Chromatography. SCUHS General Chemistry for Allied Health Lab 4 10/22/2016. Minji Lee. Partner: Ambar Hickman

Transcription

1 Chromatography SCUHS General Chemistry for Allied Health Lab 4 10/22/2016 Minji Lee Partner: Ambar Hickman 1

2 Introduction Chromatography is defined as the separation of a mixture by passing it in solution or suspension or as a vapor (as in gas chromatography) through a medium in which the components move at different rates. It is a method to look at complex mixtures by separating them into their original components. There are two main types of chromatography: gas chromatography and liquid chromatography. Different types of fluids and inks have different components and properties and can determine the solution s solubility and polarity. After placing the chromatography paper into the solvent, the solvent beings to rise up the paper. As the solvent rises, whatever ink or fluids that used on the paper will dissolve, separate, or have no effect on the components and as farther the ink travels along the paper, scientists can approximate the attraction to the solvent. This process was developed between the 1940 s 1950 s in order to determine the separation of molecules in a medium. Criminal investigators and forensics would use this technique to identify substances such as blood, ink, drugs, and other possible fluids. Experiment Since different types of ink has different properties, chromatography papers are used during liquid chromatography experiments. In this case, the following instruments and solutions were involved to perform the experiment in the following table: Materials Chromatography Sheets Quantity 2 (1 cut into ½) = 4 ( ½ sheets) Sharpie (blue) 1 Food Coloring (blue, red, green) 3 2

3 50mL beaker 2 H2O Methanol Approximately 15 ml Approximately 15 ml Capillary tubes 3 Two 50mL beakers were filled, one with about 15mL of H2O and the other with about 15mL of methanol. A horizontal line was drawn using a blue sharpie marker towards the bottom of two half chromatography sheets and were gently placed into the solutions made up of water and methanol in the other. The sheets were barely touching the top of the solutions so that the ink wouldn t bleed into the solutions. During the second trial, tiny drops of food coloring were placed on each of the half chromatography sheets and also gently placed into the solutions. Data/Results The solutions visibly made its way up the sheets, one being water and the other being methanol. As we watched the solutions rose towards the top, it finally made contact with the line drawn by the blue sharpie ink and the results were very interesting. The chromatography paper placed inside the water beaker did not have any change or differences. Meaning, the horizontal line on the paper, remained the same and maintained its original state. On the other hand, the chromatography paper placed inside the methanol, as the solution rose up the sheet, the ink molecules followed and also rose up the chromatography paper (pictures are shown below). 3

4 (Chromatography paper placed in methanol solution on left, paper placed in water on right) As you can see above, inside the water, there are no changes and the sheet placed inside methanol, there is a distribution of molecules with light blue color towards the bottom, and a stronger molecule gathering towards the top. Another trial was done but this time using different type of ink. We used food coloring with the colors of red, blue and green. Using capillary tubes, one micro drops of each of the colors were placed on the chromatography paper. During the second trial, it was very fascinating to see the different results that were portrayed compared to the first one. Although we used both of the same solvents, the ink that were placed on the chromatography sheets had a different trend compared to the first one. In the 1 st trial, the molecules of the blue sharpie followed the methanol as it rose up the paper and the origin of the line faded away. In the 2 nd trial, the sheet of food coloring placed in water had the same effect as the 1 st trial s methanol; the origin of the drops faded away as the color molecules rose up the paper along with the water. As for the sheet of 4

5 food coloring that was placed in the methanol, the ink also rose up as the methanol soaked the paper, but the initial starting point almost remained the same as the top and had a streaking effect (photos are shown below). (Chromatography paper with droplets of food coloring placed in methanol on left, paper placed in water on the right.) Conclusion As you can see here, there is an obvious segregation of yellow and blue where the droplets of green were placed. This satisfyingly reveals the true purpose of the chromatography test, which is to find the original pieces that make up a component. In addition, chromatography also shows the polarity or solubility of any type of material, in this case a liquid substance. As 5

6 the photos show above, the only non-polar component in this experiment resulted in being the blue sharpie ink mixed with water. This can be concluded due to the water having no effect or making no changes in the ink molecules drawn on the chromatography paper. The rest of the 3 trials (blue sharpie ink in methanol, droplets of food coloring in methanol and water) all appeared to have a polar or soluble effect amongst the interactions between the ink molecules and the solvents. 6