Lab 2A: Chromatography Lab

Before:

After:

My partner Meghana and I with our two favorite chromatograms!

Questions:

1)  Why is it important that only the wick and not the filter paper circles be in contact with the water in the cup?

It's important that the filter paper isn't entirely saturated at first so the water can seep through the wick and slowly onto the paper, which then gives the ink time to spread out from the center and separate into the different pigments.

2)  What are some of the variables that will affect the pattern of colors produced on the filter paper?

Some variables include the type of pen used (since different inks are composed of different colors), the pattern drawn using the pens, the distance the pattern was drawn from the center, the amount of ink used, and the length of the wick.

3)  Why does each ink separate into different pigment bands?

Each ink has different mixtures and will travel up the paper at different rates depending on their characteristic physical properties.  Some components in the mixture are more strongly adsorbed onto the paper than others, and those will move up the paper more slowly than the solvent.  Components that are not strongly adsorbed onto the paper will move up the paper more slowly than the solvent.  This "partitioning" of the components of the mixture between the paper and the solvent separates the components and creates different pigment bands.

4)  Choose one color that is present in more than one type of ink.  Is the pigment that gives this color always the same?  Do any of the pens appear to contain common pigments?  Explain.

Blue is one color that is present in both chromatograms, and the pigment that gives this color is always the same, since blue is used in the ink of many types of pens and markers.  Many of the pens appear to contain common pigments besides blue, such as yellow, orange, pink, and a bit of violet.  The order that the colors show up from the circle is also similar on both papers -- yellow, orange, and pink (warmer colors) are near the center, and blue, the cooler color, is on the outer side.

5)  Why are only water-soluble markers or pens used in this activity?  How could the experiment be modified to separate the pigments in "permanent" markers or pens?

Only water-soluble pens were used so that water could cause the ink to spread across the filter paper.  The experiment could be modified to separate the pigments in permanent markers by using a solvent, for example, rubbing alcohol, that is able to "remove" or separate permanent markers.