Determination Of Toxic Nitrogen Compounds By Capillary Electrophoresis

Capillary electrophoresis (CE) has been successfully applied to the analysis of the complex matrices in biology, chemistry, medicine and environment because of its advantages of excellent separation efficiency, rapid analysis, convenient and minimal use of the samples and solvents. Capillary zone electrophoresis (CZE) is an important separation mode of CE. In my dissertation, I focused on its application to the separation and determination of some compounds containning nitrogen atom in their chemical structures. After separation conditions were systematically studied such as pH, concentration, and types of backgound solution, applied voltage, the optimum electrophoretical conditions were obtained. The developed method was then verification by the real samples with satisfactory results. This paper consists of three chapters:In chapter 1:This chapter introduced some methods for the analysis of some compounds containing nitrogen atom in their chemical structures. These analysis methods are mainly chromatography, and some of them have been widely used as national standards. The advantages of capillary electrophoresis as an alternative method were summarizeda in this section, and its typical application to some compounds containing nitrogen atom in their chemical structures was presented.In chapter 2:A nonaqueous CE method was developed for the quantitative determination of acrylamide in traditional Chinese medicine. Acrylamide acquires a proton in a low-pH environment in ACN, and thereby migrates under its own electrophoretic mobility in CE. Thus, nonaqueous separation of acrylamide was achieved by employing 30 mmol/L HClO4 in ACN as the running electrolyte, working at 20 kV in un-coated fused silica capillaries. Direct detection was carried out at 198 nm. The run-to-run and day-to-day precisions for the corrected peak areas were calculated as 0.4-1.7 and 1.1-2.4%, respectively. The method is simple, rapid, inexpensive, and applicable for the determination of acrylamide in Chinese medicine.In chapter 3:Nitrite, nitrate and thiocyanate have been quantified in non-smoker and smoker saliva by capillary zone electrophoresis (CZE), using a 20 mmol/L phosphate buffer at pH 6.0 (ionic strength was adjusted to 0.0816 mol/kg with Na2SO4) as a running buffer. The proteins and enzymes in saliva sample were removed by centrifugation and filtration of the mixture of acetonitrile and saliva sample. Bromate was selected as the internal standard because it was impossibly present in original saliva and it did not interfered with the selected three anions. Linearity of the ratio of peak areas for analyte and internal standard against analyte concentration was observed from 0.01 to 1.00 mmol/L with a linear coefficient of 0.999 for nitrite, from 0.10 to 6.00 mmol/L with a linear coefficient of 0.999 for nitrate and from 0.05 to 2.00 mmol/L with a linear coefficient of 0.999 for thiocyanate. The whole separation was achieved in less than 10 min. The simpler sample pretreatment and relatively low running cost make CZE good alternative to existing methods.