Frans_M_Everaerts_Isotachophoresis_378342.pdf

208 INSTRUMENTATION
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Fig.7.4. Cross-section of the six-way valve in the ‘running’ position. 1 = Connection towards the
reservoir of the terminating electrolyte; 2 = connection towards drain; 3 = connection towards drain;
4 = narrow-bore tube in which the separation is performed; 5 = position where the syringe filed with
sample can be mounted; 6 = position where the syringe fiied with terminating electrolyte can be
mounted. Materials: a = brass; b = Amite; c = Kel-F; d = Kel-F.
tubes or movingboundary experiments. It can also be recommended for automation
purposes.
7.2.4. Injection block
A method for sample introduction with a micro-syringe is demonstrated in Fig.7.5, and
a photograph of the injection block is shown in Fig.7.6. .
The leading electrolyte can be introduced via an open tap at the side of the counterelectrode
compartment, not shown in the figure (see Fig.7.9). The tap between the
injection block and the connection towards drain (4) is opened during this procedure,
while tap (2) is closed. The tap at the side of the counter flow compartment is then
closed and tap (2) is opened. The terminating electrolyte can now flow towards drain. In
general, no suction need be applied. Next, tap (4) is closed and a ‘well’ defined boundary
is obtained between the leading and terminating electrolytes. A sample can now be
introduced via the septum (3) with a normal micro-syringe. The sample introduction can
be effected in the leading electrolyte, in the terminating electrolyte or at the boundary of
the two electrolytes, as desired.
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