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                       µ-Planar Liquid Chrom.

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9 focusing fundam.

19focusing fundamentals

Figure 9 : Focusing fundamentals. The single and the double focusing procedure.
The figure above shows a single brown round spot. It has been sampled by one spot dipping. In a line above the brown spot are three bows and one circle. The leftmost bow has been focussed from a triple dipped round spot, which prior to focussing had to be blown dry. The bow left to the circle has been focussed from a single dipped spot like the round brown one. The circle has been focussed by touching the center of the round spot with the tip of a micro brush filled with focussing liquid. The rightmost bow has been double focussed: fist intro a circle and then into a bow. In all cases the focussing liquid was water free methanol. All focussing with bows as result have been done by putting the tip of the methanol loaded micro brush about 2 mm under the round spot or under the circle in case of the rightmost bow. Have a critical look to the details of the bow lines: The bow line ends show non uniformity. The bow lines are thick in the middle and go thinner towards the ends. Not so the rightmost bow lines: the line ends look somewhat thicker, but the inner parts of the line length are uniformly thick - theoretically, not clearly to be seen in this figure 9.By multi integration it can be shown: for accurate quantitative data we need double focussing, as a single focussed round spot shows a substance mass gradient from the bow ends to the center. This is easily to understand if one thinks of a non circular focussing process. If one would use a mechanical device for linear sampling and focussing, one would get linear sample lines of equal substance mass along the line. This we do in figure 18 in order to make the selection of mobile phases easy and with the utmost minimum of mobile phase - see figure 18 and 19.