Electrospray Device for Coupling Microscale Separations and Other Miniaturized Devices with Electrospray Mass Spectrometry (original) (raw)
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Microfluidic device for capillary electrochromatography-mass spectrometry
ELECTROPHORESIS, 2003
A novel microfabricated device that integrates a monolithic polymeric separation channel, an injector, and an interface for electrospray ionization-mass spectrometry detection (ESI-MS) was devised. Microfluidic propulsion was accomplished using electrically driven fluid flows. The methacrylate-based monolithic separation medium was prepared by photopolymerization and had a positively derivatized surface to ensure electroosmotic flow (EOF) generation for separation of analytes in a capillary electrochromatography (CEC) format. The injector operation was optimized to perform under conditions of nonuniform EOF within the microfluidic channels. The ESI interface allowed hours of stable operation at the flow rates generated by the monolithic column. The dimensions of one processing line were sufficiently small to enable the integration of 4-8 channel multiplexed structures on a single substrate. Standard protein digests were utilized to evaluate the performance of this microfluidic chip. Low-or sub-fmol amounts were injected and detected with this arrangement.
Analytical Chemistry, 2011
The powerful hybrid analysis method of capillarybased separations followed by mass spectrometric analysis gives substantial chemical identity and structural information. It is usually carried out using electrospray ionization. However, the salts and detergents used in the mobile phase for electrokinetic separations suppress ionization efficiencies and contaminate the inlet of the mass spectrometer. This report describes a new method that uses desorption electrospray ionization (DESI) to overcome these limitations. Effluent from capillary columns is deposited on a rotating Teflon disk that is covered with paper. As the surface rotates, the temporal separation of the eluting analytes (i.e., the electropherogram) is spatially encoded on the surface. Then, using DESI, surface-deposited analytes are preferentially ionized, reducing the effects of ion suppression and inlet contamination on signal. With the use of this novel approach, two capillary-based separations were performed: a mixture of the rhodamine dyes at milligram/milliliter levels in a 10 mM sodium borate solution was separated by capillary electrophoresis, and a mixture of three cardiac drugs at milligram/milliliter levels in a 12.5 mM sodium borate and 12.5 mM sodium dodecyl sulfate solution was separated by micellar electrokinetic chromatography. In both experiments, the negative effects of detergents and salts on the MS analyses were minimized.
2011
We report on the use of a small lightweight mass spectrometer (MS) for chemical analysis of organic material directly from solution or from the solid state with potential value in future planetary missions. The mass spectrometer used in the experiments reported here is handheld and controlled from a laptop computer through custom software. Detection and identification of small organic molecules, including some that might be prebiotics, was achieved using methods relevant to in situ and remote sensing applications. The miniature MS was equipped with a discontinuous atmospheric pressure interface (DAPI) and a home-built electrosonic spray ionization (ESSI) source. Aqueous solutions of molecules of interest were examined using the ESSI technique, while desorption electrospray ionization (DESI) was applied to examine solid samples. The system performance was characterized by direct analysis of analytes belonging to several compound classes including biotic and abiotic amino acids, purines, pyrimidines, nucleosides and peptides. Detection limits in the sub-ppm range for solutions were achieved with the atmospheric pressure sampling/ionization interface. Tandem mass spectrometry (MS 2) was successfully applied to confirm trace detection of target compounds in mixtures. Multiple stage (MS n) analysis, where n = 3-5, was employed for molecular structure confirmation and to demonstrate the high chemical specificity as well as the sensitivity of the instrumentation. The use of improved versions of this type of mass spectrometer on exploration missions could provide detailed chemical information on organic materials in physical states currently difficult to access. The high sensitivity and specificity, combined with rapid detection and the absence of requirements for sample preparation are encouraging features of the instrumentation.
International Journal of Environmental Analytical Chemistry, 2012
Hitherto analysis of chemicals in the field using mass spectrometry (MS) has been limited to analysis of non-polar and thermally stabile organic compounds using either a direct gas leak or a membrane inlet as MS interface. Recently, Professor R. Graham Cooks' group demonstrated that miniature mass spectrometers operating at elevated pressures (40.13 Pa (1 Á 10 À3 Torr)) can be combined with electrospray ionization (ESI) for analysis of polar as well as thermally labile organic compounds. We present a simple miniaturized ESI unit for analysis of small liquid samples using miniature mass spectrometry. The ESI unit operates without pumps and supplementary sheath gases, which makes it very simple to handle in the field. 20-30 mL of sample solution is simply dropped into a small cavity in the ESI unit, where after the spray is initiated by applying high voltage to it. The miniaturized ESI unit was tested in combination with a miniature mass spectrometer (the Mini 10 developed by Professor R. Graham Cooks, Purdue University, IN) and we found that common herbicides (Atrazine, Prometryne, Terbutryne and Triadimefone) could be detected with detection limits around 1 mg L À1 and with a quantitative reproducibility of þ/À30%. These characteristics, although high for environmental samples, are comparable to detection limits obtained with other ESI units used with miniature mass spectrometers and represent an early step forward towards a future field instrument. A major advantage of the capillary spray cell is its direct compatibility with micro extraction techniques for sample pre-concentration.
Instrumentation and Applications of Micro-Liquid Chromatography/Mass Spectrometry
Journal of Chromatography Library, 1985
Chromatography is a separation technique used to separate the individual compound from a mixture using a stationary and mobile phase. Discovery of chromatography is a millstone event in biomedical research. Chromatographic separation is based on the principles of adsorption, partition, ion exchange, molecular exclusion, affinity and Chirality. There are many types of chromatography available for quantitative and qualitative analysis of pharmaceutical agents, which includes Liquid Chromatography-Mass Spectrometry (LC-MS). Combination of chromatography with spectrometry is first reported in 1967 and first LC-MS system was introduced in 1980s. LC-MS is an analytical chemistry technique that combines the physical separation capabilities of liquid chromatography with the mass analysis and mass spectrometry. Mainly the LC-MS contains liquid chromatography assembly, ion generation unit/ ionization source, mass analyzer and mass spectrometric data acquisition. LC-MS is most commonly used in biomedical sciences for pharmacokinetic analysis, genetic analysis, structural elucidation, etc. The main objective of this review is to overview the principle, instrumentation and application of LC-MS.
Subatmospheric electrospray interface for coupling of microcolumn separations with mass spectrometry
Electrophoresis, 2000
A modular subatmospheric electrospray interface with fiber optic UV detection close to the electrospray tip was developed for coupling of microcolumn separation techniques with mass spectrometry. The interface was based on a liquid junction with a removable microelectrospray tip. The electrospray tip was enclosed in a subatmospheric chamber attached in front of the sampling orifice of the mass spectrometer. The inlet of the liquid junction was maintained at atmospheric pressure, and thus no pressure drop developed across the separation column. The flow rate of the electrosprayed liquid from the liquid junction reservoir was adjusted by the pressure in the electrospray chamber. In this approach, a continuous and stable electrospray could be achieved without the use of an external pump. Since the electrospray did not depend on fluid delivery from the separation column, coated capillaries without electroosmotic flow as well as capillaries with electroosmotic flow could be used for capillary electrophoresis. In addition, the interface was found to be effective with capillary liquid chromatography. The use of a fiber optic UV detector placed close to the exit of the separation column provided additional detection information and a simple means of troubleshooting. The interface did not significantly influence the quality of the separation, even with columns generating several hundred thousand theoretical plates. Peptide samples in the submicromolar concentration range were detected, corresponding to a limit of detection in the attomole range.
Journal of Chromatography A, 2000
A simple, inexpensive and disposable device for liquid-phase microextraction (LPME) is presented for use in combination with capillary gas chromatography (GC), capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). 1-4 ml samples of human urine or plasma were filled into conventional 4-ml vials, whereafter 15-25 ml of the extraction medium (acceptor solution) was filled into a short piece of a porous hollow fiber and placed into the sample vial. The drugs of interest were extracted from the sample solutions and into the small volumes of acceptor solution based on high partition coefficients and were preconcentrated by a factor of 30-125. For LPME in combination with GC, the porous hollow fiber was filled with 15 ml n-octanol as the acceptor solution. Following 30 min of extraction, the organic acceptor solution was injected directly into the GC system. For LPME in combination with CE and HPLC, n-octanol was immobilized within the pores of the hollow fiber, while the internal volume of the fiber was filled with either 25 ml of 0.1 M HCl (for extraction of basic compounds) or 25 ml 0.02 M NaOH (for acidic compounds). Following 45 min extraction, the aqueous acceptor solution was injected directly into the CE or HPLC system. Owing to the low cost, the extraction devices were disposed after a single extraction which eliminated the possibility of carry over effects. In addition, because no expensive instrumentation was required for LPME, 10-30 samples were extracted in parallel to provide a high number of samples per unit time capacity.