The Application Of Catalytic Potentiometric Titration In Microelement Analysis

With the incessant development of society and science, people pay more and more attention to the study of life , and the effect of the ingestion of the environment and food on the body health. Today's biology and medicine have proved enough that microelement have close relations with body's health. Essential microelement is the indispensable nutrition for human body, and it plays an very important role in life. But the excess ingestion can cause disease. The poisonous microelement can produce extreme harm to the health. If the content exceeds the permissive rang of the body, it can destroy the immune and nervous system of human body, and induce the production of many diseases. Therefore, environmental inspection and food analysis attract more and more attention, the microelement inspection appears especially important. Catalytic titration is an analytical method which determines the titrimetric endpoint based on the catalytic reaction. The titrimetric method has not only high sensitivity of the kinetic method based on catalytic reactions but also has good accuracy of the classical titrimetric analysis. This technique is simple and doesn't need expensive instrument. So it is suitable for common-amount analysis as well as the micro-amount analysis and the determination for microelement in environment and food. Catalytic titration is very convenient, accurate, precise and quick, so it has broad prospect especially in China and some other developing countries. This paper make an overview on the development of the microelement determination by catalytic titration, and establish a new method based on catalytic potential titration. This method were applied to the determination of food and environment samples.1. Catalytic TitritionCatalytic Titrition is an analytical method which indicates titrimetric end-pointbased on the catalytic reaction, so this method not only have the high sensitivity of the kinetic method and high accuracy of the classical titrimetric anlysis, but also is sample and quick without any expensive instruments. The main principle of catalytic end-point indication can be described as follows: The proper indicator reaction was added to the inhibitor solution which is to be determined. Before the end-point of the titration, the drippy catalyst are consumed by inhibitor, so the rate of indicator reaction is very slow, the concentration of the catalyst almost haven't changes, accordingly the electrode potential varies slowly. When the end-point arrives, a excess drop of catalyst can catalyze the indicator reaction instantly, so the concentration of indicator can change greatly, its physical and chemical properties also vary at the same time. Thereby the end-point of titration can be indicated. There are many kinds of titration techniques in catalytic titrimetric analysis, such as direct titration, back titration, reversed titration, displacement titration etc. There also have some methods for the end-point detection in catalytic titration: visual and photometric observation of the indicator reaction, potentiometric observation of the indicator reaction and thermometric observation of the indicator reaction. Catalytic titration is popularly applied in determining trace element because of its high sensitivity and high accuracy. This chapter reviews the application of catalytic titration in analyzing trace element and its compound since 1980.2. The application of catalytic potentiometric titration in determination of environment sample(1) Determination of trace lead(II) in the waste water of storage battery by Catalytic potentiometric titration using methyl violet ion selective electrodeLead is one of the heavy metals which can bring great harms to environment. It can cause cumulative poisoning in body, induce to anaemia and distal neuritis, and prohibit the growth of intelligence for children. Therefore determination of lead is always animportant index of environmental inspection. A new potentiometric titration with catalytic end point indication for the determination of t...