Mechanical pumps connection

Electroosmotic flow (EOE) is thus the mechanism by which liquids are moved from one end of the sepai ation capillai y to the other, obviating the need for mechanical pumps and valves. This makes this technique very amenable to miniaturization, as it is fai simpler to make an electrical contact to a chip via a wire immersed in a reservoir than to make a robust connection to a pump. More important, however, is that all the basic fluidic manipulations that a chemist requires for microchip electrophoresis, or any other liquid handling for that matter, have been adapted to electrokinetic microfluidic chips. 

If the pump is a filter pump off a high-pressure water supply, its performance will be limited by the temperature of the water because the vapour pressure of water at 10°, 15°, 20° and 25° is 9.2, 12.8, 17.5 and 23.8 mm Hg respectively. The pressure can be measured with an ordinary manometer. For vacuums in the range lO" mm Hg to 10 mm Hg, rotary mechanical pumps (oil pumps) are used and the pressure can be measured with a Vacustat McLeod type gauge. If still higher vacuums are required, for example for high vacuum sublimations, a mercury diffusion pump is suitable. Such a pump can provide a vacuum up to 10" mm Hg. For better efficiencies, the pump can be backed up by a mechanical pump. In all cases, the mercury pump is connected to the distillation apparatus through several traps to remove mercury vapours. These traps may operate by chemical action, for example the use of sodium hydroxide pellets to react with acids, or by condensation, in which case empty tubes cooled in solid carbon dioxide-ethanol or liquid nitrogen (contained in wide-mouthed Dewar flasks) are used. 

As mentioned in Section 5.1.B, the transmission of vibration from the mechanical pump to a vacuum rack decreases the accuracy of manometer readings. To minimize this problem, it is generally best to mount the pump on the floor below a vacuum rack and to connect the pump to the system with a short length of heavy-walled rubber tubing, Tygon tubing, or flexible metal tubing. 

Disposable pTAS will be ideal for medical use [14]. However, the high fabrication cost of sophisticated pTAS including micropumps and microvalves is a real problem. One of the basic components of medical pTAS taking this into account is illustrated in Fig. 2. A detector cell consists of micro sensors and a 3-way microvalve is placed at the sample inlet. Flow is controlled by a suction pump and an injection pump connected to the detector cell. The calibration solution flow is also controlled by an individual pump and a 3-way valve. In this system, only sample flow reaches the detector cell. The upper parts of the system are free from contamination and corrosion so that they can be reused many times, while the detector cell has to be disposed of. To realize this system, a 3-way microvalve which can handle whole blood is indispensable. A separable channel type microvalve whose channel part is disposable while actuator part is reusable is useful for the 3-way microvalve of the detector cell [15]. Mechanically fixed stack structures including disposable parts are useful in many medical pTAS. 

The oxidation process was carried out in a home-made, vacuum furnace which included a quartz container included in a furnace. The quartz container was evacuated with a high-vacuum system composed to diffusion pump and a mechanical pump. The system was connected to a sensitive manometric manifold to measure the pressure of the oxidant gas [39],... 

In many labs it is standard to use red heavy-wall rubber tubing to connect mechanical pumps to vacuum systems. However, there is no technical reason for using red (colored) tubing. Any tubing that meets the qualifications for vacuum work (or your specific vacuum work) should suffice, regardless of color. 

Aside from the two types of rotary pumps mentioned, you will often see the terms single-stage and double-stage mentioned in the context of pumps. A two-stage pump (also called a compound pump) simply refers to a mechanical pump that has one or two pumps connected in line together. The exhaust of the first one... 

Before shutting off a mechanical pump, the pump should be vented to atmospheric pressure. Although some mechanical pumps (and essentially all new pumps) have a check valve designed to prevent reverse flow, it is not a good idea to depend on such a valve. If a vacuum is held on the inlet side of a pump with the pump off, the pump oil may be drawn up and into the vacuum line. Therefore, it is best to treat all pumps as if they did not have such a valve. When turning off a mechanical pump, it is best to vent (to the atmosphere) the section of the vacuum line connected to the pump. Your pump should be separated from the rest of the line when venting so that the rest of the line is not exposed to the atmosphere. If... 

Compute the size of the connection pipe. In usual vacuum-pump practice, the pressure drop in pipes serving mechanical pumps is not allowed to exceed 20 percent of the inlet pressure prevailing under steady operating conditions. A correctly designed vacuum system, where this pressure loss is not exceeded, will have a pump-down time which closely approximates that obtained under ideal conditions. 

Figure 10-8. Equipment needed for lyophilization or freeze drying small samples, (a) The unit is cooled and evacnated by means of a self-contained refrigeration system and vacuum pump. Sample vessels are inserted into the rubber nozzles and the valve (little white knobs) opened for each nozzle that contains a vessel, (b, c) The units are evacuated by connecting them to a mechanical vacuum pump (connection indicated by arrows) and... 

Figure 1. Vacuum line and transfer system for the determination of single stage fractionation factors and composition of the phases (1) storage hulb for purified NO (2) manometer (3) silica gel tube for further purification of NO (4) gas burette containing mercury covered with a layer of a-bromonaphthalene (5) manometer (6) equilibrium vessel (7) connection for mechanical pump (8) connection for sample tube (9) stainless steel Helicoid gage (10) connection to mercury diffusion pump...

The connection of the pumping system to the manifold should be by way of a large-size trap (Fig. 3-10), which is cooled with liquid nitrogen in order to remove contaminants. In operation, the mechanical pump is started first, the pressure in the system is reduced below 100 /X, and the diffusion pump is turned on. Once a low pressure has been attained, the pumps are not ordinarily shut off unless this becomes necessary for maintenance or repair. If the system to which the pumps are connected is to be raised to atmospheric pressure regularly, a bypass system should be supplied so that the system may be evacuated... 

The Finnigan chemical ionization source was modified by the addition of two cartridge heaters. Eluate entered the source through a heated 1/2" probe and excess solvent was removed by a mechanical vacuum pump connected directly opposite the eluate entrance. The interface consisted of 1 meter deactivated silica capillary tubing (ID, 60 OD, 0.008"), led from the outlet of microbore column and threaded through the probe. The probe design has been previously described (26). For all analyses, the probe was operated at 240 C and the source at 250 C. The analyzer pressure was 10 b torr. 

The Roots pump is always connected to a mechanical pump, which provides a second-stage pumping between it and the atmosphere. The pressure difference... 

About 12 g of salt was used in each boiling point experiment. The apparatus was evacuated by a rotary fore-pump and an oil-diffusion pump, enabling to reduce pressure to about 10—3 Pa. The inert gas pressure was measured by a U-tube mercury manometer and could be adjusted by use of a valve connected to the mechanical pump. The sample was kept overnight at 200°C before measuring the mass losses at different inert gas pressures at a constant temperature. 

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