Chromatography

Before:

After:

Our chromatograms:

Above is a photo of my lab partner, Megan, and I with our favorite chromatograms that we made together. Below, I answer a few questions about this colorful lab!


Q & A:

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

The purpose of this lab is for the black ink to spread itself across the filter paper. If the paper is in direct contact with the water, the paper will get saturated quickly. By having the wick in between, the water gradually reaches the paper and the ink slowly spreads.

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

The components of the ink used and the pattern that is initially made with the ink on the filter paper affect the pattern of colors produced.

Why does each ink separate into different pigment bands?

Components of the ink that are not easily adsorbed onto the paper will spend more time in the solution and will move up the paper at a faster rate. Therefore, the different components end up in different bands on the paper based on their color.

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.

Looking at the color blue on both chromatograms, we see that it's on the outer band. The two chromatograms have the same blue pigment. Though the chromatogram on the left (above) looks like it has a more concentrated band of blue, that whole chromatogram itself looks more concentrated. The two pens used to create these pigments appear to contain common pigments, as both chromatograms go from yellow to red to blue respectively from the inner band to the outer band.

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?

Water-soluble markers and pens were used in this activity because water was the substance used to separate the components of the ink. If we used other types of markers or pens, water would not be sufficient to separate the pigments. The experiment could be modified to use a different solution, such as rubbing alcohol (instead of water), to catalyze the pigment separation for permanent markers or pens.