Pumping systems Principles

In reduced-flow LC-MS systems, the solvent flow into the spectrometer is reduced to a level where the pumping system can cope. Essentially, three such systems have been developed direct-liquid-introduction (DLI), flowing FAB [531] and electrospray [532]. An alternative approach to belt transport interfacing is to deliver the column eluate directly into the MS source and use Cl techniques. Methods based on this principle are called direct-liquid-injection systems, which are comprised of capillary flow restrictors, diaphragms,... 

A detailed description of IC is given in reference 1 however, the basic principles of the method can best be described by an example. Figure 1 schematically represents both an anion and a cation IC analysis. In both cases, the instrumentation involves a pumping system, an eluent, an injection valve, an ion-exchange separator column, an ion-exchange suppressor column and a conductivity cell. The sample is first injected into the flow system then the well known reaction equilibrium shown in Figure 1 results in the separation of sample anions or cations on the separator column (2). 

The instruments for polymer HPLC except for the columns (Section 16.8.1) and for some detectors are in principle the same as for the HPLC of small molecules. Due to sensitivity of particular detectors to the pressure variations (Section 16.9.1) the pumping systems should be equipped with the efficient dampeners to suppress the rest pulsation of pressure and flow rate of mobile phase. In most methods of polymer HPLC, and especially in SEC, the retention volume of sample (fraction) is the parameter of the same importance as the sample concentration. The conventional volumeters— siphons, drop counters, heat pulse counters—do not exhibit necessary robustness and precision [270]. Therefore the timescale is utilized and the eluent flow rate has to be very constant even when rather viscous samples are introduced into column. The problems with the constant eluent flow rate may be caused by the poor resettability of some pumping systems. Therefore, it is advisable to carefully check the actual flow rate after each restarting of instrument and in the course of the long-time experiments. A continuous operation— 24h a day and 7 days a week—is advisable for the high-precision SEC measurements. THE or other eluent is continuously distilled and recycled. 

In Hydrocyclones A Solution to Produced Water Treatment, Meldrum presents the basic design principle of a dc-oilmg hydrocy leone. System design, early operational experiences, and test results on a full-scale application in the North Sea are discussed. Oil-removal efficiency was seen to rise with increasing reject ratio up to around 1%, producing acceptable outlet concentrations Early field test results on a tension leg platform in the North Sea are discussed. Preliminary data on a pumped system are also given. 

A. Toepler Pump. The principles of operation of a Toepler pump are outlined in Fig. 5.9, where it will be noted that a system of internal check valves permits gas from the vacuum system to enter the upper chamber, and subsequently to be compressed and expelled into a gas buret. The system may be man-... 

The continuous operation of LCVD could be controlled, in principle, by the strict controls of the flow rate, the system pressure, and the discharge power. The addition of a residual gas analyzer in each pumping system is advantageous in detecting abnormality in gas flow, occurrence of leakage, etc. The addition of more sophisticated diagnostic devices, such as an optical emission spectrometer, in-line XPS, etc., is often counterproductive because the stability of performance and the maintenance requirement cycle of these devices do not match those for the continuous mode operation of LCVD. The information obtainable by these devices... 

Unit-dose and bi-dose systems are designed to deliver one or two doses into the nostril(s) (Fig. 9). As compared to multidose pump systems, unit-dose and bi-dose systems are distinguished by a different actuation principle. The dose volume is predetermined by the prefilled glass vial and sealed with a rubber stopper. The glass and rubber are the identical materials used in syringes. The benefit is an optimal protection against environmental influences. Unif-dose and bidose systems can be sterilized, and an aseptic filling procedure justifies the omission of preservatives. 

A chemical heat pump system consists in principle of two reactors H and L where the following processes proceed ... 

Fig. 1. Principle of the splitter kit for obtaining a microflow using a conventional LC pump system (courtesy of Bioanalytical Systems) See Note 1 for further description...

Similar advantages of lower woiking temperatures are obtained in the use of dehumidifying heat-pump systems, with the added bonus of lower thermal-energy use to compensate for extended drying times. The drying principle of these kilns, however, is the same as vented conventional kilns. 

Compared to other high-throughput systems in this parallel HPLC device, the use of a flow control unit with only one pumping system is a decisive factor. This setup guarantees stabilized flow in an extensible number of simultaneously operated separation columns and thus, in principle, can be combined with any other sophisticated column switching and detection system. A specific version of this instrument was adapted to preparative fractionation and purification of natural product extracts by... 

The concept of passive safety meant the use of systems based on simple physical laws more than on complex equipment. One example is represented by safety injection systems on water reactors which use gravity as a motive force and not pumps. This principle was, for example, adopted in the passive PWR AP600, certified by the NRC in 1999. It comprises a voluntary fast depressurization system of the primary circuit and the provision of a water reservoir in the containment located at an elevated position with respect to the reactor vessel. Passive cooling of the containment was also incorporated in the design. Evidently, however, neither of these new concepts nor the industrial weight of the NRC certification are sufficient to immediately convince the investors because, up to now (2005), no new AP600 has been ordered. 

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