| Capillary electrophoresis (CE), also called as High Performance Capillary Electrophoresis (HPCE), is a kind of liquid phase separation technology. With a high-voltage power supply providing electric field and. a-capillary tube as the separation channel, CE separates the analytes by their different migration rate. It has the characteristics of high efficiency, high speed, ultra-small sample volume, minimal consumption of solvent and ease of clearing up the contaminants. As a result, although rose in the1980s, it has been one of the most fast-developing separation technology in analytical chemistry. Nowadays, CE has been successfully applied in many fields, such as analytical chemistry, food chemistry, medicinal chemistry, biological chemistry and so on. The present thesis described the studies of CE, combined with amperimertric detection (AD) or laser induced fluoscence detection (LIF). CE-AD has been used in the determination of aldehydes in food and disease biomarkers in urine samples, while CE-LIF has been applied in the diagnosis of phenylketonuria. The major contents are described as follows:1. PrefaceThe introduction section retrieved the history of CE development, and introduced the characteristics, the basic theories, the separation modes and the instrumental system briefly. According to the research area of this thesis, the application of CE in food analysis and disease biomarkers has been reviewed. The goal and significance of this thesis dissertation are also introduced.2. A novel capillary electrophoretic method for determining aliphatic aldehydes in food samples using2-thiobarbituric acid derivatizationBased on.derivatization and CE-AD, a novel electrophoretic method for sensitive determination of nine aldehydes in food samples has been developed, including formaldehyde (C1), acetaldehyde (C2), propanal (C3), butanal (C4), pentanal (C5), hexanal (C6), glutaradehyde (Gla),2,3-butanedione (Bud) and methylgloxal (MGo). Experimental conditions of derivatization and CE-AD detection were optimized in detail. Under the optimum conditions, highly linear response(r2≥0.9901) was obtained for aliphatic aldehydes in the concentration range from0.083to15.0mg/L with the improved detection limits (S/N=3) varied from0.008to0.074mg/L. The developed method was validated by detecting the experimental precision, reproducibility and recovery, and the results showed that the analysis was efficient and reliable. The proposed CE-AD method provides a reliable and sensitive quantitative evaluation for non-electroactive and low-molecular-mass aliphatic aldehydes in real sample matrices.3. Determination of DNA damage markers:8-hydroxy-2'-deoxyguanosine and8-nitroguanine by capillary electrophoresis in urineExtensive reports have demonstrated that8-hydroxy-2'-deoxyguanosine (8-OHdG) and8-nitroguanine (8-NO2Gua) can be used as sensitive biomarkers of oxidative DNA damage, as well as potential indicators for a wide variety of cancers. However, due to the low level of the analytes and the complex matrix in urine, the measurement of these two compounds was a challenging work. In this part, a sensitive and low-cost analytical method has been developed for the determination of8-OHdG and8-NO2Gua based on CE-AD after solid phase extraction (SPE). Method developing involved optimization of several parameters, including the working electrode, the acidity and concentration of running buffer, the acidity and concentration of running buffer and the injection time. Under the optimized conditions, the correlation of these two markers was excellent over the concentration range of0.1-50μg/mL, and LODs (S/N=3) were0.02μg/mL for8-OHdG and0.06μg/mL for8-NO2Gua. The average recovery was within the range of100.0%-115.2%. The proposed method was applied to measuring8-OHdG and8-NO2Gua in urinary samples from healthy volunteers and cancer patients. The results showed that the levels of8-OHdG in cancer patients were significantly higher than those in healthy, ones (38.00±21.10μig/L vs.16.51±5.60μg/L), as well as8-NO2Gua (239.17±124.35μg/Lvs.154.38±59.77μg/L). 4. Measurements of amino acids by capillary electrophoresis with laser induced fluorescenceA method of capillary electrophoresis apparatus with laser induced fluorescence detection (CE-LIF) has been developed to identify and quantify seven amino acids, which are markers of some diseases. Amino acids were derivatized with fluorescein isothiocyanate (FITC) prior to CE-LIF analysis. The assay was developed by varying several parameters, and the optimized running buffer system contained80mmol/L borate (pH8.70) and130mmol/L18-crown-6. Under optimum conditions, highly linear response was achieved within concentration ranges of over three orders of magnitudes for those analytes (rL>0.9970). The LODs for different amino acids ranged from0.01-5.0nmol/L while the recovery of standard addition were90.85-104.26%with precision of0.2-1.9%RSD. The proposed CE-LIF method has been successfully applied to the determination of amino acids in biological samples from new-born. This work defines a sensitive and repeatable quantitative evaluation for the fast diagnose of some metabolic diseases of new-born without pain. |
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