Separation Syringe pump

A simple microfluidic mixer module (Fig. 3a) was designed to generate controlled mixtures of two fluidic inputs. Buffer and FITC-dextran solutions, individually controlled by separate syringe pumps, were introduced into the microfluidic device via two inputs. 

Another advantage of the micro-LC approach is that the required sample size is minimal, so the sample can be drawn from a 1-1 laboratory scale reactor without influencing the reactor composition. The ISCO pLC-500 microflow syringe pump has proven to be reliable and reproducible in evaluations in our laboratory. Capillary liquid columns have been fabricated on planar devices such as silicon to form a miniaturized separation device.19... 

Miniaturized columns have provided a decisive advantage in speed. Uracil, phenol, and benzyl alcohol were separated in 20 seconds by CEC in an 18 mm column with a propyl reversed phase.29 A19 cm electrophoretic channel was etched into a glass wafer, filled with a y-cyclodextrin buffer, and used to resolve chiral amino acids from a meteorite in 4 minutes.30 A 6 cm channel equipped with a syringe pump to automate sample derivatization was used to separate amino acids modified with fluorescein isothiocyanate.31 Nanovials have been used to perform tryptic digests on the 15 nL scale for subsequent separation on capillary Electrophoresis.32 A microcolumn has also been used to generate fractions representing time-points of digestion from a 40 pL sample.33 A disposable nanoelectrospray emitter has been... 

H202 (30%, 15 ml, 130 mmol) is fed at a constant rate of ca. 0.3 ml/min using a syringe pump into the alcohol (48 mmol), hydrated RuC13 (0.02 g, 0.077 mmol) and DDDMA-Br (0.4 g, 1 mmol). The organic phase is separated and evaporated. The crude products are purified by chromatography from silica. 

A 1-L, oven-dried, round-bottomed flask equipped with a magnetic stirrer is charged with 9.92 g (27.9 mmol) of methyl R)-3-(tert-butyldiphenylsilyloxy)-2-methylpropionate and 200 mL of dry hexanes (Note 15). The solution is cooled to -78°C, and 31.5 mL (31.5 mmol) of 1 M diisobutylaluminum hydride (in hexane) (DIBAL-H) (Note 16) is added dropwise over 15 min via a syringe pump. After the addition is complete, the resultant solution is stirred at -78°C for 2 hr. The reaction is quenched by pouring the cold solution info 250 mL of saturated aqueous Rochelle s salt. Ether (300 mL) and HjO (75 mL) are added and the biphasic mixture is stirred vigorously for 1 hr (Note 17). The layers are separated and the ether layer is washed with brine. The aqueous layer is extracted with ether (2 x 50 mL) and the combined extracts are dried over Na2S04. Filtration of the solution and concentration of the filtrate under reduced pressure followed by purification of the crude product by flash chromatography (Note 18) yields 7.85 g (86%) of (R)-3-(tert-bUtyldiphenylsilyloxy)-2-methylpropanal as a white solid (Note 19). 

Although the concentration of fluorine is the most important quantity in the control of the reaction rate and must be maintained within certain limits, in practice the stoichiometry, the molecular fluorine to substrate H-atom molar ratio, is used to determine the reaction parameters leading to a successful and efficient perfluorination. AF is most successful when sublimable solids are introduced into the hydrocarbon evaporator unit of the aerosol fluorinator as solutions by a syringe pump. This now common procedure emphasizes the individual molecule s isolation as it is fluorinated using AF. No intermolecular reactions between solute and solvent have been observed Choice of the solvent is important as it must not boil at a temperature below the melting point of the solute in order to prevent solid deposition in the tubes feeding the evaporator. It must also fluorinate to a material easily separable from the solid reactant after perfluorination. In most cases it has been found that aliphatic hydrochlorocarbons are excellent choices, but that carbon tetrachloride and chloroform and other radical-scavenging solvents are not (sec ref 6). 

To 244 mg (0.64 mmol) of the starting bromide (E/Z ratio 1 7) in dry toluene (0.015 M) under reflux was added 2.4 eq of tributyltin hydride and AIBN (catalytic amount) in 3 h through a syringe pump. The reaction mixture was cooled and the solvent was evaporated. The residue was dissolved in ether and 10% aqueous KF solution was added, and the mixture was stirred for 18 h. The organic phase was separated, dried, and evaporated. After flash chromatography (hexane-ethyl acetate, 90 10) of the residue gave the 134 mg (80%) of the product mp 75-77°C [a]D —61° (c 1.2, CHC13). Minor amounts of the noncyclized reduction product and the isomeric compound with an a-CHjCOjMe were also isolated. 

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. 

An analogous strategy was applied for annelation of ring D in Kuehne s syntheses of 20-epi- ((/-vincadifformine (96) and yz-vincadifformine (97). Upon slow addition of n-BujSnH and AIBN via syringe pump to the phenylselenyl ether 94,20-epi- vincadifformine (96) and vincadifformine (97) were formed in a 1 2 ratio. The separated products did not epimerize under the reaction conditions, indicating a facial preference in the hydrogen transfer to the pentacyclic radical intermediate 95. The ethyl substituent blocked 5-exo-trig cyclization. 

Another multisyringe FI separation system design has been used in the analysis of stable and radioactive Y, using an extraction-chromatographic material containing HDEHP adsorbed on a C18 support.123 Separated samples were analyzed off-line by ICP-AES and proportional counting. This system used four syringe pumps in parallel. 

The scheme in Figure 9.19 shows a simplification of the separation unit, using a 2-position valve to reverse the flow through the column for load/wash and elute steps, and an additional 2-position valve as a detector diverter valve. The system also incorporated several zero-dead volume syringe pumps and several additional valves to route sample and reagents through the system. 

FIGURE 9.19 Simplified schematic diagram illustrating sample preparation, separation, and detection for an on-line analyzer for the continuous monitoring of the total "Tc content of nuclear-waste process streams. A number of zero-dead volume syringe pumps and valves are not shown. 

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