Glass capillary, metal-coated

In this chapter, several methods for the fabrication of different types of amperometric tips suitable for SECM are described. We have also suggested some methods for microelectrode fabrication, which have not yet been tested for SECM but may provide alternative ways for its tip preparation. Section II.A describes the techniques for the preparation of various metallic microelectrodes, including Pt, Ir-Pt, Au, Hg, and W. The manufacture of carbon microelectrodes is presented in Section II.B. Most of these tips are encapsulated in or supported with glass capillaries. Other coating materials and techniques are treated in Section II.C. 

Reduction of the size of SECM probes is important, since the resolution of SECM depends strongly on the size of tip used. In order to achieve this goal, one has to thin down the diameter of commercially available metal wires by electrochemical etching or by pulling in glass capillary as described below. Further coating and exposing steps are then necessary, as in the case of unetched wires, to expose only the electrode surface. One method for the... 

The column is perhaps the most important feature of a GC system. It contains the stationary phase and thus effects the separation of components in a mixture. The column may be made of glass or metal and typically 2-6 mm i.d. and 1-3 m in length when packed with stationary phase material or 0.2-0.7mm i.d. and lO-lOOm long if in the form of a capillary column. Columns are formed into a coil of between 4 and Sin (10-20cm) in diameter and specially designed end fittings are used to connect the columns to the injector and detector with minimum dead volumes. A packed column contains solid particles of uniform size coated with stationary phase in GLC or uses uncoated particles as the stationary phase in GSC (Figure 5.4). 

The development of the flexible fused silica capillary GC column described in Section 11.5 resulted in the domination of the GC market by open tubular columns and instruments tailored to their use. Packed columns are relegated to a few special applications. Fused silica capillaries were easy to install. They were more inert (i.e., contained less active sites causing tailing) than glass or metal capillaries or the particle supports used in packed column GC. Even when the resolution of packed columns was sufficient for simple separations, a capillary coated with the same stationary phase could... 

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