Flow-gating interface

Figure 9.7 Schematic illustration of the flow-gating interface. A channeled Teflon gasket was sandwiched between two stainless steel plates to allow for flow into the electrophoresis capillary, either from the flush buffer reservoir or from the LC microcolumn during an electiokinetic injection.

TRANSPARENT FLOW GATING INTERFACE WITH PACKED CAPILLARY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY-CAPILLARY ZONE ELECTROPHORESIS... 

Figure 9.11 Schematic illustration of the transparent interface used to link the HPLC capillary to the CZE capillary. Reprinted from Analytical Chemistry, 69, T. E. Hooker and J. W. Jorgenson, A transparent flow gating interface for the coupling of microcolumn EC with CZE in a comprehensive two-dimensional system , pp 4134-4142, copyright 1997, with permission from the American Chemical Society.

FIGURE 5.9 The flow gating interface from Hooker and Jorgenson (1997). The cross-flow of buffer prevents LC effluent from electromigrating onto the CE capillary until an injection is desired. This figure is used by permission of the American Chemical Society. 

Lada, M.W., Kennedy, R.T. (1996). Quantitative, in vivo monitoring of primary amines in rat caudate nucleus using microdialysis coupled by a flow-gated interface to capillary electrophoresis with laser-induced fluorescence detection. Anal. Chem. 68, 2790-2797. 

FIGURE 16.6 Schematic of the clear flow gating interface. The interface was constructed in-house from a 1 in. diameter, 0.5 in. thick Lexan disk. The disk is clear, which allows direct observation of the capillaries in the stream of flush buffer. The capillaries are sleeved in 0.0625 in. o.d. Teflon tubing and this tubing is held in place by Lite Touch fittings (not shown). The cross-flow of buffer prevents LC effluent from electromigrating onto the CZE capillary until an injection is desired (reprinted with permission from Analytical Chemistry). 

Figure 5.9. Schematic diagram of the transverse flow gating interface for coupling capillary liquid chromatography and capillary electrophoresis in comprehensive two-dimensional separations. The interface is constructed from clear Lexan to allow visual positioning of the two capillary columns. (From ref. [100] American Chemical Society).

Analysis of amino acid neurotransmitters was achieved by online, precolumn derivatization with OPA. The reaction of OPA with primary amines occurs in less than 2 min. An online reactor was created by inserting a smaller capillary with the analyte into a larger capillary through, which the OPA was pumped. After the end of the smaller capillary, the analyte would be mixed with OPA and derivatized. A flow-gated interface was used for injection. The sample was swept to waste by a cross-flow buffer except when an injection was made. Then analyte was allowed to accumulate in the gap (30-50 ttm) between the reaction and separation capillaries. A small voltage, less than the separation voltage, was applied for only 200 ms to perform an electrokinetic injection. This allowed very efficient separations with only 30 ms wide peaks. 

A flow-gated interface allows sampling and injection from a continuous flow stream. 

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