Precolumn flow splitter

FIGURE 1.4 Schematic of a typical nanoscale LC-MS interface system. A precolumn flow splitter is used to reduce to flow rate of a conventional pumping system to the 100-500 nL/min. The voltage for ESI is applied on the high-pressure distal side of the column using a junction electrical contact. 

One of the limitations in the use of capillary columns is an irreproducible and unstable gradient in the nL/min flow range. A few years ago, the standard procedure to achieve reliable gradients was to use precolumn flow splitting [44], Any conventional or micro-LC pumping system could serve to deliver low flow rates by using an appropriate homemade or commercial flow splitter. Currently, LC pumps for capiflary colunms have become commercially available that can couple capillary colunms directly with a nanospray source [45]. 

Fig. 3.2. System for double-column chromatography with intermediate trapping and re-injection, suitable also for direct injection of aqueous solutions. 1, carrier gas 2, pressure regulator 3, flow controller 4, vent for back-flushing S, injection port for heart-cut and back-flushing 6, precolumn (packed) 7, injection port for aqueous solutions 8, control flame ionization detector for pre-separation 9, vent for cutting 10. leak for make-up gas 11, trap 12, outlet of splitter 13, glass capillary column 14, flame ionization detector for main separation. Reproduced from [35].

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