What does streaking on a TLC plate mean?
If the TLC plate runs samples which are too concentrated, the spots will be streaked and/or run together. If this happens, you will have to start over with a more dilute sample to spot and run on a TLC plate.
What causes streaking on TLC plates?
In the absense of overloading the plate, some pure compounds can streak on the plate, due to posessing strongly acidic or basic groups, which cling to the active sites of the adsorbant.
What are the spots on a TLC plate?
The silica gel on the TLC plate is impregnated with a fluorescent material that glows under ultraviolet (UV) light. A spot will interfere with the fluorescence and appear as a dark spot on a glowing background. While under the UV light, the spots can be outlined with a pencil to mark their locations.
What problem could streaking spots lead to?
Then lightly touch it to the TLC plate to apply a spot of sample onto the spotting line (1 cm line). What problem could streaking spots lead to? When it is not balanced and it goes up crooked how do you know results are accurate?
What causes Tailing in TLC?
Tailing in TLC; is due to the incorrect solvent system moving phase. Some of the compounds such as amine gives tailing. You can solve it by adding a few drops of triethylamine in the solvent mixture. Tailing or a broad spot is seen when the solvent phase system is not appropriate for the product formed.
What happens if the spots are made too large when preparing a TLC plate for development?
What will happen if your spot is too large? If the spot is large, then two or more spots of a sample may overlap on the TLC plate, thus causing erroneous conclusions about the separation and/or the sample’s purity or content.
Why does TLC have tailing?
What is the adsorbent in TLC?
The silica gel remains the most important adsorbent for TLC separation. The kinetic properties of the silica gel thin-layer and the new TLC plates have been presented. Other materials used as stationary phase were alumina, zirconium oxide, Florisil, and ion-exchanger.
What does multiple spots on a TLC plate mean?
Ideally, each compound in a mixture will produce a distinct spot so a sample with two compounds will give two different spots, and so on. An important property of any compound, is its Rf-value (retention factor). In simple terms, this value is an indication of how far up a TLC-plate a compound has wandered.
How are the spots on TLC plates observed?
What solvent is best for TLC?
Solvent Systems for Thin Layer Chromatography
- Polar compounds: 100% EtOAc or 5% MeOH/dichloromethane.
- Normal compounds: 10-50% EtOAc/Hexane.
- Nonpolar compounds: 5% EtOAc/hexane, 5% ether/hexane, 100% hexane.
What two other factors can cause the developed spots to appear as a streak?
Developed spots can appear as a streak if there are too many components in the sample. Some solvents can cause pure compounds to streak.
How to solve the tailing problem in TLC plate?
Compounds which is basic in nature are often tailing on silica coated TLC plate because silica is acidic in nature so they interact with one another and doing tailing. For overcome this problem, add a little triethylamine in mobile phase to solve this problem. Different ratio of triethylamine can resolve this issue.
Why do I see a long streak on my plate?
If your sample contains a complex mixture of products, then you may see them as a long streak on the plate, and you may need to consider different solvent systems and lower loading to see if you can resolve the different components.
Why does my TLC plate show Double spotting?
If double spotting is observed, this is often due to applying the sample to the baseline in a polar solvent, which gives a ring on the baseline, rather than a tight spot. Can you determine what is the problem in each of the TLC plates sketched above?
What is the size of TLC plate?
The size of TLC plate may be 2.5×5 or 2.5×7.5 0r 3×10 cm. we can use size of TLC plate according to our requirement and number of samples spots. There is some thumb rule for find constituents in mixture for TLC analysis.