| This thesis is divided into two parts.(1) The use of rhodamine B(Rh B) and rhodamine 6G(Rh6G) for food coloring has raised serious concerns because of the carcinogenicity,reproductive and developmental toxicity towards humans and animals, thus,have been banned in food stuff by many countries. Therefore, sensitive and reliable methods for the determination of Rh B and Rh6 G in food samples are highly demanded. In this study, two novel methods, first derivative spectrophotometric method(1D) and first derivative ratio spectrophotometric method(1DR), have been developed for the simultaneous trace determination of Rh B and Rh6 G in food samples after dispersive liquid-liquid microextraction(DLLME). The combination of derivative spectrophotometric techniques and DLLME procedure endows the presented methods with enhanced sensitivity and selectivity. Under the optimum conditions, the linear calibration curves ranged from 5 to 450 ng m L-1for both Rh B and Rh6 G by1D and1 DR method. The correlation coefficients(r)were 0.9997 for Rh B and 0.9977 for Rh6 G by1D method, and 0.9987 forRh B and 0.9958 for Rh6 G by1DR method, respectively. The recoveries ranged from 88.1% to 111.6%(with relative standard deviation(RSD) less than 4.4%) and 91.5% to 110.5%(with RSD less than 4.7%) for1 D and1DR method, respectively. The calculated limits of detection(LODs) based on the variability of the blank solutions(S/N=3 criterion) for 11 measurements were in the range of 0.48 ~ 1.93 ng m L-1for both methods. The influence of interfering substances such as foreign ions and food colorants which might be present in the food samples on the signals of Rh B and Rh6 G was examined. The developed methods have been successfully applied to the determination of Rh B and Rh6 G in black tea, red wine and chilli powder samples with the characteristics of simplicity, cost-effectiveness,environmental friendliness, and could be valuable for routine analysis.(2) Metronidazole(MNZ) is widely used for treating diseases caused by protozoa or anaerobic bacteria in human being. It has also been used to promote the growth of cattle, pigs and poultry, and to improve feed efficiency in breeding industry. However, when the metronidazole cumulative dose exceeds a certain value, it will cause harm to the toxic effects of humans and wildlife health. Therefore, the researches on new methods to determine MNZ are of great significance for health maintenance.In view of the disadvantages of the present methods, in this study, advanced electrochemical sensors based on heterogeneous double-layered-based molecularly imrinted polymer was constructed and new electroanalysismethods was developed, respectively, for detecting MNZ in urine, plasma and pharmaceutical formulations. The as-developed duplex molecularly imprinted film, which was used as recognition element of the sensor,combined the advantages of conducting molecularly imprinted polymer and molecularly imprinted polysiloxane. This film not only made feasible the direct and efficient signal transformation between the target analytes and the transducer, but also enhanced the imprinting recognition capability with extensive applicability. The recognition and detection principles were revealed for the new developed sensors by lucubrating the sensing mechanism and the inherent correlations between the sensors’ performances and the factors which include the composition of the duplex molecularly imprinted film, the parameters selected for the electroanalysis, and so on.This study will open up a new platform for the sensor research based on molecularly imprinted polymers, provide new technologies for food inspection, and is an original research with important academic value and application prospect. |
PDF Full Text Request