Thin-Layer Chromatography

60 3 Chemical Methods of Detection
Table 10 (Continued)
Substances Method, reagent and end products References
Alkaloids
Strychnine, brucine
Polyaromatic hydrocarbons
(PAH)
Reductions
a) 10% chromic acid in glacial acetic acid is ap- [2]
plied on top of the sample spot Development is
performed after a brief reaction period
b) Dehydration by heating the applied sample [18, 19]
solution on silica gel layers
Oxidation is performed with potassium [17]
dichromate solution This oxidizes brucine to the
o-quinone which can then be separated
chromatographically
a) Apply the sample solution, spray with [20]
tnfluoroacetic acid solution, heat to 100°C, cool
and develop Tnfluoroacetic acid catalyzes oxidation
by atmospheric oxygen
b)Apply sample solution and place in an iodine [21]
chamber for several hours, allow the iodine to
evaporate 3,4-Benzpyrene forms, for example,
ft«-3,4-benzpyrenyl
Steroids The applied steroids are reduced by means of a [3]
mixture of 10% ethanolic sodium borohydride
solution and 0 1 N sodium hydroxide solution
(1 + 1) The excess reagent is neutralized with acid
after 30 mm
Strychnine
Oleanomc acid,
tigogenone
7-Ketocholesterol, sterol
hydroperoxides
Alkaloids
Sample applied as spots followed by 5% sodium [22]
borohydnde solution, which is then dried and followed
by development
Apply sample and then treat with 10% sodium [16]
borohydnde solution in methanol—water (1 + 5)
Spray TLC plate with methanol and store in a
desiccator at 55 °C for 1 5 h over ethanol —methanol—dioxan
(4 + 1 + 1), then dry the TLC plate
(drying cupboard) and develop Oleanohc acid
and tigogemn are produced
The applied sample is treated with 1 % methanolic [23, 24]
sodium borohydnde After allowing reaction to
proceed for 5 mm the TLC plate is dned and then
developed
Sodium borohydnde solution is applied after the [2, 25]
sample solution The plate is dried and developed
after a few minutes
Table 10 (Continued)
3 1 In Situ Prechromatographic Denvatization 61
Substances Method, reagent and end products References
Disulfides
Methyl glycyrrhetate,
diosgenin
Fatty acids
Maleic, fumanc,
glutacomc, citraconic,
mesacomc and ltacomc
acid
Amino acids
Nitro compounds
1 Nitropyrene
Tetrazohum salts
The applied sample solution is treated with 0 4% [26]
sodium borohydnde solution in 95% ethanol
After 15 to 20 mm reaction time the excess reagent
is destroyed with acid
Apply 5% palladium or platinum chlonde in 50% [16]
hydrochlonc acid to the start, then spray with
alkaline formaldehyde solution and dry in air,
spray with 5% acetic acid solution and dry at
80 °C Then apply the sample solution and lightly
spray with ethyl acetate Store the TLC plate for
50 to 72 h in a desiccator over ethyl acetate in a
slight stream of hydrogen, then dry and develop
The product is, for example, methyl desoxyglycyrrhetate
Apply 1 drop colloidal palladium solution to the [27, 28]
start zone and dry at 80 to 90°C for 60 min Then
apply the sample solution, store the TLC plate for
60 min in a hydrogen-filled desiccator, then dry
and develop
Apply colloidal palladium solution to the starting [29]
point (diameter 8 to 10 mm) and dry Then apply
sample solution and gas with hydrogen (desiccator)
for 1 h Maleic and fumanc acids yield succinic
acid etc , which may also be separated
chromatographically
The configuration was determined by reacting [30]
with a carbobenzyloxy-L-amino acid azide and
reductively removing the protective group with
hydrogen/palladium chlonde solution
The sample was applied, followed by 15% zinc [31]
chlonde solution and dilute hydrochloric acid
The reaction was allowed to proceed for a short
time, the plate was then dned and the amino compounds
so formed were chromatographed
Extracts of diesel exhaust gases were applied to [32]
concentrating zone, platinum chlonde solution
was then applied followed by sodium borohydnde
1-Aminopyrene was formed
Formazan dyes are produced on reaction of [33]
tetrazohum salts with ammonium sulfide