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TLC detection reactions
Please note, that these reagents are not supplied by MACHEREY-NAGEL
A B C D E F G H I L M N P R S T V
4-Aminoantipyrine/potassium hexacyanoferrate(III)
(Emerson reagent) for detection of phenols and aryl amines
Solutions:
1. 1 g aminoantipyrine (4-aminophenazone) in 100 ml 80 % ethanol
2. 4 g potassium hexacyanoferrate(III) in 50 ml water, fill up to 100 ml with ethanol
Procedure:
– spray with solution 1
– dry 5 minutes with warm air
– spray with solution 2
– again dry 5 minutes with warm air
– place chromatogram in a chamber with vapour from 25% ammonia solution, making sure that the layer does not contact the liquid
2-Aminoethyl diphenylborate see under Ethanolamine diphenylborate
Ammonium metavanadate, ammonium monovanadate see under Vanadium(V)/sulphuric acid reagent
Ammonium molybdate for detection of phosphoric acid derivatives
Solutions:
1. 1 M perchloric acid in water/acetone (1:1)
2. ammonium molybdate solution:
5 g (NH4)6Mo7O24 · 4 H2O in 35 ml semi-concentrated nitric acid and 65 ml water
3. tin(II) chloride solution: 0.5 g SnCl2 · 2 H2O in 100 ml 0.5 M hydrochloric acid
Procedure:
– dry developed chromatogram and heat to 60 °C
– hydrolyse di- and triphosphates by spraying perchloric acid (solution 1) onto the warm plate.
After spraying 2 times, dry plate slowly at 50 °C. Amidophosphates e.g. need not be decomposed.
– in any case spray the still warm plate with ammonium molybdate solution (solution 2)
– then spray the still wet plate with tin(II) chloride solution (solution 3). Phosphates appear as blue to blue-green
spots. Polyphosphates can also be detected by dipping the plates in a solution of ammonium molybdate (1 g) dissolved in water (8 ml) and perchloric acid (3 ml, ca. 70%), filled up to 100 ml with acetone. Then phosphates appear as yellow-green spots on a blue background. Also see Molybdenum blue reaction according to Dittmer and Lester
Aniline phthalate spray ragent for detection of reducing sugars
Procedure:
– dry the developed chromatogram
– spray with aniline phthalate spray reagent
– briefly dry with hot air
– heat to 80 – 130 °C for 20 to 30 min
Resulting substance spots show different colours on an almost colourless background. Some spots give a fluorescence at 365 nm.
Anisidine phthalate reagent for detection of carbohydrates
– spray with a solution of 1.23 g p-anisidine and 1.66 g phthalic acid in 100 ml 95% ethanol
Hexoses yield green, methylpentoses yellow-green, pentoses purple, uronic acids brown spots.
Boute reaction for detection of phenols
Procedure:
– dry and heat the developed chromatogram
– place hot plate for 3 – 10 minutes in a chamber with NO2 vapour (from conc. nitric acid)
– then treat with NH3 vapour (from conc. ammonia)
Bromine/carbon tetrachloride for detection of organothiophosphorus pesticides
– place chromatogram in a chamber with 10% bromine/carbon tetrachloride without contact of the liquid
Bromocresol green for detection of acids
– dip chromatogram in a solution of 0.1 g bromocresol green in 500 ml ethanol and 5 ml 0.1 M sodium hydroxide
solution
Acids yield yellow spots on blue background
Chloranil reagent for detection of phenols
– spray with a solution of 1% tetrachloro-p-benzoquinone in benzene or toluene
Chlorine/ o-tolidine for detection of compounds forming chloroamines,
e.g. urea derivatives, carbamates, antibiotics
Solutions:
1. 160 mg o-tolidine in 30 ml glacial acetic acid, filled up to 500 ml with dist. water, plus 1 g potassium iodide
2. saturated solution of o-tolidine in 2% acetic acid/0.85% potassium iodide solution (1:1, v/v)
Procedure A:
– place chromatogram 15 – 20 minutes in a chlorine atmosphere
(e.g. 1.5% potassium permanganate + 10% hydrochloric acid)
– leave 5 minutes at ambient temperature until the chlorine is evaporated completely
– spray with solution 1
Procedure B (according to Greig and Leaback)
– spray with 2% potassium hypochlorite solution in water
– leave 1 – 1.5 hours at ambient temperature
– spray with solution 2
DDQ reagent (dichlorodicyanobenzoquinone) for detection of phenols
– spray with a solution of 2% 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in benzene or toluene
Dichlorofluorescein reagent for detection of sweeteners saccharin and cyclamate
– spray with a 0.2% solution of dichlorofluorescein in 96% ethanol
– dry with warm air
– if necessary spray with water
– view under UV at 360 nm
Dichlorofluorescein/fluorescein sodium salt for detection of N-substituted barbiturates
– spray with a 0.1% ethanolic solution of dichlorofluorescein
– then spray with a 0.1% ethanolic solution of the fluorescein sodium salt
2,6-Dichloroquinone-4-chloroimide for detection of antioxidants, phenols, primary and secondary aliphatic amines, secondary and tertiary aromatic amines, aromatic hydrocarbons, pharmaceuticals, phenoxyacetic acid herbicides etc.
– spray with a freshly prepared 0.5 – 2% solution of 2,6-dichloroquinone-4-chloroimide in ethanol
– heat 10 minutes to 110 °C
– treat with ammonia vapour
p-Dimethylaminobenzaldehyde / hydrochloric acid reagent (Ehrlich's reagent)
for detection of amines, indole derivatives
– spray with a solution of 1% p-dimethylaminobenzalde-hyde in conc. hydrochloric acid/methanol (1:1)
– heat plates 20 min to 50 °C
Dithizone for detection of metal ions
Solution:
Dissolve 20 mg dithizone in 100 ml acetone, store in a brown bottle in a refrigerator.
Procedure:
– spray with dithizone solution
– spray with 25% ammonia solution
Dittmer and Lester see Molybdenum blue reaction
Dragendorff reagent for detection of nitrogen compounds, alkaloids, antiarrhythmic drugs, surfactants
Solutions:
1. 1.7 g basic bismuth nitrate and 20 g tartaric acid in 80 ml water
2. 16 g potassium iodide in 40 ml water
Stock solution (stable several weaks in a refrigerator):
mix equal volumes of solutions 1 and 2
Procedure:
– spray with a solution of 10 g tartaric acid, 50 ml water and 5 ml stock solution
Ethanolamine diphenylborate – (flavone reagent according to Neu), e.g. for flavonoids
– spray with a 1% solution of ethanolamine diphenylborate in methanol
– spray with a 5% ethanolic solution of polyethylene glycol for fluorescence stabilisation
– irradiate 2 minutes with intense UV (365 nm)
– view under UV at 365 nm
Ehrlich's reagent see p-Dimethylaminobenzaldehyde
Emerson reagent see 4-Aminoantipyrine/potassium hexacyanoferrate( III)
Fast Blue B reagent for detection of cannabinoids, phenols, tanning agents, amines which can be coupled
– spray with a solution of 0.5 g Fast Blue B [tetraazotised di-o-anisidine] in acetone/water (9:1, v/v), always prepared fresh
– spray with 0.1 M sodium hydroxide solution
Flavone reagent acc. to Neu see under Ethanolamine diphenylborate
Fluorescamine for detection of primary and secondary amines, peptides and sulphonamides, e.g. nitrosamines after photolysis
– spray plate with a solution of 0.1 mg/ml 4-phenyl-spiro[furan-2(3H),1-phthalan]-3,3-dione in acetone, prepared
fresh daily
– for stabilisation of fluorescence at 366 nm spray with 10 g triethylamine, filled up to 100 ml with dichloromethane
Formaldehyde/sulphuric acid for detection of alkaloids, aromatic hydrocarbons, e.g. antihypertensive drugs
– spray with a solution of 37% formaldehyde in conc. sulphuric acid (1:10)
Gibb's reagent for detection of phenols. For further applications see 2,6-Dichloroquinone 4-chloroimide.
– spray with a solution of 2% 2,6-dibromo-N-chloro-p-benzoquinone imine in benzene or methanol
Hydroxylamine/iron(III) chloride for detection of amides, lactones, carboxylic acid esters and anhydrides
Solutions:
1. mix 1 vol. part of 7 g hydroxylammonium chloride in 100 ml methanol with 1 vol. part of a solution of 7.2 g potassium hydroxide in 100 ml methanol. Filter from precipitated potassium chloride.
2. 2% solution of iron(III) chloride in 1% aqueous hydrochloric acid
Procedure:
– spray airdried plate first with solution 1, then with solution 2.
Iodine compounds
– detection by decomposition under UV
– dry plates at 100 °C
– after cooling spray with little 50% acetic acid
– irradiate some minutes with unfiltered UV light
Iodine compounds show weakly violet to brown spots. The colour can be enhanced by spraying to transparency with
10% acetic acid and irradiation with UV light (sudden appearance of blue spots)
Iodine vapour, relatively unspecific universal reagent for many organic compounds
– charge chamber with some crystals of iodine
– place developed, dried chromatogram in I 2 atmosphere
Iodoplatinate reagent for detection of organic nitrogen compounds, alkaloids, e.g. cocaine metabolites
– spray with a freshly prepared mixture of 3 ml hexachloroplatinic( IV) acid solution (10%) in 97 ml water
and 100 ml 6% aqueous potassium iodide solution
Iron(III) chloride / potassium hexacyanoferrate / sodium arsenate (according to Patterson and Clements) for detection of iodine compounds, e.g. thyroid gland hormones
Solutions:
1. 2.7% iron(III) chloride hexahydrate in 2 N hydrochloric acid
2. 3.5% potassium hexacyanoferrate in water
3. dissolve 3.8 g arsenic trioxide in 25 ml 2 N sodium hydroxide solution heating slightly, cool to 5 °C
and add 50 ml 2 N sulphuric acid, fill up to 100 ml with water
Procedure:
– immediately before use mix 5 ml solution 1, 5 ml solution 2 and 1 ml solution 3; spray onto the dry layer
– dry carefully (temperature below 50 °C)
– cover with glass plate and leave 15 minutes in the dark
Lead tetraacetate/2,7-dichlorofluorescein for detection of vicinal diols, glycosides and phenols, e.g. sugar acids
Solutions:
1. 2% (w/v) lead tetraacetate in glacial acetic acid
2. 1% (w/v) 2,7-dichlorofluorescein in ethanol
Mix 5 ml each of solution 1 and 2 and fill up to 200 ml with dry benzene or toluene. This reagent solution is stable for only about 2 hours.
Manganese/salicylaldehyde for detection of organothiophosphorus pesticides
Solutions:
1. dissolve 100 mg manganese chloride (MnCl2 · 4 H2O) in 100 ml 80% ethanol
2. dissolve 1.3 g 2-hydrazine quinoline in the lowest possible volume
of hot ethanol.
Dissolve 1 g salicylaldehyde in 5 ml ethanol and add 1
– 2 drops glacial acetic acid. Combine both solutions and reflux 30
min. The crystals of salicyl-2-aldehyde 2-quinolylhydrazone
precipitated during cooling are recrystallised from ethanol. For
solution 2 dissolve 50 mg of the salicyl derivative in 100 ml ethanol.
Procedure:
– spray with a mixture of equal volumes of solutions 1 and 2
Mandelin's reagent see under Vanadium(V)/sulphuric acid reagent
Mercury(II) chloride/dithizone for detection of barbiturates
– spray with a freshly prepared 1:1 mixture of 1 – 2% mercury( II) chloride in ethanol and 0.1 – 0.2% dithizone in
ethanol
– view under UV light at 360 nm
4-Methoxybenzaldehyde/sulphuric acid/ethanol for detection of erythromycin and metabolites
– spray with 4-methoxybenzaldehyde/sulphuric acid/ethanol (1:1:9, v/v/v)
– heat 1 min to 110 °C
Methyl yellow for detection of chlorinated insecticides and antimicrobial compounds
Solution:
dissolve 0.1 g methyl yellow N,N-dimethyl-4-phenylazo-aniline) in 70 ml
ethanol, add 25 ml water
and fill up to 100 ml with ethanol
Procedure:
– spray with reagent solution
– dry at ambient temperature
– irradiate 5 min with UV light (without filter)
Molybdatophosphoric acid for detection of reducing substances, e.g. alcohols, bile acids, lipids, fatty acids, steroids
– spray with a solution of 250 mg molybdatophosphoric acid in 50 ml ethanol
– heat to 120 °C until spots appear (heatgun)
– if necessary treat with ammonia vapour
The reagent solution is stable for only about 10 days even in the dark.
Molybdenum blue reaction according to Dittmer and Lester for detection of phospholipids and phosphoric acid derivatives
Solutions:
1. boil 40.11 g MoO3 in 1 l 25 N sulphuric acid for 3 – 4 hours until the molybdenum oxide is completely dissolved.
Let the light yellow solution slowly cool to ambient temperature over night, the solution will turn light blue.
2. boil 1.78 g molybdenum powder and 500 ml of solution 1 for 15 min, cool and decant from the remaining residue.
For preparation of the spray reagent add equal volumes of solutions 1 and 2 to 4.5 volume parts water. A dark green
solution is formed.
Solutions 1 and 2 are stable for several months when stored in the
dark, the spray reagent has to be prepared about weekly.
Ninhydrin for detection of amino acids, amines, aminosugars
– spray with a solution of 0.2 g ninhydrin in 100 ml ethanol
– heat to 110°C until reddish spots appear
Ninhydrin/cadmium acetate for detection of amino acids, and heterocyclic amines
– dissolve 1 g ninhydrin and 2.5 g cadmium acetate in 10 ml glacial acetic acid and fill up to 500 ml with ethanol
– spray and heat 20 minutes to 120 °C
Ninhydrin/pyridine/glacial acetic acid for detection of peptides
– spray with 1% ninhydrin in pyridine / glacial acetic acid (5:1, v/v)
– heat 5 minutes to 100 °C
Nitric acid/ethanol for detection of amines, and alkaloids
– spray with a solution of 50 drops 65% nitric acid in 100 ml ethanol (higher acid concentrations are also possible)
– if necessary heat to 120 °C for some time
Patterson and Clements see under Iron(III) chloride/potassium hexacyanoferrate/sodium arsenate
Phenylhydrazine sulphonate for detection of some antimicrobial compounds
Solutions:
1. dissolve 3.5 g phenylhydrazine 4-sulphonic acid hemihydrate in 10 ml
water and 20 ml 1 N sodium hydroxide solution
2. mix 30 ml 2 N sodium hydroxide solution with 40 ml acetone
The spray reagents have to be prepared fresh every time.
Procedure:
– wet chromatogram evenly with spray solution 1
– after airdrying the plate shake spray solution 2 and spray
Phosphomolybdic acid see under Molybdatophosphoric acid
Pinacryptol yellow for detection of sweeteners, surfactants
Solution:
Dissolve 100 mg pinacryptol yellow in 100 ml hot water or ethanol
Procedure:
– spray with reagent solution
– view under UV light
Potassium dichromate/sulphuric acid (chromosulphuric acid), universal visualisation reagent for organic compounds (e.g. alcohols, also for bile acids, lipids)
– spray with a solution of 5 g potassium dichromate in 100 ml conc. sulphuric acid
– if necessary heat plate to 150 °C
Potassium permanganate/sulphuric acid, universal reagent for organic compounds, e.g. fatty acid derivatives
– spray with a solution of 1.6% potassium permanganate in conc. sulphuric acid
(Beware of explosions during dissolution!)
– heat plates 15 to 20 minutes to 180 °C
Pyrocatechol violet reagent for detection of organotin compounds
– completely decompose metalorganic compounds by irradiation of the developed plates with UV light
– dip plates in a solution of 1 g pyrocatechol violet in 1000 ml ethanol (99.5%)
Rhodamin B spray reagent for detection of lipids
Procedure:
– dry the developed chromatogram
– spray with rhodamin B spray reagent
In most cases red-violet zones with an intense fluorescence at 365 nm develop on a pink background.
RP phases are less suited, because in this case the environment of the
spots also forms an intense colour. By placing the sprayed
chromatograms into an NH 3 atmosphere the detection sensitivity can be
improved.
Rubeanic acid for detection of heavy metal ions
– spray with a solution of 0.5% rubeanic acid in ethanol
– dry briefly
– spray with 25% ammonia solution or place in a chamber with ammonia vapour
Silver nitrate/hydrogen peroxide for detection of halogenated hydrocarbons
Solution:
Dissolve 0.1 g silver nitrate in 1 ml water, add 10 ml
2-phe-noxyethanol, fill up to 200 ml with acetone and add 1 drop
hydrogen peroxide (30% solution)
Procedure:
– spray plate with reagent solution
– irradiate with unfiltered UV light until optimal contrast is obtained. Luckow [Fresenius Z. Anal. Chem. 294 (1979)
288] uses silver nitrate/phenoxyethanol/acetone without addition of
hydrogen peroxide for detection of the pesticide ioxynil
(3,5-diiodo-4-hydroxybenzonitrile).
Sodium nitroprussiate/potassium hexacyanoferrate(III) for detection of aliphatic nitrogen compounds
Solution:
Mix 1 vol. part each of 10% aqueous sodium hydroxide solution, 10%
sodium nitroprussiate solution and 10% potassium hexacyanoferrate(III)
solution with 3 vol. parts water. Let the solution stand at least 20
min at ambient temperature before use. Stored in a refrigerator, it is
stable for several weaks.
Procedure:
– for use mix the reagent solution with an equal volume of acetone and spray
TCNE reagent (tetracyanoethylene) for detection of aromatic hydrocarbons and heterocycles, aromatic amines and phenols
– spray with a solution of 0.5 – 1 g tetracyanoethylene in dichloromethane or benzene
TNF reagent (trinitrofluorenone) for detection of phenols
– spray with a solution of 2% 2,4,7-trinitrofluorenone in benzene or toluene
o-Tolidine/diazotised for detection of phenols
Solutions:
– tolidine solution: fill up 5 g o-tolidine and 14 ml conc. hydrochloric acid to 100 ml with water
– nitrite solution: 10% aqueous sodium nitrite solution, prepared fresh
– spray solution: mix 20 ml tolidine solution and 20 ml nitrite solution at 0 °C, stirring constantly. The spray solution is stable for about 2 - 3 hours.
After spraying it can take several hours until coloured spots are formed!
Triethanolamine, 20% in isopropanol for enhancement of fluorescence
Vanadium(V)/sulphuric acid reagent for detection of carbohydrates, glycols, reducing carboxylic acids, steroids, antioxidants, vitamins, phenols, aromatic amines
a) Ammonium monovanadate (ammonium metavanadate)/sulphuric acid reagent
– spray with a solution of 1.2 g ammonium monovanadate in 95 ml water + 5 ml conc. sulphuric acid or
– for b-blockers: spray with a saturated solution of ammonium monovanadate in conc. sulphuric acid
b) Vanadium pentoxide/sulphuric acid reagent
– Spray with a solution of 1.82 g vanandium pentoxide in 30 ml 1 M sodium carbonate, sonicate to achieve complete dissolution, after cooling add 46 ml 2.5 M sulphuric acid and fill up to 100 ml with acetonitrile
Vanillin reagent for detection of amines and amino acids
– spray with a solution of 1 g vanillin in 50 ml 2-propanol
– dry 10 minutes at 110 °C
– spray with 1 ml 1 M potassium hydroxide solution, filled up to 100 ml with ethanol
– dry 10 minutes at 110 °C
– view under UV at 365 nm
Vanillin/sulphuric acid reagent for detection of steroids
– spray with a 1% solution of vanillin in conc. sulphuric acid
– heat 5 minutes to 105 °C
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