Studies On Near Field Thermal Lens Spectrometry And Its Application

Thermal lens spectrometry is a new spectrometric technique based on thermal lens effect. It has attracted much attention for the advantages of extremely high sensitivity, low detect limit and suitability for micro-sample analysis, and has been proved to be a powerful tool for trace analysis. This dissertation focuses on the near field thermal lens spectrometry and its application. It consists of the following four parts.Part I: ReviewChapter 1 : Advances in thermal lens spectrometryThis review considers the new development of thermal lens spectrometry after 1 990. Instrumental developments, theoretical treatments and practical applications are considered in terms of their analytical use and potential. Seventy eight references are cited.Part II: BackgroundThe conventional instrument of laser thermal lens spectrometry is difficult to be microminiaturized and commercialized for the long distance between the sample and the detector, which limits the application of the method. Therefore, development of near field thermal lens spectrometer that is simple in structure and easy to be adjusted is of significance for the practical use of the method.Part III: Theory and InstrumentChapter 2: Theory and instrument of near field thermal lens spectrometryThe theoretical model of near field thermal lens spectrometry has been established.Its quantitative relationship has been given:An instrument of near field thermal lens spectrometry has been developed. The distance between the sample cell and the detector has been shortened from about 2 m to 25 cm. The parameters of the instrument have been determined and its performance has been tested. The theoretical and experimental studies have showed that the near field thermal lens spectrometry can get the same sensitivity as conventional thermal lens spectrometry. This instrument, which is compact and simple in structure, has been applied to the determination of nile blue A with good linearity for the concentration range of 1.08xlO~8~ 2.0xl(T7 rnol-L"1 nile blue alcohol-water solution.Part IV: ApplicationsChapter 3: Determination of kinetic parameter of catalytic reaction by near field thermal lens spectrometryA new method for the determination of kinetic parameter of catalytic reaction by laser thermal lens spectrometry is proposed. The kinetic parameters of the kinetic reaction, in which indium catalyzed oxidation of nile blue A by potassium periodate to form pink product in weak acidic medium, is determined successfully by near field laser thermal lens spectrometry. The catalytic reaction is first-order in Ir(IV), nile blue A and KIO4. The apparent activation energy of the catalytic reaction is found to be 70.9 kJ/mol. The rate equation of the reaction has been established. The reaction mechanism is proposed. A super sensitive method for the determination of trace iridium based on the catalytic reaction is established. The linear relationship between lg(So/Sc) and the concentration of iridium is obtained in the range of 0.05~2.4 ng/mL. The detection limit is 6.2xlO"12 g/mL. The method has been applied to the determination of trace iridium in ore. The results analyzed by the method are in good agreement with the standard value.Chapter 4: Determination of utratrace silver using surfactant as sensitize by catalytic by near field thermal lens spectrometryA new method for the determination of utratrace silver(I) by near field thermal lens spectrometry has been developed. This method is based on the silver(I) catalyzed discoloring reaction of bromoceresol green oxidized by sodium persulphate in the presence of a , a '-bipy as activator and TritonX-100 as sensitizer. The reactionmechanism was discussed. A S presents a linear relationship with the concentration of silver in the range of 0~30 ng-ml"1. The detection limit is 2xlO~2 ng-ml"1. The method has been used for the determination of silver in lead powder and photographical paper with satisfactory results.Chapter 5: Determination of trace iodine based on catalytic kinetic react...