Figure 13 : example of accurate sampling without electronic spotters. The figure shows 8 sample positions for which the red sharp circle is helpful. It was done the way as discussed in the figure captions to figure 11. The accurate center is made visible with a graphite pencil, rotating in the 5 mm hole of the cover glass plate. This is of course only precise enough if the HPTLC plate is well positioned - see the two rods left and fixed by adhesive tape - see right. Three spots are visibly more intensive: double spotted in the clock position 10:00, triple spotted in position 11:30 and 4 times spotted in position 12:30. How these spots look when focussed and how the sampling procedure is finished by gas flushing you see in the next figure 14.