreement with those obtained by a national standard methods (the AHMT method).In chapte 3, a new method for determination of sulfite in foodstuffs by flow injection analysis is described, which is based on the discoloration of basic fuchsine in an alkaline medium. Operational conditions are optimized with the aim to achieve higher sensitivity. The calibration graph is linear in range of 0.04-1.5μg/mL SO₃^2-at 542 nm. A detection limit of 0.016μg/mL is achieved at a sampling frequency of 38/h.The relative standard deviation is 0.41 % for the determination of 1.2μg/mL SO₃^2- (n=11).This method is simple, fast, sensitive and accurate. The proposed method has been applied to the analyses of several foodstuffs, including beer, white sugar, dried day lily, licorice almond, and vermicelli with satisfactory results. In chapter 4, a new method for determination of boron in foodstuffs by flow injection analysis is developed, which is based on the coloration of boron and 3-meth oxy -azom-ethine-H in an acid medium withλ_max at 420 nm. Operational conditions are optimized and potential interferents are studied. The calibration graph is linear in range of 0.033-7μg/mL B (III) with the present method. A detection limit of 0.033μg/mL is achieved at a sampling frequency of 28/h. The relative standard deviation is 0.36 % for the determination of 3μg/mL B (III) (n=11). The proposed method has been applied to the analyses of several foodstuffs with satisfactory results.