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Microwave-assisted synthesis for open tube capillary electrochromatography column preparation and application performance

Author: EHongJun
Tutor: YangYi
School: Beijing University of Chemical Technology
Course: Applied Chemistry
Keywords: Microwave-assisted synthesis Polyamidoamine dendrimers Open tubular capillary electrochromatography Fluorescence labeling technique Enzyme capillary microreactor
CLC: O657.7
Type: PhD thesis
Year: 2009
Downloads: 148
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Abstract


Open tubular capillary electrochromatography(OTCEC) is one of the most important approaches in capillary electrochromatography(CEC). Microwave irradiation method has become increasingly popular for modern chemical synthesis strategies sine.it’s first application towards organic chemistry.Compared with conventional synthesis process, microwave irradiation method has the advantages such as,heating system with uniform temperature,selective heating and no hysteresis effect. Polyamidoamine(PAMAM) dendrimers stationary phase for OTCEC was prepared from silanized fused-silica capillaries by 3-Aminopropylmethyldimethoxysilane(KH 550) with repeating tertiary amine/amide branching units using microwave-assisted method. Fluorescein isothiocyanate(FITC) is one of the most commonly used fluorescent dyes which act as an amine reactive label in bioassay.FITC was used as a label for the characterization of PAMAM dendrimer modified capillary column.The results verified that the preparation of PAMAM dendrimer modified column with microwave irradiation is feasible.Comparing with the conventional synthesis,microwave irradiation significantly improved the reaction speed and shortened the preparation time.The separation of Alanine and Proline was demonstrated with prepared PAMAM/OTCEC column.The results showed that the separation was gradually improved with the increasing of PAMAM generation,and the baseline separation can be obtained by G3 PAMAM dendrimer modified capillary column.The reproducibility of the PAMAM/OTCEC column was evaluated by measuring the RSD of the migration time.The results showed that the reproducibility of the column was satisfactory(RSD<3.0%).The rate of column efficiency decline was used to examine the stability of G3 PAMAM/OTCEC column. Alanine and Proline was used to determine the stability for consecutive 10 days,the results showed that the columns have a good stability.At present,cyclodextrins(CDs) and their derivatives are the most widely applied chiral selector due to its low price,low UV absorbance, and unique structure.In this study,FITC was used as label for the characterization of KH 550 modified capillary column prepared by microwave assisted method.The results verified that the preparation of KH 550 modified column with microwave irradiation is feasible. Bromoacetate-substituted-β-cyclodextrins(Br-β-CD) have been successfully bonded to KH 550 modified column as chiral stationary phase in OTCEC.Comparing with the conventional synthesis,microwave assisted process significantly improved the reaction speed and shortened the preparation time from 16h to 40min.Baseline chiral separation of N-acetyl-DL-methionine and 1-phenyl-1,2-ethanediol was obtained in Br-β-CD modified column.The reproducibility of the Br-β-CD/OTCEC column was evaluated by measuring the RSD of the migration times of chiral compound 1-phenyl-1,2-ethanediol.The migration time data indicated that the reproducibility of the column was satisfactory(RSD<2 %).Separation efficiencies of acetone in the Br-β-CD/OTCEC column decreased 6.77%after 10 days,good stabilization was obtained.An enzyme is a biological catalyst,which has high efficiency under mild conditions and is highly selective.In the concept of utilizing the natural catalysts to manufacture various products,such as foods or pharmaceuticals,immobilizing enzyme technique was born.The ability to easily separate immobilized enzymes from the reaction mixture offers an additional advantage for multiple use of the enzyme,resulting in reduced cost and time to remove the enzyme from the measurement samples.The preparation of the immobilized microenzyme reactors inside capillaries or channels of the microfluidic devices represents another step in the development of the miniaturized systems for rapid analyses of very small sample sizes.The studied enzymes can be covalently attached on the surface of the capillaries or channels.The advantage of the covalent bonding is that the leakage of the immobilized enzyme is minimized. PAMAM dendrimers stationary phase for OTCEC was prepared successfully using microwave-assisted method.Through the high branches of the dendrimers,the capacity of the surface introduction can greatly increase the immobilized enzyme and reduced the enzyme molecules immobilized in the rigid matrix surface,thus reducing the possibility of changes in conformation to maintain the enzyme activity.In this work,the enzyme micro-reactor was prepared in PAMAM dendrimers modified capillary using glutaraldehyde as a cross-linking agent and aminoacylase as immobilized enzyme.The product of enzyme capillary micro-reactor was separated by capillary zone electrophoresis. Peak area of the product represented the enzyme activity. N-acetyl-DL-methioine was passed through a 15cm enzyme capillary micro-reactor.The results showed that the optimal conditions were, substrate concentration 17.5μg mL-1 having a flow rate of 4μL min-1 at 37℃using phosphate buffer of pH 7.5.Under the optimized conditions, the substrate N-acetyl-DL-methionine showed enzymatic degradation for 10 days consecutive(analyzed 5 times a day).The enzyme capillary micro-reactor showed good stability.Layered double hydroxides(LDHs) are layered compounds with anion-exchange ability.The intercalation of sulfatedβ-cyclodextrin into LDHs by the ion-exchange method was used.In this study,the sulfatedβ-cyclodextrin intercalated in layered double hydroxides (Mg2Al/SO3-β-CD/LDH) was chosen as stationary phase for open tubular capillary electrochromatography and was applied to separate the receme of 1-phenyl-1,2-ethanediol under the optimized conditions.

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CLC: > Mathematical sciences and chemical > Chemistry > Analytical Chemistry > Instrument analysis ( physics and physical chemistry ) > Chromatographic analysis
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