Thin-Layer Chromatography

Table 17 (Continued)
Substances Method, reagent and end products References
Amines
Serotonin
Sympathomimetics with
free amino groups e g
carbadnne, norfenefnne,
noradrenahne,
norephednne
Amines, Amino acids,
peptides, e g tryptophan,
tryptamine, peptides with
terminal tryptophan
groups
Catecholamines
Habituating drugs
Desoxynbo-ohgonucleotides,
nbopolynucleotides
Aliphatic and aromatic aldehydes
Insecticides, e g eldnn,
dieldnn, aldnn
Carveol, hnalool,
geraniol, a-terpineol, nerol
etc
Apply sample solution then/7-toluenesulfomc acid [102]
in pyndine, heat to 60 °C for 4 h, after cooling to
room temperature develop the /7-toluenesulfonates
so formed
Benzoylate the amino groups by overspotting at [103]
the start This makes detection with GIBBS' reagent
possible
Apply sample solution (50 pg to 300 ng) Then [104]
apply fluorescamine (0 03% in acetone), dry and
chromatograph
Apply indole derivatives dissolved in sodium bo- [105]
rate buffer solution (c = 0 2 mol/1, pH 9 0) -
ethanol (1+1) Dip TLC plate in fluorescamine
solution to just above starting zone (15 s) Then
dry at room temperature and develop In case of
indole amines followed by spraying with 40% perchloric
acid
Apply sample solution followed by phosphate [105]
buffer (c = 0 5 mol/1, pH 8 0) Dip TLC plate into
fluorescamine solution to just above starting zone,
dry and develop Blue fluorescence occurs after
spraying with perchloric acid (70%)
Apply sample solution Let it react with NBD- [236]
chloride or diphenylacetyl-l,3-indandion-l-hydrazone
Layer PEI cellulose Complex formation of [106]
polyundyhc acid (6 mg/ml) with desoxyadenosine
ohgonucleotides
Apply sample solution, followed by 1 % aniline in [107]
dichloromethane and chromatograph the
SCHIFF'S bases after 10 mm
Apply the sample solution, dry and then apply [108, 109]
ethanolic zinc chloride solution, heat to 100 C for
10 min, after cooling chromatograph the carbonyl
compounds that have formed
Elimination of water with the aid of sulfunc acid [9 14]
and formation of the corresponding monoterpene
hydrocarbons
Table 17 (Continued)
Substances
Alcohols
Method, reagent and end products
Apply sample solution, then nitrophenyl lsocyanate
solution (10% in benzene) Dry after reacting
and develop
References
Other possibilities are the reduction of nitro groups by applying the sample
solutions to adsorbent layers containing zinc dust and then exposing to hydrochloric
acid vapors [110] 3,5-Dinitrobenzoates and 2,4-dinitrophenylhydrazones
can also be reduced in the same way on tin-containing silica gel phases [111]
Cellulose layers are also suitable for such reactions [112] SEILER and ROTHWEILER
have described a method of "trans-salting" the alkali metal sulfates to alkali metal
acetates [113]
3.2 Postchromatographic Detection
There is no difficulty in detecting colored substances or compounds with intrinsic
fluorescence on TLC chromatograms The same applies to components absorbing
in UV light which have been separated on layers with incorporated "fluorescence
indicators" and, hence, cause phosphorescence quenching in UV light so that the
substances appear as dark zones on a bright emitting background
Substances which do not exhibit such properties have to be transformed into
detectable substances (derivatives) in order to evaluate the TLC separation Such
reactions can be performed as universal reactions or selectively on the basis of
suitable functional groups Substance-specific denvatization is practically impossible
The aim of a postchromatographic denvatization is first
• the detection of the chromatographically separated substances in order to be
able to evaluate the chromatogram better, visually
But equally important are also
• increasing the selectivity, which is often associated with this and
[72]