Differential Kinetic Spectrophotometric Determination Of Some Organic Substances In Complex Systems

Differential Kinetic spectrophotometry is a simple and fast method for the simultaneous determination of multi-component system. With the aid of chemometrics, the multi-component regression are proposed for the analysis of kinetic and spectra data. In this paper, the main target of the research is to find different kinds of differential kinetic spectrophotometry for the simultaneous determination of some organic substances in some complex systems, environment, food and pharmaceuticals amples, with the aids of chemometrics. Meanwhile, experimental conditions were optimized, the mechanisms of reaction were investigated and discussed, the optimum chemometric model was obtained and applied for the determination of real samples. The results obtained by the proposed kinetic mehtods were compared with the one of HPLC method, no significant differences between them can be found.This thesis is composed of five chapters.In chapter one:It was reviewed the development of kinetic method with the chemometrics for multicomponent analysis in the environment, food and pharmaceuticals systems. And some common kinetic reaction mechanisms were studied. Besides, the prospects and relative merits of chemometrics in kinetic simultaneous analysis were also given.In chapter two:A novel kinetic spectrophotometic method was developed for determination of pyrocatechol, resorcin, hydroquinone and phenol based on their inhibitory effect on the oxidation of Rhodamine B (RhB) in acid medium at pH=3.0. A linear relationship was observed between the inhibitory effect and the concentration of the compounds. The absorbance associated with the kinetic reactions was monitored at the maximum wavelength of557nm. The effects of different parameters such as pH, concentration of RhB and KBrO3, and temperature of the reaction were investigated and optimum conditions were established. The linear ranges were0.22-3.30,0.108-0.828,0.36-3.96and1.52-19.76μg mL-1for pyrocatechol, resorcin, hydroquinone and phenol, respectively, and their corresponding detection limits were0.15,0.044,0.16and0.60μg mL-1. The measured data obtained were processed by several chemometics methods, such as principal component regression(PCR), partial least squares(PLS) and artificial neural network(ANN), and a set of synthetic mixtures of these compounds was used to verify the established models. It was found that the prediction ability of PLS, PCR and RBF-ANN was similar; however, the RBF-ANN model did perform somewhat better than the other methods. The proposed method was also applied satisfactorily for the simultaneous determination of pyrocatechol, resorcin, hydroquinone and phenol in real water samples.In chapter three:A sensitive kinetic-spectrophotometic method for the simultaneous determination of antibiotics in a mixture, specifically of amikacin (AMK), gentanicin (GTM) and etimicin (ETM), has been researched and developed with the use reaction kinetics.1,2-naphtoquinone-4-sulphonate (NQS) was used as the derivative reagent to produce colored products in medium of pH9.02, and their spectra were collected in order to monitor the kinetics of the reaction (at475nm). Calibration models for quantitative analysis of these mixtures were developed with the use of the principal component regression (PCR), partial least squares (PLS) and radial basis function-neural networks (RBF-ANN) methods. Verification of these models with the use of a separate set of synthetic samples was successful with the RBF-ANN calibration performing best. This method was then applied for the prediction of the antibiotics in real samples-spiked injection solutions, water and serum samples, and the results were successfully verified with the use of an HPLC method. Therefore, this method is a convenient alternative to the commonly used HPLC approach for the determination of these three antibiotics in variety of samples; it also has relatively high selectivity and low-costs.In chapter four:With the aid of chemometrics, a simple kinetic method was developed for the simultaneous determination of three methyl derivatives of methyl xanthine, caffeine, theobromine and theophylline, in food samples. This method is based on the different kinetic characteristics of the reactions of caffeine, theobromine and theophylline, with a common oxidizing agent cerium (IV) in the presence of sulfuric acid, and monitor the change of the absorbance at the maximum wavelength of320nm. Experimental conditions such as the concentrations of the reagents, sulfuric acid and cerium (Ⅳ) were optimized. Appropriate linear ranges (0.4-8.4μg mL-1) for all three analytes were obtained, and the limits of detection were0.30μg mL-1for caffeine,0.33μg mL-1for theobromine and0.1μig mL-1for theophylline. The absorbance data collected from a set of laboratory prepared mixtures of analytes were processed by two chemometrics approaches, partial least squares (PLS) and artificial neural network (RBF-ANN), and the established models were then used for prediction of an unknown set of mixtures. It was found that the RBF-ANN method afford better precision relatively than PLS. The proposed method was also applied satisfactorily to the determination of caffeine, theobromine and theophylline in real samples, and there were no significant differences as compared with the HPLC method as a reference.In chapter five:A highly sensitive, selection and simple kinetic method has been developed for the determination of two kinds of glucocorticoids resideus, such as prednisone and dexamethasone. The method was based on the reduction of violet potassium permanganate by glucocorticoids in the alkaline medium at35(C to form green potassium manganate peaked at610nm. Furthermore, linear calibration graphs for each glucocorticoid were obtained in the concentration ranges of0.8-8.0μg mL-1and0.02-0.20μg mL-1for prednisone and dexamethasone, respectively. The detection limits of the proposed method were0.43and0.01μg mL-1. The high sensitivity and selectivity of the proposed method allowed its successful application to real samples, and the results were well comparable with those of HPLC method.