Page 127 - phytochemistry general program
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Iodine vapors give brown spots on a yellow back-ground with most organic .5
substances especially unsaturated compounds. .6
Radioactive materials can be detected by autoradiography or by special
scanners.
4. Evaluation and Analysis.
Rf values (rate of flow) Rf values give idea on the rate of mobility of substances in
a particular system. Although Rf values are not always reproducible, they give idea
on the relative mobility of the separated substances.
Distance traveled by the center of the zone from starting point
R= ____________________________________________________________________________
f
Distance simultaneously traveled by the developing solvent.
ac sas
b
Rfa = a Rfb = b Rx =s a
c c s
Unlike Rf values, Rst values may bFeig. 9g: Rref aandtRexrvatluhesa. n one. Rst values should be within
0.5 to 1.5, otherwise a different standard should be used.
Distance moved by the substance
R= ______________________________________________
st
Distance moved by the standard (X)
Tailing in TLC
Instead of ideal round resolved spots, tailed or comet like spots appear.
Accordingly, sample components overlap and hence clean separations are not
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