Study On Application Of Capillary Electrophoresis-Laser Introduced Fluorescence In The Analysis Of Complex Samples

1. PrefaceIn recent years, capillary electrophoresis (CE) has developed into a highly effective and economic separation analysis technologies. It has the advantages of high separation efficiency, low cost, low consumption of reagents, short analysis time, easy to wash column, and can be used for the analysis of various types of materials. This chapter briefly introduces the principle, characteristics and device of capillary electrophoresis and the detection technologies combined with CE as well as liquid phase micro extraction technology principle and its applications. This paper was based on the mechanism of the fluorescence derivatization, nonfluorescent active analytes were convert to highly fluorescencent active adducts, and combined with hollow fiber membrane liquid phase microextraction, analytes were purified and enriched by this method, and then detected by laser-induced fluorescence detection. This chapter also summarizes the research purpose and significance.2. Study on the fluorescence derivative mechanism of low-molecular-weight carbonyl compounds and CE-LIF analysisFormaldehyde and glyoxal are used as preservatives in cosmetics commonly, however, it is a challenge to direct determination of these aldehydes due to their volatility, high polarity and chemical reactivity, as well as the lack of chromophore or fluorophore. A capillary zone electrophoresis with laser-induced fluorescence detection (CZE-LIF) method has been developed for determination of above aldehyde preservatives based on fluorescein 5-thiosemicarbazide derivatization. Under a capillary zone electrophoresis mode without additional additives, formaldehyde and glyoxal could be well separated from their main aldehyde homologs such as acetaldehyde, propylaldehyde, butyraldehyde, pentanal and methyl-glyoxal by using a small diameter (25 μm i.d.) and longer capillary tube (80 cm of effective length) as the separation channel. The limits of detection were achieved at nanomole-per-litre level, and the RSDs were in the range of 1.4-3.2% for peak area, and 1.6-3.2% for migration time, respectively. Furthermore, the derivative efficiency was greatly improved by magnetic stirring, and the derivative reaction could be finished within 60 min. The presented method has been successfully used for real cosmetic samples, and their recovery data were in range of 92-112%.3. Study of fluorescence derivative mechanism of low-molecular-weight amino compounds and CE-LIF analysisThis paper established a capillary electrophoresis with laser-induced fluorescence detection method combined with hollow-fiber membrane liquid-phase microextraction preconcentration technology, then this method was used to determine the biogenic amines and their precursor amino acids (cadaverine, putrescine, spermidine, ornithine, lysine, arginine) in saliva samples. A comprehensive study has been performed on the effect of various experimental conditions in this paper. Under the optimal conditions, six kinds of analytes achieved the baseline separation within 30 min. the conclusion can achieve a good level of linearity (r2>0.998) at three orders of magnitude range, the detection limit is between 0.0072 and 0.26 mmol/L, the enrichment factors of the analytes can reach 19 to 218 times. Therefore, the method can be used successfully to detect related oral disease in healthy people and patients with different oral diseases, and can provide a potential detection method for noninvasive diagnosis of oral diseases.