Fused-silica capillary tubes

P 32] Pyrene (20 mM), 1,4-dicyanobenzene (40 mM) and sodium cyanide (1 M) were reacted in propylene carbonate and water. A 100 pi solution of pyrene (20 mM), 1.4-dicyanobenzene (40 mM) in propylene carbonate and a 100 pi solution of sodium cyanide (1 M) in water were fed by programmable dual-syringe pumps via fused-silica capillary tubes into a micro-channel chip [29]. Both solutions were fed with equal flow velocity. A 300 W high-pressure mercury lamp was used as light source. After passing an optical filter made of a CUSO4 solution, the whole chip was irradiated after formation of a stable oil/water interface inside. The oil phase was collected at the exit. 

Figure 9.9 Schesatic diagrans of flow-through cell. A, and solvent elimination interfar B, for SFC/FTIR. For A (1) polished stainless steel lig..v.pipe (2) zinc selenide window (3) PTFE spacer (4) viton rubber o-ring (5) graphitized Vespel nicroferrule (6) deactivated fused-silica capillary tubing (7) bolt with Allen nut (8) stainless steel end-fitting and (9) stainless steel body of flow cell.

Fujiwara, S. and Honda, S., Determination of cinnamic acid and its analogs by electrophoresis in a fused silica capillary tube, Anal. Chem., 58,1811,1986. 

Bullock, J.A. and Yuan, L.-C., Free solution capillary electrophoresis of basic proteins in uncoated fused silica capillary tubing, ]. Microcol. Sep., 3,241,1991. 

FIGURE 7.1 Scanning electron micrographs of a polystyrene-divinylbenzene monolithic column prepared in a 20-pm fused silica capillary tube (reproduced from the reference, Ivanov et al. (2003), with permission from American Chemical Society). 

FIGURE 7.3 Scanning electron micrographs of monolithic silica prepared from sol-gel methods, (a) monolithic silica prepared from TMOS in a test tube, and monolithic silica columns prepared from a mixture of TMOS and MTMS, (b) in a 50-pm fused silica capillary, (c) in a lOO-pm fused silica capillary, and (d) in a 200-pm fused silica capillary tube (reproduced from the reference, Motokawa et al. (2002), with permission from Elsevier). 

Capillary electrophoresis narrow-bore fused-silica capillary tube injection system detector recorder orVDU. 

These have now been superseded by capillary columns, which offer greatly improved separation efficiency. Fused silica capillary tubes are used which have internal diameters ranging from 0.1 mm (small bore) to 0.53 mm (large bore) with typical lengths in excess of 20 m. The wall-coated open tubular (WCOT) columns have the internal surface of the tube coated with the liquid (stationary) phase and no particulate supporting medium is required. An alternative form of column is the porous-layer open tubular (PLOT) column, which has an internal coating of an adsorbent such as alumina (aluminium oxide) and various coatings. Microlitre sample volumes are used with these capillary columns and the injection port usually incorporates a stream splitter. 

Hoyt and Sepaniak have used capillary zone electrophoresis to determine procaine in pharmaceuticals as a cation of benzylpenicillin [148]. A benzylpenicillin potassium tablet (250 mg) was treated with 20 mL of a 0.2% phenol solution (the internal standard), and dispersed in water. The solution was diluted to 500 mL, and samples were introduced into the fused silica capillary tube (70 cm x 50 gm) by siphoning. With 10 mM Na2HP04-6mM Na2B407 buffer as the mobile phase, the samples were subjected to electrophoresis at 30 kV (25 to 30 pA), and the emerging analytes detected at 228 nm within 10 minutes. 

Fused silica capillary tubes were variously coated for capillary electrophoresis. The chemical process involving a Grignard reaction is shown in equation 30. The silanol groups on the silica surface are treated with alkali, dried, convert to chlorosUanes with thionyl chloride and vinylmagnesium bromide replaces the chlorine atoms with vinyl... 

Capillary electrophoresis separation is performed in a flexible fused silica capillary tube that is filled with an appropriate buffer solution of defined pH and ionic strength (aqueous/nonaqueous). A small volume of sample (lower than 3-4% of the column volume) is needed to achieve efficient separation. This volume is introduced hydrodynamically (or less often electrokinetically) into the capillary to which an electrical potential is applied (Figure 13.7). Charged species of the sample exhibit... 

Instead of using a planar molding master, a fused silica capillary tube (50 pm i.d. and 192 pm o.d.) was used as a template for casting PDMS channels, and as the fluid inlet/outlet tubes. After PDMS curing, the middle pre-scored section (4 cm) of the capillary was removed to reveal the PDMS channel (192 pm wide and deep) [817]. Similarly, a capillary was used to mold a PDMS channel, and to produce an electrospray emitter. In this case, after PDMS curing, the last 0.5-cm section of the capillary was removed to create a channel [821]. 

Treat a fused-silica capillary tube (50-100 pm I.D., 370 pm O.D.) with 1M NaOH solution at 40°C for 3 h, prior to the silica preparation. 

Force the resulting mixture into the fused-silica capillary tube, and allow it to react overnight at 40°C. 

Figure 1.3. Thin fused silica capillary tubes similar to (and frequently smaller than) those shown here are often used for the analytical-scale separation of complex mixtures by chromatography and electrophoresis. The inside diameters of these capillaries are only 220 /im (lower two) and 460 fim (upper). The diameters of the smaller tubes are 680 times less than that of the LC column shown in Figure 1.2. The cross-sectional area, roughly proportional to separative capacity, is over 400,000 times less. (Photo by Alexis Kelner.)...

Figure 1.4. High-resolution separation of free fatty acids of indicated carbon numbers by supercritical fluid chromatography using a compressed C02 mobile phase at 170°C. Column is SO cm long fused silica capillary tube of 250 pm internal diameter. (Courtesy of Frank J. Yang.)...

A complex PMMA-based fluidic device was built by Soper s research group [68], which coupled capillary nanoreactors to microseparation platforms (electrophoresis chips) for the generation of sequencing ladders and PCR products. The nanoreactors consisted of fused silica capillary tubes with a few tens of nanoliters of reaction volume, which can be interfaced wiht the chips via connectors micromachined in PMMA, using deep X-ray etching. A DNA tem-... 

The technique of hpce, or ce, involves high-vOltage electrophoresis in narrow-bore fused-silica capillary tubes or columns and on-line detectors similar to those used in hplc (p. 123). Components of a mixture injected into one end of the tube migrate along it under the influence of the electric field (potential gradient) at rates determined by their electrophoretic mobilities. On passing... 

Figure 2. Schematic drawing of SDS-removal precolumn directly connected to CIS revo phase HPLC column. The resins were packed in fused silica capillary tubings which were connected by epoxy glue. The length of the column was t)pically between 200 and 2S0 mm depending upon their inner dimensions.

Another factor which has improved the quality of the capillary columns a great deal and encouraged their application, is the achievement in chemically bonding the liquid phase to the internal surface of the fused silica capillary tubing. Capillary columns of extraordinarily high quality and capability have resulted from improved quality of the liquid phases ami cross-linking of liquid phases. 

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