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31.
Lämmerhofer M 《Journal of chromatography. A》2005,1068(1):31-57
A review on the advantages, peculiarities, and the potential of enantioselective capillary electrochromatography (CEC) in nonaqueous media is presented. Some fundamentals on CEC with particular focus on enantioselective CEC are discussed. The strategies, concepts, preferentially utilized chiral selectors and column technologies that have been utilized to succeed in highly efficient enantiomer separations by nonaqueous CEC are described thoroughly. 相似文献
32.
Summary A new, rapid, and precise liquid chromatographic method has been developed for simultaneous identification and quantification
of amphetamine,N-methyl-3,4-methylenedioxymetamphetamine,N-ethyl-3,4-methylenedioxymetamphetamine, andN-methyl-1-(3,4-methyl-enedioxyphenyl)-2-butanamine in the presence of other constituents. The compounds were separated on
a monolithic column with a gradient prepared from acetonitrile and 20mm monobasic potassium buffer at a flow rate of 1.5 mL min−1. Quantitation was performed with metoclopramide as internal standard. Use of different flow rates was investigated and enabled
reduction of the separation time from 11 to 3.5 min for seven substances. The method was then applied to ten seized tablets
to identify and quantify their active ingredients. 相似文献
33.
34.
以表没食子儿茶素没食子酸酯(Epigallocatechin-gallate,EGCG)为模板分子,α-甲基丙烯酸为功能单体,乙二醇二甲基丙烯酸酯为交联剂,在光冷引发条件下合成EGCG分子印迹聚合物,利用该聚合物制成分子印迹固相萃取柱,用于固相萃取茶叶提取物茶多酚,对萃取柱中的清洗液、洗脱剂、上载量等进行了选择.结果表明,在萃取柱上载样品之后,先用V(甲醇):V(水)=1:9溶液进行清洗,再用V(甲醇):V(乙酸)=9:1混合液进行目标分子的洗脱,可以得到比较纯的目标物质EGCG(色谱峰相对峰面积达92.4%),萃取柱在上载样品并进行清洗、洗脱之后,EGCG的回收率达69.3%.分子印迹柱具有较好的稳定性和耐用性能,使用20次后其选择性识别能力仍未降低,但空白印迹柱却没有这样的选择性识别能力. 相似文献
35.
Capillary electrophoresis with end-column amperometric detection of urinary 8-hydroxy-2'-deoxyguanosine 总被引:1,自引:0,他引:1
Urinary 8-hydroxy-2'-deoxyguanosine (8OHdG) is an excellent marker of oxidative DNA damage. Until now, urinary 8OHdG has been measured by high-performance liquid chromatography with electrochemical detection. A simple and sensitive method for the analysis of urinary 8OHdG by capillary electrophoresis with end-column amperometric detection has been developed in our laboratory. A single-step solid-phase extraction procedure was optimized and used for extracting 8OHdG from human urine. To improve the sensitivity of this method, a new focusing technique based on a dynamic pH junction was used. The limit of detection was 20 nM (signal-to-noise ratio S/N = 3), the linear range was 50 nM-10 microM, and the correlation coefficient was better than 0.999. The relative standard deviation (RSD) was found to be 0.57% for migration time, and 4.79% for peak current. To show the usefulness of the method, the urinary concentration of 8OHdG in nine healthy persons and ten cancer patients was determined. The urinary concentration of 8OHdG in cancer patients was significantly higher than that in healthy persons. 相似文献
36.
A method based on in-tube solid-phase microextraction and capillary zone electrophoresis (CZE) was proposed for simultaneously determining four amphetamines (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, and 3,4-methylenedioxymethamphetamine) in urine. A poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column, which can provide sufficient extraction efficiency, was introduced for the extraction of amphetamines from urine samples. The hydrophobic main chains and acidic pendant groups of the monolithic column make it a superior material for extraction of basic analytes from aqueous matrix. After extraction, the samples were analyzed by CZE. The best separation was achieved using a buffer composed of 0.1 M disodium hydrogen phosphate (adjusted to pH 4.5 with 1 M hydrochloric acid) and 20% methanol v/v, with a temperature and voltage of 25 degrees C and 20 kV, respectively. By applying electrokinetic injection with field-amplified sample stacking, detection limits of 25-34 microg/L were achieved. Excellent method of reproducibility was found over a linear range of 0.1-5 mg/L. Determination of these analytes from abusers' urine sample was also demonstrated. 相似文献
37.
A polyaluminum chloride (PAC) sample was prepared using a slow alkaline titration method. The Bio-Gel P-100 gel column chromatographic
technique was used to separate and characterize the various forms of aluminum present in the prepared PAC solution. The effluents
from a gel column were monitored using online chemical method: Al-Ferron timed complexation spectrophotometry and by 27Al nuclear magnetic resonance (NMR) spectroscopy. Effects of different experimental conditions such as eluent flow rate, ionic
strength and pH on separation of Al13 were investigated. Experimental results indicated that molecule size exclusion was not the only parameter affecting the column
chromatographic separation efficiency of Al13 but molecule charge as well. Reducing the eluent flow rate, increasing the ionic strength and suitable pH resulted in increase
in the separation efficiency. Experimental results clearly indicated that by varying the experimental conditions, it is possible
to produce pure Al13 species using a gel column chromatographic technique. 相似文献
38.
V. Vojinovi? 《Analytica chimica acta》2006,565(2):240-249
A new alternative method for bioprocess monitoring based on bienzymatic analytical microreactors integrated in a flow injection analysis (FIA) system is described. Glucose-, alcohol-, lactate-, galactose- and l-amino acid oxidases (GO, AO, LacO, GalO and LAAO) and horseradish peroxidase (HRP) are immobilized on controlled pore glass (CPG) and used for the development of glucose, ethanol, lactate, galactose and amino acid sensors. The analytical methodology is based on HRP catalysed reaction of hydrogen peroxide produced by oxidases with phenol-4-sulfonic acid and 4-aminoantipyrine. The immobilized enzymes are characterized and used for preparation of the packed bed analytical microreactors. Shelf life and operational stability of the microeactors are determined. GO/HRP, AO/HRP and LAAO/HRP microreactors showed excellent shelf life, they could be stored and reused for more than 6 months with no or very little activity loss, while GalO/HRP and LacO/HRP could be stored for shorter periods of time (10-20 days). Operational stability of GO and LacO microreactors was very good: an equivalent to 16,900 FIA injections of 25 μl to a LacO microreactor resulted in loss of half of its activity, immobilized GO was so stable that it was impossible to evaluate enzyme halflife. Immobilized GalO and LAAO lose their operational activity much faster: approximately 1400 and 8000 FIA injections of the respective substrate solution in a FIA set-up resulted in 50% activity loss. The methods with all the described microreactors were successfully validated using off-line samples from S. cerevisiae, E. coli and mesenchymal stem cell cultures with HPLC as the reference method. 相似文献
39.
选用1-乙烯基-3-乙基咪唑四氟硼酸盐([VElm]BF4,一种离子液体)作为功能单体,以Co2+为介导离子,结合1-丁基-3-甲基咪唑四氟硼酸盐([BMIM]BF4)/二甲基亚砜(DMSO)二元致孔体系制备了绿原酸印迹整体柱。经过对制备参数的考察,确定最佳比例为绿原酸:Co2+:[VElm]BF4:EDMA(乙二醇二甲基丙烯酸酯)(摩尔比)=1:1:5:20,[BMIM]BF4:DMSO=3:1(V/V),最大印迹因子达2.10。通过优化色谱条件,最终在乙腈:20 mmol/L乙酸钠缓冲液(pH 4.2)=70:30(V/V)时实现了绿原酸及其类似物的完全分离。由此可见,以离子液体为功能单体及致孔剂,在金属介导策略下制备的分子印迹聚合物可实现绿原酸的特异性识别及分离。 相似文献
40.
A flow injection (FI)-reduced volume column system was developed for hemoglobin (Hb) typing to be used as an initial screening method for thalassemia. The column was packed with 140 μl diethylaminoethyl (DEAE)-Sephadex A-50 ion exchange beads. Hb can be separated using Tris–HCl buffer solution with pH gradient 8.5–6.5 and then monitored spectrophotometrically at 415 nm. The hemolysate of 40 blood samples from packed red cells were screened for thalassemia by determining the amount of HbA2 and HbE present. The proposed system was able to predict positive test results from those samples with β, E-trait and EE homozygous thalassemia, Hb types that were independently identified following the conventional method at the hospital laboratory. Advantages of the proposed system over the conventional column technique include low amount of reagents and blood sample needed, short analysis time and low cost. Each analysis required only 80 μl of 50 times diluted packed cells, which is equivalent to 1.6 μl undiluted packed cells, and it can be completed in only 35 min. This simple FI-reduced volume column system was demonstrated to be an economic alternative system for Hb typing to initially screen some types of thalassemia such as β-trait, E-trait and EE-homozygous which are commonly found in Thailand. 相似文献