I am looking for a non-toxic, water-soluable florescent dye
(preferably FDA approved).  I have been told the chicken processing
industry used such a dye several years ago, but has discontinued the
use.

Hi Frankie,

Good day and thanks for your question.

I believe the dye you're looking for is Rhodamine WT. 
Rhodamine WT has been approved as a tracer dye in potable water in the
United States
( Cotruvo, J. A., RHODAMINE WT AND B, Memo to P. J. Traina, dated
April 10, 1980 )

Rhodamine WT is related to rhodamine B, a tracer in common use in the
1960s.  It was developed to overcome a disadvantage of rhodamine B,
absorption on suspended sediment.  The same modification was expected
to reduce toxicity, and limited testing bore this out.

Rhodamine WT was an immediate success as a tracer in marine systems
and in wastewater.  While it was also used in potable water, such use
was occasionally forbidden on the grounds that it did not have formal
Federal approval for such use.  Rhodamine WT is now approved for such
use.  A brief history follows.

While the EPA has sole responsibility for identifying those substances
which may be used a tracers (2), the Food and Drug Administration
(FDA) does issue policy statements.  The FDA did issue such a policy
statement on 22 April 1966 concerning rhodamine B (3).  A temporary
tolerance limit for ingestion of rhodamine B was set at 0.75 mg per
day.  Based on normally expensed water consumption, the tolerance
would not be exceeded unless the concentration approaches 370 parts
per billion (PPB).  Noting that 30 PPB may be detected visually in a
glass of water, and 10 PPB is visible in larger volume such as a clear
reservoir, the FDA pointed out that if the dye is not visible, the
tolerance would not be exceeded.  The USGS, a large user of
fluorescent dye tracers, directed that the concentration should not
exceed 10 PPB at the intake of a water supply (4).  The visual and
instrumental detectability of rhodamine WT, based on active
ingredient, is about the same as rhodamine B (rhodamine WT is supplied
as a 20% aqueous solution).

Ten parts per billion may not sound like much to the uninitiated, but
it is a thousand times the limit of detectability guaranteed by Turner
Designs on its Model 10 Series Fluorometers (5).  Background
fluorescence caused by fluorescent materials in the water being
studied usually limits detectability.  But even so, measurements can
be made to 0.1 part per billion of rhodamine WT (active ingredient),
in raw sewage!

http://ontario.cfe.cornell.edu/biocomweb/rhodamine/sterlingpondstudy.html
for a full detail on Rhodamine

Fact Sheet on Rhodamine
http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc03/icsc0325.pdf

For more reading...
http://smig.usgs.gov/SMIG/rhodamine_reader.html

For commercial product information,

Crompton and Knowles Corporation
http://www.crompton-knowles.com
800-667-4408  

Kingscote Chemicals
http://www.brightdyes.com
937-886-9100  

Keystone Corporation
http://www.dyes.com
800-522-4dye Headquarters
800-447-4dye Pacific 
 
If you have any clarifications, please don't hesitate to ask

Thank you for using this service and have a nice day.

Warm regards,
aditya2k

---

Clarification of Answer by aditya2k-ga on 25 Nov 2002 13:07 PST

Thanks for the nice words and full rating. If this chemical doesn't
match with what you're looking for, then please post a clarification
and I will work on it.

On another note, I don't know if you would be able to tip me once the
question is rated. You could do something like post a $2 question for
me excluisively and tip me on that

Regards,
aditya2k

I was blown-away by the "turn around time" !!!...after we do some
field tests, if this is in fact the correct chemical, I will
definitely tip aditya2k. More later...and thanks for a great job...I
think.

another option is curcumin--it is the dye that gives the spice
turmeric its yellow-orange color and is structurally related to
b-carotene.  I believe it fluoresces at around 520 nm at neutral pH.