Synchronized Cyclic Capillary Electrophoresis SCCE

FIGURE 6.26 Fluorescence image of unmodified PDMS COMOSS column (lOx) following incubation with rhodamine 110 for 2 days [360]. Reprinted with permission from Wiley-VCH Verlag. 

FIGURE 6.28 The principle of SCCE. Three groups of samples are given by the circled numbers 1, 2, and 3. The voltage-switching procedure is synchronized to group 2. (a) injection phase (b) during phase 1 (c) at the end of phase 1 (d) phase 2 (e) phase 3 (f) end of the cycle [648]. Reprinted with permission from Elsevier Science. 

A new layout in SCCE was reported. This permits the investigation of sample behavior at corners and T-junctions. Improved resolutions are found for FITC- 

FIGURE 6.29 Electropherogram obtained using SCCE for a FITC sample and its degradation products. The synchronization speed was adjusted to the first two eluting peaks A and B. Time intervals with forward motion at the detector are indicated by the black bars. After one cycle, the components A and B appear again (80,000 theoretical plates, resolution 3.0) [648]. Reprinted with permission from Elsevier Science. 

Another variation of SCCE is field-inversion electrophoresis. A sample (e.g., DNA) was passed back and forth within a short length of a microchannel. Using an alternating potential (600 V of several Hz) applied over an 8-mm channel, this method can provide a similar resolution to that of a significantly longer micro-channel. The inverting field serves to disrupt DNA alignment (reptation) with the electric field and hence recovers the size-dependent separation [651], 

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Burggraf, N., Manz, A., Verpoorte, E., Effenhauser, C.S., Widmer, H.M., de Rooij, N.F., A novel approach to ion separation in solution synchronized cyclic capillary electrophoresis (SCCE). Sensors Actuators B 1994, 20, 103-110. 

Synchronous cyclic capillary electrophoresis (SCCE) was proposed by Jorgenson s group as a technique which allows overcoming the dispersion problems in FCCE caused by the parabolic counterflow profile [31], High resolution is achieved in SCCE by driving the samples in a virtually closed loop until desired resolutions are achieved. This technique was applied for isotopic and chiral separations. In the third cycle, the chiral compound (a-hydroxybenzyl) methyltrimethylammonium with a selectivity as low as 1.0078 was almost baseline separated in 3.5 h [40]. As mentioned by the authors, similar separations with a multicycle LC system as described in [41] would also be possible but would have taken 43 h. 

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