Determination Of Trace Amounts Of Manganese By Flow Injection Catalytic Spectrophotometry

Trace levels of Mn is determined using flow-injection catalytic kinetic spectrophotometry. Due to the catalytic effects of Mn(II), strongly enhanced by nitrilotriacetic acid, sodium periodate could oxidize tetrabase [4,4'-bis(dimethylamino)-diphenylmethane] rapidly at room temperature in an acetate buffer medium (pH=5.4). Flow injection technique is used to control the merging and reaction timing of the reagents and samples. The measurements are conducted at 602 nm the unstable blue intermediate product of the reaction, which greatly improves the sample throughput. A detection limit (3 o ) of 0.073 ug/L is achieved at a sampling frequency of 60/h.The relative standard deviation is 0.5% for the determination of 10 ug/L Mn (n=l 1).The thesis is divided into four chapters.In the first chapter, a review is provided on the basic theories and advantages of flow injection analysis technique, and the basic principles of catalytic kinetic spectrophotometry and its main characteristics with the emphasis on the applications of manganese analysis by catalytic kinetic spectrophotometry.Chapter 2 introduces the apparatus, the reagents and the methods used in the present study.In the Results and Discussion, practical considerations on flow injection systems for the catalytic kinetic analysis of trace amounts of manganese are discussed, leading to the optimized flow injection manifold used in the present study. The possible mechanism of the kinetic reaction is given and discussed. The physical and chemical parameters are optimized and the potential effects of interferences on determination of manganese are examined. The optimized system is validated by the analysis of an estuarine water reference material, SLEW-2 (National Research Council of Canada) and applied to the analyses of several natural waters with satisfactory recoveries.Chapter 4 summarizes the characteristics of the proposed system.