Lab 2- chromatographic methods post lab questions (updated) PDF

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Tanvi Kulkarni September 20, 2020

Lab 2: Chromatographic methods: Separation of dyes and spinach pigmentation by column and TLC 1. Carboxylic acids are polar and so is the silica gel, so when the two polar molecules come in contact with each other it produces a streaking effect. DMS is another type of acid that is similar to carboxylic acid which can take the place of the real carboxylic acid to minimize the streaking effect.

2. Polarity is something that needs to be taken into consideration when introducing a mixture of compounds. If the polarity starts to change in the middle, the mixture will not be eluted or elute more than needed. The second precaution is to make sure that the stationary phase is property carried out because not having a distinct stationary phase can make the bands irregular.

3. One disadvantage of thin layer chromatography compared to column chromatography is that not as much of the compound can be absorbed by the stationary phase. This is because the stationary phase is layered thinly onto either glass or aluminum, instead than all of it being contained in the stationary phase. Another disadvantage is that thin layer chromatography can only be done on soluble compounds, while column chromatography can be done with multiple states both in the stationary phase and the mobile phases. Lastly, a third disadvantage is that other variables can affect the results produced by thin layer chromatography such as the temperature and humidity of the location. This can make replicating results difficult unless all factors are being controlled for.

4. No it would not be appropriate to use water- dimethylformamide because both water and dimethylformamide are polar and the end product has a very high polarity. The only advantage would be that it would elute the columns much faster but it would not separate properly.

5. The compound can dissolve above the alumina level if we don't allow the liquid to drop below the level of alumina. This can cause the data to be skewed and can also cause the band to be more diluted.

6. Column chromatography only works when the solvents are flowing constantly and the flow of solvents is what keeps those compounds moving down into the column at many different paces. When the flow of the solvents stop, there is a possibility that the solutions will mix with each other and go in different directions....