Differential Kinetic Spectrophotometric Determination Of Some Substances In Organic Compound System With The Aids Of Chemometrics

The research mainly aims at a growing concern for the food, drug and environmental aspects of the complex multi-component system for rapid quantitative determination. Meanwhile, an overview of the application of chemometric approaches to differential kinetic analysis in recent years was studied. The chemometrics methods were used for the analysis of the spectra and the kinetic data, which obtained from the experimental, then discussed the principles of kinetic method and its practical application, and explored the feasibility of using chemometrics in the complex system to achieve simultaneous determination of multi-component material.This thesis is composed of five chapters.Chapter 1In chapter one, it was reviewed the application of chemometric approaches to kinetic analysis for the aspects of food, drug and environmental. Multivariate linear regression approaches, derivative technique, factor analysis, multivariate calibration approaches based on factor analysis, kalman filter approach and artificial neural networks approaches are summarized and discussed in this section. In addition, the prospects of chemometrics in kinetic analysis were also given.Chapter 2A simple and sensitive kinetic spectrophotometric method was proposed for simultaneous determination of cephalexin and trimethoprim in pharmaceutics samples and human urine. Cephalexin and trimethoprim were oxidized resulting in a colorless product by yellow ammonium cerous sulfate in appropriate acidic medium. Under the optimized experimental conditions, the chemometrics multivariate calibration methods, such as partial least squares (PLS), principal components regression (PCR) and radial basis function-artificial neural network (RBF-ANN) were applied to the resolution of the kinetic curves to determine these two compounds. The linear ranges are 0.5-8.0mg L^-1 and 0.25-4.0mg L^-1 for cephalexin and trimethoprim, respectively. The limits of detections are 0.16mg L^-1 and 0.12mg L^-1 for these two compounds, respectively. This method was successfully applied to the analysis of pharmaceutical samples and human urine with satisfied results, which compared well with those obtained by HPLC method, as well as the claimed values.Chapter 3A fast and accurate procedure has been developed for the simultaneous determination of sulfanilamide artificial sweeteners (acesulfame-k, sodium cyclamate and sodium saccharin) in foodstuff samples has been developed. The method was based on the reduction of violet potassium permanganate by sweeteners in the alkaline medium at 70℃to form green potassium manganate peaked at 608nm. Furthermore, linear calibration graphs for each sweetener were obtained in the concentration ranges of 0.2-4.8, 0.5-10.0 and 0.8-5.6mg L^-1 for acesulfame-k, sodium cyclamate and sodium saccharin, respectively. Since the kinetic rates of acesulfame-k, sodium cyclamate and sodium saccharin are similar and their kinetic data are seriously overlapped, chemometrics methods, such as partial least squares (PLS), principal component regression (PCR) and classical least squares (CLS), were applied to resolute the overlapped kinetic data. The proposed method was also applied for the determination of these three sweeteners in foodstuff samples, and the results were well comparable with the ones of HPLC method. Chapter 4A procedure for the simultaneous kinetic spectrophotometric determination of aminocarb and carbaryl in vegetable and water samples was described. The method was based on the difference in the rate of their oxidation with potassium ferricyanide (K₃Fe(CN)₆) as the oxidant in appropriate alkaline medium. Both species instantly oxidize, giving rise to compounds which present maximum values of absorbance close to 420nm. Under the optimized experimental conditions, the linear ranges are 0.05-0.6mg L^-1 and 0.1-1.2mg L^-1 for aminocarb and carbaryl, respectively, and the kinetic data collected were processed by chemometrics methods, such as classical least squares (CLS), partial least squares (PLS), principal components regression (PCR), back propagation-artificial neural network (BP-ANN), radial basis function-artificial neural network (RBF-ANN) and principle component-radial basis function-artificial neural network (PC-RBF-ANN), which were applied to the resolution of the kinetic curves to determine these two carbamate pesticides. The results showed that the PLS and PC-RBF-ANN calibration models gave the lower prediction errors than other chemometrics methods. The proposed method was successfully applied to simultaneous determination of aminocarb and carbaryl in vegetable and water samples, and satisfactory results were obtained.Chapter 5In the last part, a sensitive, highly selective kinetic method for the simultaneous quantitative determination of three dithiocarbamate fungicides (thiram, ziram and ferbam) was researched and developed. The method was established on the different kinetic behaviours of the analytes that react with phenylfluorone in the presence of cetyltrimethyl ammonium bromide (CTMAB) as a surfactant. The kinetic data were collected from 200 to 700nm within a time range of 0-240s at 2s intervals, and the reaction data were recorded at the analytical wavelength (523nm). Different variables affecting the system under study were carefully evaluated. Under the optimum conditions, the analytical curves give a linear range of 0.25-4.5, 0.1-2.0 and 0.05-0.1mg L^-1 for thiram, ziram and ferbam, respectively. Since the kinetic behaviours of thiram, ziram and ferbam overlapped seriously, and to avoid tedious separation procedure and improved the accuracy and precision of determination for three dithiocarbamate fungicides, the data obtained were processed by chemometrics methods, such as classical least square (CLS), partial least squares (PLS1 and PLS2), principal component regression (PCR), radial basis function-artificial neural network (RBF-ANN) and principle component-radial basis function-artificial neural network (PC-RBF-ANN), using the normal and the first-derivative kinetic data. The results show that calibrations based on first-derivative data have advantages for the prediction of the analytes, and the PLS1 and PC-RBF-ANN gave the lower prediction errors than other chemometrics methods. Following the validation of the proposed method, it was applied for the determination of the three-dithiocarbamate fungicides in several real samples; and the standard addition method yielded satisfactory recoveries.