ludemas19
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Registered: 15-1-2024
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Fluorescent fun with red ink components: lab notes
Good evening!
This morning we came across a peculiar phenomenon: when some red pen marks are washed with hand sanitizer the colour shifts to a bright orange and
exhibits strong fluorescence when shone with a UV light.
A fluorophore is present, so started our quest to extract it.
First thing we did was take out the ink cartridge of the red pen (a Pilot one), pour a single drop in a cup and dissolve it with some amount of
ethanol.
For the sake of reporting, we used the pink, cleaning one, with most likely other junk in. Of course we checked before hand in case it exhibits some
degree of fluorescence but it doesn't.
After a first dilution of the ink we could already observe a color change to orange and the fluorescence.
Then we kept on diluting adding ethanol dropwise, constantly shining the UV light, the dynamics were very very cool: as soon as a drop was added, we
could see yellowish fluorescent streams of liquid dart through the surface, eventually mixing up with the orange-ish background. At last, we ended up
with a not so clear yellow fluorescent orange liquid.
We tried with isopropanol: we poured high amounts of it in the original cup with the first drop of ink and we got a similar orange-ish cloudier
liquid. (We will investigate this further, isopropanol is too a commercial one, with an orange scent as additive)
Then came the second surprise: when cleaning up, we observed a magenta residue that stuck to the cup, that wouldn't go away with water. We poured
ethanol to dilute it (luckily it worked) and we got a magenta solution, a bit stronger in color than plain ethanol.
We shone that too with the UV light and observed some further pink-ish fluorescence, though not as strong.
I'll share the pictures. Going clockwise from top left the two liquids next to each other in normal light vs in UV light. Then the magenta liquid
compared to ethanol in UV light and lastly the orange one.
As for now, we have no way to confirm the identities of the fluorescent compounds. We have some hypothesis based off the colors (and their beign used
in ink production): for the orange one Eosin Y, for the magenta one Rhodamine wt.
Of course, we don't doubt that in this first extraction, the two "fractions" are not well separated. Tomorrow we will try again with isopropanol first
(which apparently leaves the magenta residue) and later ethanol.
Suggestions are more than welcome!
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Keras
International Hazard
Posts: 1013
Registered: 20-8-2018
Location: (48, 2)
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Isn't red ink eosin, i.e. tetrabromofluorescein? That would explain part of it at least.
Wikipedia says eosin was named after a friend of the discoverer, but eos in Ancient Greek also means 'red' as in the colour of dawn.
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