Study On Capillary Micro-Cell/Gelatin Membrane-Laser Thermal Lens Spectrometry And Its Application

Laser thermal lens spectrometry （TLS） is a kind of spectrum analysis method which based on the thermal lens effect. It is widely applied in various fields because of the high sensitivity, low detection limit and high spatial resolution. In this paper, by using capillary as a sample micro-cell, TLS was applied to determination of phosphorus, malachite green, and lead; By using the gelatin film as the reaction field, TLS was applied to the determination of cysteine. This study has important value for low volume samples analysis. The thesis includes the following five parts.Chapter 1:ReviewThe developments of the TLS, theoretical basis, instrument device as well as the application in the chemical analysis were briefly introduced. From the perspective of low volume samples analysis, the topic and research content of the thesis was proposed.Chapter 2:Molybdenum blue method combined with laser thermal lens spectrometry for determination of phosphorus by capillary micro-cellBy using a glass capillary as the determined micro-cell, a laser thermal lens spectrometry for determination of micro sample was proposed in this paper. Theory expression of laser thermal lens spectrometry was given. The effect of light reflection of the capillary micro-cell, its position in the optical path of laser thermal lens spectrometry and enhancement effect of organic solvent were discussed. The method has been applied for determination phosphorus in soil and water samples. The results show that the laser thermal lens spectrometry with a capillary micro-cell is an excellent determination method for the micro sample analysis and can be widely applied to determination of other micro-analytes.Chapter 3:Laser thermal lens spectrometry determination of malachite green after cloud point extraction by using capillary as the sample micro-cellA novel method of Capillary micro-cell-cloud point extraction-laser thermal lens spectrometry was developed. By using two kinds of surfactants, after the process of cloud point extraction, a glass capillary pipette directly organic phase without further dilution. In addition, thermal lens organic solvent enhancement effect can improve sensitivity. Thermal lens spectrometry operation easily and has high sensitivity, it applied to the determination of malachite in fishpond water samples with satisfactory results.Chapter 4:Solidified floating organic drop micro-extraction combined with laser thermal lens spectrometry for determination of leadA new method of solidified floating organic drop micro-extraction （SFODME） combined with laser thermal lens spectrometry （TLS） was developed for the determination of lead in environmental water samples with dithizone as chelating reagent in SFODME. Lead react with dithizone to form a red complex which was extracted into 1-undecanol whose melting point close to room temperature, so that the products can be pro-concentrated and separated. By using a capillary as the micro-cell, the signal of lead can be directly measured without further dilution by organic solvent. The developed method required less organic solvent and operated easily. It applied to the analysis of lead in cosmetics with satisfactory results.Chapter 5:Determination of cysteine on the gelatinous gel membrane by thermal lens spectrometry based on the cysteine competing for Zn （Ⅱ） with ZinconA novel method for determination of cysteine was proposed by thermal lens spectrometry based on the cysteine competing for Zn（Ⅱ） with Zincon. The complex of Zincon-Zn（Ⅱ） was used as the indicator which was immobilized on a gelatinous gel membrane. Under optimum conditions, the cysteine was determined on the gelatinous gel membrane. Gel membrane can be used repeatedly. With CCl₄ as the measured medium, the proposed method has good selectivity and reproducibility which successfully applied to the determination of cysteine in human urine sample.