Capillary continuous sampling

Zhang, H., and Caprioli, R. M. (1996). Capillary electrophoresis combined with matrix-assisted laser desorption/ionizatlon mass spectrometry continuous sample deposition on a matrix-precoated membrane target. /. Mass Spectrom. 31, 1039—1046. 

Fang, Q., Xu, G.-M., Fang, Z.-L., High throughput continuous sample introduction interfacing for microfluidic chip-based capillary electrophoresis systems. Micro Total Analysis Systems, Proceedings 5th XTAS Symposium, Monterey, CA, Oct. 21-25, 2001, 373-374. 

Fig. 9.7.15 First continuous sampling CE chip designed by Andrew Ewing s group at Pennsylvania State University, (a) Schematic of set-up and principle of operation for continuous flow CE chip used for on-line analysis. Capillary is rastered back and forth laterally at the gap entrance to a chip by linear translation stage actuated by stepper motors, where the analyte is pulled from a continuous flowing stream by EOF and continuously injected onto the chip. A multichannel detector is used to measure the migration of...

High throughput continuous sample introduction interfacing for microfluidic chip-based capillary electrophoresis systems. Micro Total Analysis Systems... 

Blittgenbach, S., Wilke, R., A capillary electrophoresis chip with hydrodynamic sample injection for measurements from a continuous sample flow. Arud. Bioanal. Chem. 2005, 383, 733-737. 

After this has been achieved the sample is flame sealed at position 1. All the glass parts and the high vacuum seal are removed under continuous cooling from the high-pressure capillary, and the filling capillary is resealed at position 2. The capillary glass sample cell is then screwed into the copper-beryllium autoclave, which is precooled, while the assembly remains in the cold bath until the assembly is complete. 

One way around this problem is to dispense with the trapping and separation stage by continuous sampling of the atmosphere around the Aermal probe. This can be achieved by using a small-bore silica-glass capillary transfer line which also serves to reduce the pressure fix)m atmospheric to that which could be accommodated by the ion source of the mass spectrometer. The capillary tube... 

Huang, X. H. and Zare, R. N., Continuous sample collection in capillary zone electrophoresis by coupling the outlet of a capillary to a moving surface, J. Chromatogr., 516,185,1990. 

Frontal analysis continuous capillary electrophoresis (FACCE) [S] + A[L] continuous sampling Empty Ah, K i,nt Ms = Msl and ns Ml Lower detection limits Weak-intermediate interactions... 

The column is swept continuously by a carrier gas such as helium, hydrogen, nitrogen or argon. The sample is injected into the head of the column where it is vaporized and picked up by the carrier gas. In packed columns, the injected volume is on the order of a microliter, whereas in a capillary column a flow divider (split) is installed at the head of the column and only a tiny fraction of the volume injected, about one per cent, is carried into the column. The different components migrate through the length of the column by a continuous succession of equilibria between the stationary and mobile phases. The components are held up by their attraction for the stationary phase and their vaporization temperatures. 

Schematic diagram of an electrospray inlet/ion source. A spray produced from the high electrical voltage (HT) on the capillary moves toward a hole in the electrical counter electrode. After removal of much solvent, sample ions continue under their momentum through the hole and then through the nozzle and skimmer, where most remaining solvent is removed.

Another development arising from FAB has been its transformation from a static to a dynamic technique, with a continuous flow of a solution traveling from a reservoir through a capillary to the probe tip. Samples are injected either directly or through a liquid chromatography (LC) column. The technique is known as dynamic or continuous flow FAB/LSIMS and provides a convenient direct LC/MS coupling for the on-line analysis of mixtures (Figure 40.2). 

Figure 2.16 Clirotnatograms of a pentane extract of a water sample containing 200 ppb of a naphtha fraction (a) sample extracted by using a continuous flow system, where a pressurized bottle was employed as the sample-delivery system (b) batch-extracted sample. Reprinted from Journal of Chromatography, A 330, J. Roeraade, Automated monitoring of organic Race components in water. I. Continuous flow exti action together with on-line capillary gas cliro-matography , pp. 263 - 274, copyrigth 1985, with permission from Elsevier Science.

The mass spectrometer sampling capillary or the dispersive infra-red analyzers used for continuous analysis and monitoring of the gas phase composition are situated between the reactor and the sampling valve, as close to the reactor as possible, in order to avoid any delay in the recording of changes in the composition of reactants or products. This delay should be taken into account when plotting simultaneously the time dependence of catalyst potential or current and gas phase concentration of the reactants or products. 

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