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Nanoliter-volume ¹H NMR detection using periodic stopped-flow capillary electrophoresis

ANALYTICAL CHEMISTRY 1999年第15期71卷 3070-3076页

作者： Olson, DL Lacey, ME Webb, AG Sweedler, JV Univ Illinois Dept Chem Urbana IL 61801 USA Univ Illinois Beckman Inst Urbana IL 61801 USA

Recent advances in the analysis of nanoliter volumes using H-1 NMR microcoils have led to the application of microcoils as detectors for capillary electrophoresis (CE), Custom NMR probes consisting of 1-mm-long solenoidal microcoils are fabricated from 50-mu m diameter wire wrapped around capillaries to create nanoliter-volume detection cells. For geometries in which the capillary and static magnetic field are not parallel, the electrophoretic current induces a magnetic field gradient which degrades the spectroscopic information obtainable from CE/NMR. To reduce this effect and allow longer analyte observation times, the electrophoretic voltage is periodically interrupted so that 1-min high-resolution NMR spectra are obtained for every 15 s of applied voltage. The limits of detection (LODs;based on S/N = 3) for CE/NMR for arginine are 57 ng (330 pmol;31 mM) and for triethylamine (TEA) are 9 ng (88 pmol;11 mM). Field-amplified stacking is used for sample preconcentration. As one example, a 290-nL injection of a mixture of arginine and TEA both at 50 mM (15 nmol of each injected) is stacked severalfold for improved concentration LODs while achieving a separation efficiency greater than 50 000. Dissolving a sample in a mixture of 10% H2O/90% D2O allows H2O to serve as the nearly ideal neutral tracer and allows direct observation of the parabolic and flat flow profiles associated, with gravimetric and electrokinetic injection, respectively. The unique capabilities of CE and the rich spectral information provided by NMR spectroscopy combine to yield a valuable analytical tool, especially in the study of mass-limited samples.

关键词：精氨酸/分析氘电泳毛细管/仪器和设备电泳毛细管/方法乙胺类/分析甘氨酸/分析磁共振波谱学/方法磁力学渗透敏感性与特异性温度

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Micromachining in plastics using X-ray lithography for the fabrication of micro-electrophoresis devices

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JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME 1999年第1期121卷 13-21页

作者： Ford, SM Davies, J Kar, B Qi, SD McWhorter, S Soper, SA Malek, CK Louisiana State Univ Dept Chem Baton Rouge LA 70803 USA Louisiana State Univ Ctr Adv Microstruct & Devices Baton Rouge LA 70810 USA

Micromachining was performed in polymethylmethacrylate (PMMA) using X-ray lithography for the fabrication of miniaturized devices (microchips) for potential applications in chemical and genetic analyses. The devices were fabricated using two different techniques: transfer mask technology and a Kapton(R) mask. For both processes, the channel topography was transferred (1:1) to the appropriate substrate via the use of art optical mask. In the case of the transfer mask technique, the PMMA substrate was coated with a positive photoresist and a thin Au/Cr plating base. Following UV exposure, the resist was developed and a thick overlayer (similar to 3 mu m) of Au electroplated onto the PMMA substrate only where the resist was removed, which acted as an absorber of the X-rays. In the other technique, a Kapton(R) film was used as the X-ray mask. In this case, the Kapton(R) film was UV exposed using the optical mask to define the channel topography and following development of the resist, a thick Au overlayer (8 mu m) was electrodeposited onto the Kapton(R) sheet. The PMMA wafer during X-ray exposure was situated directly underneath the Kapton(R) mask. In both cases, the PMMA wafer was exposed to soft X-rays and developed to remove the exposed PMMA. The resulting channels were found to be 20 mu m in width (determined by optical mask) with channel depths of similar to 50 mu m (determined by x-ray exposure time). In order to demonstrate the utility of this micromachining process, several components were fabricated in PMMA including capillary/chip connectors, injectors for fixed-volume sample introduction, separation channels for electrophoresis and integrated fiber optic fluorescence detectors. These components could be integrated into a single device to assemble a system appropriate for the rapid analysis of various targets.

关键词：电泳毛细管/仪器和设备设备设计纤维光学技术过滤光学纤维聚甲基异丁烯酸 X线

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Capillary-electrode alignment by an optical-fiber connector for amperometric detection in capillary electrophoresis

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ANALYTICAL CHEMISTRY 2002年第15期74卷 3906-3910页

作者： Cheng, CW Lee, KC Chang, SS Chen, DC Yu, CM Chen, CH Natl Tsing Hua Univ Dept Chem Hsinchu 30013 Taiwan Natl Sun Yat Sen Univ Dept Chem Kaohsiung 80424 Taiwan

We describe here an electrochemical cell ideal for routine analysis of CE-EC experiments (capillary electrophoresis coupled with electrochemical detection). The cell was modified from a fiber-optic connector, named MT, which allowed frequent change and fast alignment between a pair of 4-strand fiber ribbons. The relative standard deviations of the current response and migration time for 100 muM dopamine were, respectively, 3.7 and 0.5% in five repetitive routines of disconnecting, polishing, and assembling the CE cell. The time required for alignment of the separation capillary and the working electrode was <10 s, once all components were assembled in an MT fiber-optic plug. These features enabled CE-EC users to polish the working electrode and reassemble the EC cell as in HPLC-EC. However, to accommodate the channel dimensions of the commercially available MT, a special order capillary with outer diameter of 125 mum is necessary at this stage.

关键词：儿茶酚胺类/分析电化学电极电泳毛细管/仪器和设备电泳毛细管/方法设备设计纤维光学技术光学纤维

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Characterization of a polyclonal antihapten antibody by affinity capillary electrophoresis

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ANALYTICAL BIOCHEMISTRY 2000年第2期284卷 422-426页

作者： Lin, SM Tsai, JC Hsu, SM Natl Taiwan Univ Coll Med Ctr Optoelect Biomed Taipei 100 Taiwan Natl Taiwan Univ Coll Med Dept Pathol Taipei 100 Taiwan

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Microfabricated devices for capillary electrophoresis-electrospray mass spectrometry

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ANALYTICAL CHEMISTRY 1999年第15期71卷 3258-3264页

作者： Zhang, B Liu, H Karger, BL Foret, F Northeastern Univ Barnett Inst Boston MA 02115 USA Northeastern Univ Dept Chem Boston MA 02115 USA

Two fundamental approaches for the coupling of microfabricated devices to electrospray mass spectrometry (ESI-MS) have been developed and evaluated. The microdevices, designed for electrophoretic separation, were constructed from glass by standard photolithographic/wet chemical etching techniques. Both approaches integrated sample inlet ports, preconcentration sample loops, the separation channel, and a port for ESI coupling. In one design, a modular, reusable microdevice was coupled to an external subatmospheric electrospray interface using a liquid junction and a fused silica transfer capillary. The transfer capillary allowed the use of an independent electrospray interface as well as fiber optic UV detection. In the second design, a miniaturized pneumatic nebulizer was fabricated as an integral part of the chip, resulting in a very simple device, The on-chip pneumatic nebulizer provided control of the flow of the electrosprayed liquid and minimized the dead volume associated with droplet formation at the electrospray exit port. Thus, the microdevice substituted for a capillary electrophoresis instrument and an electrospray interface-traditionally two independent components. This type of microdevice is simple to fabricate and may thus be developed either as a part of a reusable system or as a disposable cartridge, Both devices were tested on CE separations of angiotensin peptides and a cytochrome c tryptic digest. Several electrolyte systems including a transient isotachophoretic preconcentration step were tested for separation and analysis by an ion trap mass spectrometer.

关键词：氨基酸序列血管紧张素类/分析细胞色素c组/分析电泳毛细管/仪器和设备电泳毛细管/方法设备设计质谱分析法/仪器和设备质谱分析法/方法分子序列数据肽类/分析

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Integration of microfabricated devices to capillary electrophoresis-electrospray mass spectrometry using a low dead volume connection: Application to rapid analyses of proteolytic digests

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ANALYTICAL CHEMISTRY 1999年第15期71卷 3036-3045页

作者： Li, JJ Thibault, P Bings, NH Skinner, CD Wang, C Colyer, C Harrison, J Natl Res Council Canada Inst Biol Sci Ottawa ON K1A 0R6 Canada Univ Alberta Dept Chem Edmonton AB T6G 2G2 Canada

This report describes the development of a compact and versatile, micromachined chip device enabling the efficient coupling of capillary electrophoresis to electrospray mass spectrometry (CE-ESMS). On-chip separation provides a convenient means of achieving rapid sample cleanup and resolution of multicomponent samples (typically 2-5 min) prior to mass spectral analysis. A low dead volume connection facilitating the coupling of microfabricated devices to CE-ESMS was evaluated using two different interfaces. The first configuration used disposable nanoelectrospray emitters directly coupled to the chip device via this low dead volume junction, thereby providing rapid separation of complex protein digests. The performance of this interface was compared with that of more traditional configurations using a sheath now CE-ESMS arrangement where a fused-silica capillary of varying length enabled further temporal resolution of the multicomponent samples. The sensitivity and analytical characteristics of these interfaces were investigated in both negative and positive ion modes using standard peptide mixtures. The separation performance for synthetic peptides using a chip coated with amine reagent ranged from 26 000 to 58 000 theoretical plates for a sheath flow CE-ESMS interface comprising a 15-cm CE column. Replicate injections of a dilution series of peptide standards provided detection limits of 15-400 nM without the use of on-line preconcentration devices. The reproducibility of migration time ranged from 0.9 to 1.5% RSD wheras RSDs of 5-10% were observed on peak areas. The application of these devices for the analysis of protein digests was further evaluated using on-line tandem mass spectrometry.

关键词：氨基酸序列电泳毛细管/仪器和设备电泳毛细管/方法外源凝集素类/化学外源凝集素类/代谢质谱分析法/仪器和设备质谱分析法/方法分子序列数据蛋白质类/分析蛋白质类/化学蛋白质类/代谢敏感性与特异性序列分析胰蛋白酶/化学胰蛋白酶/代谢

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Electrophoresis separation in open microchannels. A method for coupling electrophoresis with MALDI-MS

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ANALYTICAL CHEMISTRY 2001年第9期73卷 2147-2151页

作者： Liu, J Tseng, K Garcia, B Lebrilla, CB Mukerjee, E Collins, S Smith, R Univ Calif Davis Sch Engn Div Math & Phys Sci Dept Chem Davis CA 95616 USA Univ Calif Davis Sch Engn Dept Elect Engn Davis CA 95616 USA

The separation of biological mixtures in open microchannels using electrophoresis with rapid and simple coupling to mass spectrometry is introduced. Rapid open-access channel electrophoresis employs microchannels that are manufactured on microchips. Separation. is performed in the open channels, and the chips are transferred to a matrix-assisted laser desorption/ionization (MALDI) source after the solvent is evaporated. The matrix (2,5-dihydroxybenzoic acid) is placed in the solution with the run buffer before the separation of the analyte components, After separation, the solvent is evaporated and the microchip is ready for MALDI-MS analysis. The microchip is placed directly into a specially designed ion source of an external source Fourier transform mass spectrometry instrument. Separation of simple mixtures containing oligosaccharides and peptides is shown.

关键词：环糊精类/分析环糊精类/分离和提纯电泳毛细管/仪器和设备电泳毛细管/方法傅里叶分析龙胆酸盐类胰激肽/分析胰激肽/分离和提纯寡糖类/分析寡糖类/分离和提纯大鼠 Sprague-Dawley 光谱法质量基质辅助激光解吸电离/仪器和设备光谱法质量基质辅助激光解吸电离/方法 β环糊精类动物男(雄)性大鼠

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Microfabricated electrophoresis chips for simultaneous bioassays of glucose, uric acid, ascorbic acid, and acetaminophen

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ANALYTICAL CHEMISTRY 2000年第11期72卷 2514-2518页

作者： Wang, J Chatrathi, MP Tian, BM Polsky, R New Mexico State Univ Dept Chem & Biochem Las Cruces NM 88003 USA

A micromachined capillary electrophoresis chip is described for simultaneous measurements of glucose, ascorbic acid, acetaminophen, and uric acid. Fluid control is used to mix the sample and enzyme glucose oxidase (GOx). The enzymatic reaction, a catalyzed aerobic oxidation of glucose to gluconic acid and hydrogen peroxide, occurs along the separation channel. The enzymatically liberated neutral peroxide species is separated electrophoretically from the anionic uric and ascorbic acids in the separation/reaction channel. The three oxidizable species are detected at the downstream gold-coated thick-film amperometric detector at different migration times. Glucose can be detected within less than 100 s, and detection of all electroactive constituents is carried out within 4 min. Measurements of glucose in the presence of acetaminophen, a neutral compound, are accomplished by comparing the responses in the presence and absence of GOx in the running buffer. The reproducibility of the on-chip glucose measurements is improved greatly by using uric acid as an internal standard. Factors influencing the performance, including the GOx concentration, field strength, and detection potential, are optimized. Such coupling of enzymatic assays with electrophoretic separations on a microchip platform holds great promise for rapid testing of metabolites (such as glucose or lactate), as well as for the introduction of high-speed clinical microanalyzers based on multichannel chips.

关键词：醋氨酚/分析抗坏血酸/分析电泳毛细管/仪器和设备酶类固相葡萄糖/分析微型计算机微电极尿酸/分析

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Use of microfluidics chips for the detection of human telomerase RNA

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ANALYTICAL BIOCHEMISTRY 2003年第2期313卷 331-334页

作者： Fuller, RA Clark, J Kretzner, L Korns, D Blair, SL Crocitto, LE Smith, SS City Hope Natl Med Ctr Duarte CA 91010 USA

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An integrated fritless column for on-chip capillary electrochromatography with conventional stationary phases

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ANALYTICAL CHEMISTRY 2002年第3期74卷 639-647页

作者： Ceriotti, L de Rooij, NF Verpoorte, E Univ Neuchatel Inst Microtechnol Sensors Actuators & Microsyst Lab CH-2007 Neuchatel Switzerland

A new polymer device for use with conventional particulate stationary phases for on-chip, fritless, capillary electrochromatography (CEC) has been realized. The structure includes an injector and a tapered column in which the particles of the stationary phase are retained and stabilized. The chips were easily fabricated in poly(dimethylsiloxane) using deep-reactive-ion-etched silicon masters, and tested using a capillary electrophoretic separation of FITC-labeled amino acids. To perform CEC, the separation channel was packed using a vacuum with 3-mum, octadecylsilanized silica microspheres. The packing was stabilized in the column by a thermal treatment, and its stability and quality were evaluated using in-column indirect fluorescence detection. The effects of voltage on electro-osmotic flow and on efficiency were investigated, and the separation of two neutral compounds was achieved in less than 15 s.

关键词：氨基酸类/分离和提纯电泳毛细管/仪器和设备电泳毛细管/方法设备设计荧光素-5-异硫氰酸盐荧光染料

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