[b]1.[/b]Is TLC a qualitative or quantitative analysis? Is there any way that it can be both? Explain.
~I say it can be both since it can be used to go and determine what exactly is in a sample of mixed compounds which would be qualitative analysis.
It can also be quantitative since it can be used to monitor a reaction and thus you can see about how much is produced since the substance you are testing with can later be tested (compound still in container after reaction) and the purity and ammount of substance can be determined from it.
I don't know if the 2nd part is correct since I don't know if they are only refering to the TLC plates themselves or it can also refer to the compound in the container that can be tested since the TLC plates themselves cannot determine how much sample there is since it only determines what is in the sample. I also don't know if monitoring of the progress of a reaction is considered quantitative.
[b]2.[/b] Name 5 things that may occur to cause poor results in TLC analysis.
~not sure but...
1.) If the spot is too large the different samples would mix and they would not be distinguishable from each other during UV analysis and would create 1 spotty smudge.
solution- to place moderately sized spotted samples with the samples being spaced properly apart so that they don't mix during the analysis
2.) The solvent goes to the top of the plate which would cause the samples to mix since they wouldn't travel anymore since the plate is saturated.
solution: take the TLC plate out when the solvent is 1-2cm from top of plate.
3.) During the monitoring of a reaction and spotting the TLC plate if the timing when the sample must be taken is off, there could be more than the actual ammount of product in that spotting sample.
solution: keep track of the time when spotting is to be done carefully
4.)Allowing the filter paper to touch the side of the TLC plate. This leads to problems since the solvent on the filter paper would come into contact with the TLC plate causing the solvent to get the plate to get moistened above the sample thus when the sample being moved from the bottom of the plate up gets into contact with that spot of moisture it would be less effective in moving the sample above that spot since it is moist already.
(I have no idea if that is correct above)
solution: don't allow the filterpaper with solvent to come into contact with the sides of the TLC plate
5.)If you allow the plate to dry considerably before you go and draw the solvent from that could lead to a larger than actual Rf value.
solution: quickly go and draw the line of the solvent front before the actual solvent front disappears from drying.
Is this and the above correct?
Thanks alot =)
wait..isn't bolding [b]?? I thought it was..why didn't it work??
did I type something wrong??
1. TLC (Thin Layer Chromatography) can be both qualitative and quantitative analysis. Let me explain why.
Qualitative analysis refers to determining the presence or absence of a particular substance in a sample. TLC can be used for qualitative analysis by separating out the compounds in a mixture and comparing them to known standards or reference compounds. This allows you to identify the components present in the sample.
On the other hand, quantitative analysis refers to determining the amount or concentration of a specific substance in a sample. While TLC itself is not primarily used for quantitative analysis, it can be combined with other techniques to achieve quantitative results. For example, TLC can be used to monitor the progress of a reaction by taking samples at various time points and analyzing the spots on the TLC plate. By comparing the spot intensities or calculating the spot areas, you can estimate the relative amount of the compound in the sample and determine its concentration.
Regarding your concern about determining the amount of sample based on TLC plates, you are correct that TLC plates themselves cannot directly measure the quantity of a compound. The quantitative aspect comes into play when you extract the compound from the TLC plate and analyze it using a separate technique, such as spectroscopy or titration, to determine the amount or concentration.
2. You have listed some common issues that can result in poor results in TLC analysis. Let's discuss them, and I will provide some solutions:
1) Large spots: If the spots are too large, they can overlap, making it difficult to distinguish different components during UV analysis. The solution is to use smaller and more concentrated spots, ensuring they are properly spaced on the TLC plate.
2) Solvent front reaching the top of the plate: If the solvent front reaches the top of the plate, the samples will not travel any further, causing mixing and poor separation. To avoid this, remove the TLC plate from the solvent when the solvent front is about 1-2 cm from the top.
3) Incorrect timing for sample spotting: If the timing for spotting the TLC plate during reaction monitoring is off, you may end up with more or less product than the actual amount. The solution is to carefully track the reaction time and spot the plate at the specified intervals.
4) Filter paper touching the TLC plate: When the filter paper comes into contact with the side of the TLC plate, the solvent from the paper can wet the plate above the sample spots, affecting the movement of compounds. To prevent this, ensure that the filter paper with the solvent does not touch the sides of the TLC plate.
5) Allowing the plate to dry considerably before drawing the solvent front line: If the plate dries too much before marking the solvent front line, it can lead to inaccurate Rf (retention factor) values. To avoid this, quickly mark the solvent front line before the actual solvent front disappears due to drying.
Your explanations and solutions for these issues are generally correct. By addressing these potential problems, you can improve the reliability and accuracy of your TLC analysis.
I hope this helps clarify your questions! If you have any further queries, feel free to ask.