Why do you use a pencil and not a pen to mark TLC plates? Answer: The pen ink becomes mobile on the plate and travels up the TLC plate with TLC solvent. But the solid particles of graphite in the pencil won’t get dissolved and hence can be used to mark TLC plates.
Why must a pencil be used to mark the origin line on the TLC plate more than 1 answer can be correct?
Why must a pencil be used to mark the origin line on the TLC plate? (More than 1 answer can be correct.) Graphite does not dissolve in the eluent and climb the plate. The ink from a pen is composed of organic compounds that will dissolve in the eluent. -Graphite does not dissolve in the eluent and climb the plate.
Question: When marking a TLC plate, you should always use a pencil (not pen) because: Pencils are cheap and readily available in most chemistry labs The pencil mark will help the compounds elute up the plate If a pen were used, the ink would be carried up the TLC plate complicating interpretation of the results The
What might happen if a student used a pen to mark the baseline on the chromatography paper?
What might happen if a student used a pen to mark the baseline on the chromatography paper? The solution will move to the top and you would not be able to calculate the Rf value that is compared to the distance that a component traveled in the stationary phase reached by the solvent.
Paper chromatography method. 1) Draw a line near the bottom of a sheet of filter paper using a pencil because pencil marks are insoluble and won’t dissolve in the solvent. 2) Add a spot of the ink to the line and place the sheet in a beaker of solvent, e.g. water. 3) The solvent used depends on what’s being tested.
What would happen if a pen was used to mark the lines on the TLC plate?
You can’t use a pen because the ink will travel up the TLC plate with the TLC solvent, just like your chemical samples do. You can only spot/label/mark TLC plates using a pencil. The graphite in a pencil will not run up the plate!
What is the importance of Rf value in chromatography?
In thin-layer chromatography, the retention factor (Rf) is used to compare and help identify compounds. The Rf value of a compound is equal to the distance traveled by the compound divided by the distance traveled by the solvent front (both measured from the origin).
Answer Expert Verified
The position of the solvent front is marked in pencil and the chromatogram is allowed to dry and is then sprayed with a solution of ninhydrin. Ninhydrin reacts with amino acids to give coloured compounds, mainly brown or purple.
Why is it important to keep the spots applied to the chromatography paper small?
keeping small spots on your silica plate (or whatever your immobile phase is) will allow for greater resolution between the spots allowing for more accurate Rf calculations and solvent separation/preparation if using to isolate a compound in a mixture.
What is pencil lead made of?
The “lead” in a pencil isn’t actually made from lead. It is made from a form of carbon called graphite. The graphite is mixed with clay and formed into long thin pencil lead.
Why must you use a pencil and not ink or felt tip pen to mark on the paper the origin of the spots of the amino acid preparations?
1 Expert Answer
Ink will “run” up the paper along with the solvent and make a mess. The graphite from the pencil is stabile and will stay in place.
why is it important that you marked the origin line and component locations on the paper with a pencil and not a pen or marker? A pencil is not ink so it does not separate when placed in the beaker.
Why was it important not to let the ink spot be under the level of the water?
It is important that the solvent level is below the line with the spots on it. As the solvent slowly travels up the paper, the different components of the ink mixtures travel at different rates and the mixtures are separated into different coloured spots.
Why is it necessary use a pencil when writing on a TLC plate quizlet?
You can only spot/label/mark TLC plates using a pencil. The graphite in a pencil will not run up the plate!
Why do you use the narrow end of the capillary tube to spot your sample on the TLC plate?
Capillary spotters, or TLC spotters, are very useful for depositing small amounts of sample onto a TLC (thin layer chromatography) plate. This prevents overloading and helps achieve an accurate and clear TLC in preparation for running a full column. A capillary tube with two open ends will create two TLC spotters.
The most common non-destructive visualization method for TLC plates is ultraviolet (UV) light. If a compound absorbs 254nm UV light, it will appear dark, as the compound prevents the fluorescent material from receiving the UV light.
