Solvent delivery systems syringe pumps

Figure 2.12 Schematic representation of an on-line SPE-GC system consisting of three switching valves (VI-V3), two pumps (a solvent-delivery unit (SDU) pump and a syringe pump) and a GC system equipped with a solvent-vapour exit (SVE), an MS instrument detector, a retention gap, a retaining precolumn and an analytical column. Reprinted from Journal of Chromatography, AIIS, A. J. H. Eouter et al, Analysis of microcontaminants in aqueous samples hy fully automated on-line solid-phase extraction-gas chromatography-mass selective detection , pp. 67-83, copyright 1996, with permission from Elsevier Science.

At present, reciprocating pumps are in use for conventional column LC. In micro LC both syringe and reciprocating pumps are the favored solvent delivery systems. 

Start the solvent delivery system (pump) flowing at 2.0 mL/ min. Open the solvent draw-off valve and using the syringe withdraw just enough water so that the methanol from flask B just begins to drip into flask A. Remove the syringe and close the solvent draw-off valve. 

There are three main designs of solvent delivery system (a) the reciprocating piston pump which may be of the single, dual or triple head design (b) the syringe or displacement design which delivers constant non-pulsating flow (c) the constant pressure or pneumatic pump. 

Liquid Chromatography System. The solvent delivery system was constructed of two lO-mL stainless-steel syringe pumps (MPLC Micropump, Brownlee Labs, Santa Clara, CA). By splitting the pump effluent between the mlcrocolumn and a restricting capillary (1 20-1 2000), Isocratlc separations were achieved reproduclbly at column flowrates as low as 0.005 pL/mln, and gradient separations as low as 0.1 pL/mln. Samples of 0.5 to 50 nL volume were Introduced by the split Injection technique with a 1- L valve Injector (Model ECI4W1., Valeo Instruments Co., Inc., Houston,... 

Syringe pump (e.g.. Harvard Apparatus, Holliston, MA, USA) or an LC solvent-delivery system. 

The most important parts of the instruments are the pumps for maintaining constant, pulseless rates of flow, the column types for the molecular weight range of analysis, and the detector system see Table 3.12. Some of the popular types of solvent delivery pumps include syringe pumps, the plunger of which is actuated by a screw-fed stepper motor, and the dual piston reciprocating pumps, which may have the pistons in either series or parallel see Figure 3.19 (79). 

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