Syringe pump operations

A high pressure syringe pump operated under constant pressure mode Is often used for low flow rate operation In narrow-bore packed column HFLC. Flow rates as low as 0.05 Mi /nln can be obtained. The drawback of constant pressure operation Is the potential flow rate variation due to a flow resistance change In the column. 

The model of dilution experiment is depicted in Fig. 6.19. Prior to injection sequence, there is grams of pure solvent in the calorimetric cell. Then, small aliquots of the stock solution of molality are injected by the syringe pump operating at a constant flow rate dpump- When the time of injection tinj is maintained constant, the amount of the solute n " introduced into the calorimetric cell is always the same. As a result, the equilibrium solution in the cell becomes more and more concentrated, i.e., m. The dilution data may be further processed in two... 

The hydrophilic Au SR (RSH = GSH, h-GSH, (PG)SH, (SA)SH) clusters were ionized by the ESI method [15,16,18,23,24] (Figures 2 and 3c). The details of the ESI source are depicted in Figure 3c, together with typical pressures of the chambers under operation. A 50%(v/v) water-methanol solution of the fractionated Au SR cluster with a typical concentration of 0.5mg/mL was electro-sprayed into the ambient atmosphere through the stainless steel needle of a syringe biased at ca. — 3kV. The solution was delivered by a syringe pump (SP310I, World Precision... 

The processor was operated at atmospheric pressure and at 117—130 °C or 200 °C. A methanol-water mixture (1 1.5 molar ratio) was fed at 0.1 cm /h using a syringe pump. The reactors loaded with powder and pellets had comparable results, but the researchers preferred the powder packed bed form for its smaller volume and mass. The best hydrogen production was obtained at low temperatures, providing, on a dry gas basis, 70% hydrogen, 0.5% carbon monoxide, and residual carbon dioxide. Methanol conversion or thermal efficiency was not reported. 

Controlled by the MS-MS software, the PE Series 200-micro LC pump operates iso-cratically using 80% acetonitrileiwater at 40 pl/min. A 50 x 1 mm C18 column (Keystone) is used between the pump and autosampler to provide back-pressure. The syringe/system flush solution is the 80% acetonitrileiwater used as the mobile phase. The autosampler is connected directly to the MS-MS Turboion Spray source. The injected sample volume is 20 pi. 

Figure 11 -5 shows an autotitrator, which performs the entire operation automatically.4 Titrant from the plastic bottle at the rear is dispensed in small increments by a syringe pump while pH is measured by electrodes in the beaker of analyte on the stirrer. (We will learn how these electrodes work in Chapter 15.) The instrument waits for pH to stabilize after each addition, before adding the next increment. The end point is computed automatically by finding the maximum slope in the titration curve. 

Specimens of catalysts (0.125 gram) were deactivated at 360° C for desorption experiments by using continuous (rather than pulsed) operation. Purified liquid benzene or cumene was pumped to the injection port of the microreactor system with a syringe pump at the rate of 0.00241 moles/hour. Propylene was fed from a gas lecture bottle through a rotameter at a rate of 0.00245 moles/hour. Parent H-mordenite catalyst samples were de-... 

Whereas much mechanistic information can be obtained by one of the above methods, any practical applications must be demonstrated under conditions similar to process operation, i.e., continuous flow. Small glass reactors which allow controlled addition of reagents by syringe pump and continuous removal and monitoring (IR spectroscopy) of product mixture have been developed. Much of the information obtained from semibatch operation has been reproduced under these continuous flow conditions. 

A reversed-phase HPLC column (typically Cl 8 or C30) is required for HPLC separations. Because the flow rate into the continuous-flow FAB-MS or LSIMS source must be <10 pl/min, either a capillary column must be used or else the flow must be split postcolumn. For narrow-bore HPLC columns operated at 200 pl/min, the split ratio would be 30 1. Isocratic or gradient separations may be used. A syringe pump is usually necessary for capillary columns, but standard HPLC pumps are sufficient for applications using narrow-bore columns. 

Autofill Valve. The VALCO autofill valve and actuator is an option available on the Suprex Model 50 extractor that presented problems during routine operation even without the multi-vessel adaptations. With the multi-vessel option, rapid refill of the syringe pump is a necessity for routine unattended operation. This is accomplished via a VALCO 1/16 five port valve (Model E04) mounted on an electric actuator. The valve has a pressure rating of 11,000 PSI. In the tank mode, the autofill valve directs flow from the mobile phase tank to the pump. In the column mode, flow is directed from the pump to the column. 

Briefly the positions of the valve are used in a manner illustrated in Figure 3. Position 1 is fitted to a 1/16" stainless steel tee (T3) fitting for delivery of fluid from the system syringe pump to the two 6-port tandem selectors for 12 column operation. In the 6 column system, this tee is eliminated. If six column operation is desired on the twelve column system, an on/off valve placed in line with one of the exit tubes (OU-4) from the stainless steel tee is manually closed and single delivery to one tandem selector is achieved. Position 2 of the VALCO selector valve delivers modifier from the liquid pump to each one of the extraction vessels automatically. 

We have demonstrated in this paper that two and four samples can be extracted in parallel with supercritical carbon dioxide without significant impact on data quality. Modifications made to an off-line extractor involved addition of a multiport manifold for the distribution of supercritical fluid to four extraction vessels and of a 12-port, two-way switching valve that allowed collection of two fractions per sample in unattended operation. The only limitation that we have experienced with the four-vessel extraction system was in the duration of the extraction. When working with 2-mL extraction vessels and 50-/zm restrictors, and using the pressure/temperature conditions mentioned above, the 250-mL syringe pump allows us a maximum extraction time of 60 min. During this time, two 30-min fractions can be collected with the present arrangement. 

Off-Line Systems Flowing FS- and HF-MMLLE systems are usually operated by pumping the sample solution on the sample side of the membrane, which can be done with a peristaltic or syringe pump. The stagnant or flowing organic solvent is supplied by another similar pump to the acceptor channel and membrane pores. 

The experimental apparatus and technique has been described in detail elsewhere.(20>21) The retention factors of naphthalene and biphenyl under isothermal conditions at various pressures were obtained using capillary columns coated with a cross-linked phenyl polymethylphenyl-slloxane stationary phase with carbon dioxide as the fluid mobile phase. A Varian 8500 syringe pump was operated under computer control providing accurate, pulsefree control of the fluid pressure. 

Beesley21 has described some special development chambers designed for nonconventional TLC operation. Camag has produced an automated radial system whose operation closely approximates that used in column LC. A syringe pumps mobile phase into the center of a plate, and a sample is injected into the flowing stream and is separated as concentric circles on the plate. 

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