krfkeith - 27-4-2014 at 12:28
There is a procedure I found of interest, which utilizes pyranine dye: http://www.nature.com/pj/journal/v37/n8/abs/pj200576a.html (not sure why they refer to it as "pyranine conk" though). Anyway, it is my
understanding that pyranine is the dye used in yellow highlighters. I have found a few sort of vague references to this in various places online. I
thought the dye was fluorescein? Anyhow, regardless. . .if it is indeed pyranine, what would be a good way to go about trying to purify it?
Texium - 27-4-2014 at 13:16
I also thought that fluorescein was used in yellow highlighters. Maybe different brands use different dyes? I'm not so sure that the Wikipedia page is
right.
I've done the fluorescein extraction, and I successfully boiled down the dye from several Accent highlighters to get a dark red paste, which looks
like what fluorescein is supposed to look like. I'm not sure what pyranine looks like when boiled down, so I won't rule it out, but it seems that
fluorescein is more commonly used, as there are more than "a few vague references" supporting it.
Chemosynthesis - 27-4-2014 at 13:50
Looks like pyranine in Pilot, among others. You can also order it.
http://pilotpen.us/categories/highlighters/
http://colorants.lanxess.com/en/products-applications-cl/pro...
You can also get pyragreen, apparently.
http://www.pyranine.com/in-english-19700869
krfkeith - 27-4-2014 at 13:54
Yes I believe sadly that you are right. I might try emailing the manufacturers claiming this. It isn't mentioned as being in highlighters on the NIH's
household product chemicals website: http://householdproducts.nlm.nih.gov/cgi-bin/household/brand...
However, based on the name D&C Green 8, I may have found a source: http://www.fromnaturewithlove.com/soap/product.asp?product_i...
However, that being said, that same NIH site doesn't mention fluorescein either. In any case, it might not be really worth it.
ScienceHideout - 27-4-2014 at 17:31
Perhaps chromatography? First, test it with paper chromatography. Put a dot on paper, run it, see if one or two dots are formed. Do experiments with
different eluents to see what sort of polarity gives the best separation... Afterwards, dip it in acids and bases to see which one is fluorescein and
which is pyrinine (fluorescein changes colors depending on pH!). Then, make a big chromatography column and run it!!!
krfkeith - 27-4-2014 at 21:10
ScienceHideout: Great idea! I actually did that per your advice.
Here's what I've been able to glean:
It seems there are at least two different dyes used. Fluorescein is undoubtedly used in some, because as mnnemtioned above, there are plenty of videos
of people extracting the brick red paste of fluorescein. Nevertheless, fluorescein is water insoluble (I think?), but the other seems to be. Also, we
have in the case of pilot a direct statement supporting this. The pattern I believe I have noticed, is that the fluorescein highlighters seem to be a
much more golden kind of color, whereas the other seems to look more like an electric sort of yellow. Unfortunately, I have no idea what pyranine
powder looks like. Intuitively, it does make sense that fluorescein would be a darker yellow under normal light, however both seem to form green
solutions, so this is going to be rather difficult.
ScienceHideout - 28-4-2014 at 15:53
Fluorescein is water insoluble, but note that when we say fluorescein, we are usually talking about the water soluble sodium salt of fluorescein.