Preparative chromatography pumps

The practices of isocratic and gradient sorptive chromatography are very different. Isocratic chromatography tends to be very sensitive to the details of mobile phase preparation, temperature, pump speed, and sample composition. Gradient chromatography is usually more tolerant of small variations in these factors but may be extremely sensitive to column history, equilibration time, and gradient preparation. 

Automation allows batch chromatography to be run as a continuous process. Multiple injections using a separate pump and fraction collection provide an opportunity for continuous unattended operation. In iso-cratic separations, sample injection is often made before previously injected product elutes from the column, thus reducing cycle time and solvent consumption. Continuous and automated processes are always used with smaller columns and lower amounts of expensive enantioselective stationary phases. One of the future goals for modern PHPLC optimization would be the creation of software that would allow computer simulation modeling of nonlinear effects in preparative chromatography. 

Injection Process transferring the desired amount of feed or sample into the mobile phase stream, just upstream of the column inlet. In analytical chromatography, it is carried out using syringes. In preparative chromatography, it is done by valve switching or by replacing the mobile phase by the feed at the pump. 

Chromatography is primarily a separation technique. If it is applied for the collection of pure material then it is called preparative chromatography, and if one fractionates with the aid of a pump on fine-particle columns, it is called modern preparative liquid chromatography. The aim is to extract as much material in as pure a state as possible. 

Preparative Chiral Chromatography The Loading Capacity of a Column The Maximum Sample Volume Sample Volume Overload Sample Mass Overload Preparative Chromatography Apparatus Solvent Reservoirs Pumps... 

To a stirred solution of iodobenzene (175 mg, 0.85 mmol) and sodium chloride (50 mg, 0.85 mmol) in NMP (2 ml), copper(l) iodide (16.2 mg, 10 mol%) was added, the mixture was heated to 90 C, and then 2-thiophenyltri-n-butylstannane (173, 320 mg, 0.85 mmol) in NMP (2 ml) was added slowly for 1 h via a syringe pump. The reaction mixture was stirred at 90 °C for 8 h, and cooled to room temperature, and saturated potassium fluoride solution was added. The mixture was extracted with diethyl ether (3x20 ml), and the combined organic layers were dried (MgS04), filtered, and evaporated in vacuo. The crade product was separated by preparative chromatography to afford 125 mg (92%) of pure 2-phenylthiophene (71). 

Samples can be placed on the column in other ways. In preparative chromatography, the sample is often very large and may be pumped directly onto the column from a sample reservoir employing a high-pressure pump similar to that used in the mobile phase supply system. Alternatively, with particularly difficult separations, the sample may be placed on the column from the eluent of a precolumn, using column switching (often described as two-dimensional chromatography). For example, the sample may be first... 

Peristaltic pumps are ideal because they do not dilute or contaminate the sample and are self-priming. Sizes are available to suit all applications. The only drawback is that they cannot develop the pressures required for hi -resolution HPLC. This is not a limitation for preparative chromatography since hi pressure columns are prohibitively expensive in any case. 

The boiling point of the. solvents should also be considered. For preparative chromatography, a high-purity and low-boiling mobile phase is preferred. On the other hand, the boiling point should not be too low because that could cause gas bubbles in the pump or detector. 

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