Page 526 - Tandem Techniques

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sample masses of less than 100 ng (0.1-1 vmol) can provide good spectra, the concentration sensitivity
of the device is relatively poor. The experimental arrangement of the micro cell and electrophoresis
apparatus is shown in Figure 13.18.

Figure 13.18
The Experimental Arrangement of the NMR
Microprobe Electrophoresis Combination
Reprinted with permission from N. Wu, T. L. Peck, A. G.Webb,
R. L. Magin and V. Sweedler, Anal. Chem., 66(22)(1994)3849,
Copyright 1994 American Chemical Society.

The micro-coil is wound directly onto the polyimide-coated fused silica tubing, 75 mm I.D. and 355 µm
O.D. The capillary serves as both the sample chamber and the former for supporting the micro-coil. The
coil was wound with the aid of a pin vice, micro-manipulator and stereo microscope. The copper wire
was 42 gauge (63.1 µm diameter) insulated with varnish, and typically 14-17 turns of wire were placed
on the tube. To minimize susceptibility-induced static magnetic field distortions the coils were formed
with single tightly wound turns, and the bifilar winding technique was not employed. Initially, one end
of the coil was attached to