Figure 12 : To find accurately - by +- 0.1 mm in X and Y coordinates the plate center: Either a piece of aluminium rod with a 5 mm o.d. lower part and a 10 mm o.d. upper part can hold a short piece of a 3 mm o.d. PTFE tube with 1 mm i.d. If this has a length of about 25 .. 30 mm it holds a capillary precisely enough in its center for a good contact to the stationary phase surface. As PTFE tubes of the sizes 5 x 3 mm and 3 x 1 mm are commercially standard, One can fit the 3 x 1 tube of 25...30 mm length into a 5 x 3 mm PTFE tube. The 3 x 1 mm tube sits 0.5 mm outside the lower end of the 5 x 3 mm tube. This “tool” is positioned into the cover glass plate. The latter is strictly positioned onto the three aluminium rods shown in the figure 12. Now we have a most simple tool which takes care, that a focus liquid capillary does its job correctly. Figures 15, 16 and 17 show in series the power of correct focussing. Sample positions and spot types / sizes can of coarse also given accurate, see the next figure. Click onto the right arrow above.
