Purpose of TLC analysis

How to prepare a “TLC plate"
1.5×4 [cm]・To check purity of sample
・To detect FG of sample
・To analyze polarity for purification

Make smallerwith cutter

・To trace reaction progress
・To check stability for storage (2D)

20×20 [cm] TLC plate

0.5 ~ 1 [cm]Draw guideline
with pencil

Points・Do not touch the surface of TLC by bare hands. (treat with glove or tweezers)
・Do not trace notch with cutter if you fail to cut.
・When you cut TLC, do not press cutter strongly on TLC.
・Store TLC at sealed bottle to avoid moisture.

How to analyze by TLC (3-Spot TLC is sufficient for most of cases.)
Disappear the reactant in reaction mixtureex.)・You can obtain some information from TLC.
ex1. If TLC is like above right figure, more loading of the reactant possibly facilitate the reaction.
ex2. SM and reactant are remained, but the reaction stop. → cause : deactivation of catalyst etc…
・Develop TLCs as often as possible, at least when the reaction time is 5 min and 1 h.
・If you cannot speculate polarity of sample, try hexane/EtOAc = 2:1 as eluent.
・If you want to know the analytical information of TLC spot,
1. scratch the TLC spot
2. extract with MeOH or AcOEt
3. filter off silica gel
4. analyze by MS, LC-MS or GC-MS
・Filter paper in developing chamber makes the development faster.
・CS2 may improve the solubility of compound (especially suitable for large p-conjugated system).

How to detect TLC spot
1st : UV (254 nm)
2nd : Iodine (I2 – SiO2)
3rd : stains

UV active = black (no FL)
Background = green
I2 active = brown
Background = white(Depends on each method, also see “TLC発色試薬の調製法” by K. Oisaki)How to choose stains
Stain name

Target compound

Treatmentiodine

For most of functional groups

Bury into iodine/SiO2p-anisaldehyde

For most of functional groups (Especially, Ar-OH, sugar)

Phosphomolybdic acid

For most of functional groups

KMnO4For [O].(e.g. –CH2=CH2-, R-OH, -NH2, -SH, etc.)

ninhydrin

For amine, amino acid

2,4-dinitrophenylhydrazine

For only aldehyde, ketone

Ceric ammonium molybdate

For most of functional groups

vanilin

For alcohol, phenol

Dip in stain → heat2D TLC analysis

decomp.

spot
Other TIPS

1st development

Dry & Rotate 90o

2nd development

1) “Hexane - Et3N or pyridine (1% v/v) soaked then dried” normal TLC is also effective to analyze basic sample.
2) Toluene is sometimes effective to affect Rf value of aromatic compound (due to π-π interaction).
3) HFIP and TFE is sometimes effective to separate peptide and carboxylic acid. (due to break hydrogen bond)4) Considering “additive” in solvents (e.g. ~1% EtOH in CHCl3)5) Only UV detection and “イイモリ”(improved Phosphomolybdic acid) are available to analyze NH2-TLC.

How to select TLC type
Normal TLC : Nonpolar sample(standard)
C18-TLC : Polar sample
Neutralized TLC : H+-sensitive sample
Al2O3, NH2-TLC : Basic sample
NH2-TLC: Reaction monitor is often easier
because excess reagents or SM (containing -CHO,COOH, -COCl, and acidic FG) can be trapped atthe baseline.
ex.) -OH →-OTs: trap TsCl
amide formation (with HOBt): trap HOBt

How to select solvent
1st choice: Hexane/AcOEt system(for high polar compound: + MeOH ~10%)(solvent for C18-TLC : H2O/MeOH or MeCN)
If possible, you should not use CH2Cl2 and CHCl3
because of problematic environmental burden.

How to select additive (for normal TLC)
Acidic sample : + AcOH (1% v/v)
Basic sample : + Et3N or Pyridine (1% v/v)

Relative polarity ofordinary solvents*←nonpolar

Polar→*石川正幸、原昭二、古谷力、中沢泰男編 ”薄層クロマトグラフィー” 南山堂 (1972)
R. Neher “Steroid Chromatography” p.249, Elsevier, Amsterdam (1964)

Cost of TLCs
Merck (20 cm x 20 cm)

catalog #Silica gel TLC (0.5 mm)
Silica gel TLC (1 mm)
C18-TLCbasic Al2O3 -TLC
NH2-TLC

1.05715.0001
1.13895.0001
1.15389.0001
1.05550.0001
1.05533.0001¥14,400/box (25 sheets)¥34,800/box (15 sheets)¥57,760/box (25 sheets)¥35,500/box (100 sheets)¥48,200/box (20 sheets)

TLC plate cutter (KN3315765): ¥46,550
Diamond blade (KN3315766): ¥6,460

TLC developing tank
30cm x 30cm : ¥43,000 (Sansyo)
10cm x 10cm : ¥12,100 (Yazawa)

Price (on catalog)

Cost of Accessories