Nigel Baldwin | PIC Pen ink chromatography C0027 @nigelbaldwin3184 | Uploaded February 2021 | Updated October 2024, 5 minutes ago.
Greenhouse chemistry
Fun chemistry experiments in the greenhouse under lockdown
Four felt-tip pen inks were used in a paper chromatography experiment.
The colours selected were yellow, light green, light blue and dark green.
Coffee filter paper was cut into a rectangular shape for the chromatogram.
A glass sugar cube container was used as the chromatography tank, although any suitable piece of glassware would do, such as an empty jam jar.
Nail polish remover was used as the solvent. The label on the bottle said that the nail polish remover was 80% acetone, the remainder being predominantly water.
A horizontal baseline was drawn in pencil, approximately 1cm from the bottom of the paper.
It is important not to put too much solvent into the bottom of the chromatography tank, ie the solvent level must be below the level of the baseline. If this is not the case, then the samples would simply wash off the paper into the solvent as soon as the chromatogram was placed in the tank.
Small spots of each of the pen inks were dotted onto the baseline. It is important not to overload the sample size, although this will need to be determined by trial and error, probably over a series of experiments.
Similarly, a series of experiments will need to be carried out for different kinds of samples to find an appropriate solvent system that gives a good separation of the components in the mixture under analysis.
In this experiment, we wanted to determine if a combination of inks was used by the manufacturer in making the light green ink, or if the light green ink was a single pure colour.
The chromatography experiment was run in a few minutes. This means that it took a few minutes for the solvent to rise up the paper until it reached a level about 1 to 2cm from the top of the paper.
It is important that the chromatogram is lowered into the solvent in one smooth movement and that the chromatography tank is not moved once the experiment has started.
It is also important that the solvent rises up the paper in an even horizontal line of elution. if the paper slants or touches the sides of the glass, it is almost inevitable that the solvent will rise unevenly due to surface tension effects etc.
We have found in previous experiments that coffee filter paper is not strong enough to stand upright, once it becomes saturated with rising solvent and will often flop down, spoiling the experiment.
There are various ways of preventing this from happening and the method of propping up the paper with a bent wooden splint shown in the movie clip is not ideal, but it is quick and tends to have the desired effect. However, other methods may prove superior.
The movie clip was shot in bright morning sunlight and thus the results seen on camera were not as clear as those seen with the naked eye during filming.
Results
Yellow = a single coloured spot with a low Rf value.
Light blue = a single coloured spot with a higher Rf value.
The Rf values were not measured, but these statements simply mean that single spots were seen for the yellow and light blue pen inks and that the light blue ran further up the paper than the yellow ink.
Light green = two coloured spots, corresponding in shape and position on the paper as the yellow and light blue pen inks. Thus, light green ink is likely a mixture of yellow and light blue inks. This would make sense for low cost manufacturing.
Dark green = yellow, light blue and pink.
The pink spot ran very high on the chromatogram at the solvent front and is not very easy to see on the movie clip.
Nevertheless, paper chromatography of felt-tip pen inks proved far easier to carry out than a similar experiment carried out on food colours of natural origin.
Once the chromatogram has completely dried off the distance the spots have moved from the baseline can be measured and the Rf values calculated.
Rf value = distance moved by spot from the baseline / distance moved by the solvent up the paper, as measured from the baseline.
All Rf values will therefore fall in a range of between 0 and 1.
0 = no movement of the spot from the baseline
1 = the spot was at the solvent front and ran as high as the line of solvent reached on the chromatogram.
Paper chromatography questions often appear in GCSE level chemistry examination papers. Paper chromatography also serves as a simple practical introduction to chromatographic separation techniques.
Fun chemistry experiments at home in the greenhouse under lockdown.
Greenhouse chemistry
Fun chemistry experiments in the greenhouse under lockdown
Four felt-tip pen inks were used in a paper chromatography experiment.
The colours selected were yellow, light green, light blue and dark green.
Coffee filter paper was cut into a rectangular shape for the chromatogram.
A glass sugar cube container was used as the chromatography tank, although any suitable piece of glassware would do, such as an empty jam jar.
Nail polish remover was used as the solvent. The label on the bottle said that the nail polish remover was 80% acetone, the remainder being predominantly water.
A horizontal baseline was drawn in pencil, approximately 1cm from the bottom of the paper.
It is important not to put too much solvent into the bottom of the chromatography tank, ie the solvent level must be below the level of the baseline. If this is not the case, then the samples would simply wash off the paper into the solvent as soon as the chromatogram was placed in the tank.
Small spots of each of the pen inks were dotted onto the baseline. It is important not to overload the sample size, although this will need to be determined by trial and error, probably over a series of experiments.
Similarly, a series of experiments will need to be carried out for different kinds of samples to find an appropriate solvent system that gives a good separation of the components in the mixture under analysis.
In this experiment, we wanted to determine if a combination of inks was used by the manufacturer in making the light green ink, or if the light green ink was a single pure colour.
The chromatography experiment was run in a few minutes. This means that it took a few minutes for the solvent to rise up the paper until it reached a level about 1 to 2cm from the top of the paper.
It is important that the chromatogram is lowered into the solvent in one smooth movement and that the chromatography tank is not moved once the experiment has started.
It is also important that the solvent rises up the paper in an even horizontal line of elution. if the paper slants or touches the sides of the glass, it is almost inevitable that the solvent will rise unevenly due to surface tension effects etc.
We have found in previous experiments that coffee filter paper is not strong enough to stand upright, once it becomes saturated with rising solvent and will often flop down, spoiling the experiment.
There are various ways of preventing this from happening and the method of propping up the paper with a bent wooden splint shown in the movie clip is not ideal, but it is quick and tends to have the desired effect. However, other methods may prove superior.
The movie clip was shot in bright morning sunlight and thus the results seen on camera were not as clear as those seen with the naked eye during filming.
Results
Yellow = a single coloured spot with a low Rf value.
Light blue = a single coloured spot with a higher Rf value.
The Rf values were not measured, but these statements simply mean that single spots were seen for the yellow and light blue pen inks and that the light blue ran further up the paper than the yellow ink.
Light green = two coloured spots, corresponding in shape and position on the paper as the yellow and light blue pen inks. Thus, light green ink is likely a mixture of yellow and light blue inks. This would make sense for low cost manufacturing.
Dark green = yellow, light blue and pink.
The pink spot ran very high on the chromatogram at the solvent front and is not very easy to see on the movie clip.
Nevertheless, paper chromatography of felt-tip pen inks proved far easier to carry out than a similar experiment carried out on food colours of natural origin.
Once the chromatogram has completely dried off the distance the spots have moved from the baseline can be measured and the Rf values calculated.
Rf value = distance moved by spot from the baseline / distance moved by the solvent up the paper, as measured from the baseline.
All Rf values will therefore fall in a range of between 0 and 1.
0 = no movement of the spot from the baseline
1 = the spot was at the solvent front and ran as high as the line of solvent reached on the chromatogram.
Paper chromatography questions often appear in GCSE level chemistry examination papers. Paper chromatography also serves as a simple practical introduction to chromatographic separation techniques.
Fun chemistry experiments at home in the greenhouse under lockdown.
