Sub-visible Fluorescent Dye Tracing?

[jarvist]

To an extent this is a continuation of a previous discussion of dye tracing:
http://ukcaving.com/board/index.php?topic=3737

On the practical side, I thought people may be interested to see that there's a 'shop' on eBay offering Fluorescein and Rhodamin-B for around ?5-6 per 100g bag.
http://myworld.ebay.co.uk/home_and_hobby_chems/

However, my question is whether anyone has attempted to go beyond the naked-eyeball direct or fluorescent (i.e. UV lamp) analysis of Charcoal / cotton-wool samples?
Attempted to observe fluorescence with high intensity UV diode lasers / green laser pointers?

I understand that Fluorescien is visible (i.e. water is green) in parts-per-million concentration, and imagine that UV fluorescence with a well shielded UV source might get that threshold down to a couple of ten parts-per-billion, but does anyone know the limits?

There's a company in America that does groundwater dye tracing, using a spectrofluorometer to get to parts-per-trillion level of detection threshold. They describe their laboratory procedure in some detail (see link below), the use of a Ammonia/1-propanol eluent to recover the dye from the dried charcoal sample collector seems like it would be easy enough to do in a caving hut.
http://www.dyetracing.com/?page_id=7
By using a spectrofluoremeter you can see the traces of individual dyes (with different PL optical properties) and quantities, so be able to consider multiple simultaneous dye traces to one set of detectors.

In general, are there any publications on dye tracing / attempts at a quantification of the amount of tracer required, detection limits etc. ?

 

[graham]

Try

Crabtree,R.W., 1979. Quantitative fluorometric dye tracing, Rickford and Langford resurgences, Northern Mendip

Smart,P.L., and Stanton,W.I., 1981. Repeated dye traces of underground streams in the Mendip Hills, Somerset

Hobbs,S.L., and Smart,P.L., 1989. Delineation of the Banwell Spring catchment area and the nature of the spring hydrograph

Edwards,A.J., Hobbs,S.L., and Smart,P.L., 1991. Dye tracing in the Beacon Hill Pericline, East Mendips

All from UBSS Proceedings

 

[jarvist]

Thanks for that Graham, very interesting background reading. The detection thresholds seem fairly high though, perhaps simply a matter of fluorometer technology marching on...

I've also found a cheap source of Lycopodium spores in London:
baldwins.co.uk

They're sold as a 'health food', so will quite possibly be totally fake, but as they're just down the road I'll go and buy a small sample & have a look under a 'scope.
?7.45 for a 100g sample is an order of magnitude cheaper than what I was quoted for a (scientific) sample of pre-dyed spores a few years ago. They should be easy enough to stain at home with Rhodamein-B, perhaps Fluorescein too.

 

[sluka]

However, my question is whether anyone has attempted to go beyond the naked-eyeball direct or fluorescent (i.e. UV lamp) analysis of Charcoal / cotton-wool samples?
Attempted to observe fluorescence with high intensity UV diode lasers / green laser pointers?

From wikipedia: "Fluorescein has an absorption maximum at 494 nm and emission maximum of 521 nm (in water)"  and it is NOT UV!

Blue LEDs for fluorescein detection? -> http://osdir.com/ml/diybio/2011-05/msg00397.html

Martin

 

[graham]

Sorry, yes, half asleep today, Sluka is quite right. UV lamps can be used to detect optical brighteners that have been used in tracing and adsorbed onto cotton wool, not fluorescein.

i don't know about technology marching on, I do know that the geog dept one here used to spent a lot of time being a bit 'not working properly'. I also suspect that there are practical limits far higher than the theoretical limit depending on what else might be in the water.

I also believe there were good reasons why they stopped using Lycopodium spores and went with dyes, but I cannot remember what they were at present.

 

[jarvist]

Sluka, Graham: certainly Photo-luminescent efficiency will be higher at the absorption maxima. However, this isn't great if you're using your eyes as detectors as blue-green light looks pretty similar to green-yellow emission (the Stokes shift is only 20-30nm for a good fluorescent dye...)! It will certainly still fluoresce when whacked with UV, just not as brightly for the same input power, but this doesn't matter as the overall signal-to-noise is massively improved by the fact that you can't see the UV. Of course you may also start seeing natural fluorescence (such as the peat staining mentioned by NigR in the previous discussion) / from contaminates (such as optical brightener in washing powders...).

I happen to have a bright Blue LED which I've been meaning to mod into a dive torch for night time natural fluorescence, in that case you wear a yellow-film visor over your mask to block the majority of the blue scatter. Something similar might work with Fluorescein.
Rhodamin-B should strongly fluoresce when hit with a green laser pointer (532nm), and you should be able to block any green scatter with a standard pair of Blue/Green blocking (red/orange coloured) laser goggles.

I'll get experimenting... have a horrible feeling that my bath might be rather stained shortly...

On a related matter, I've found that quite a good chunk of 'Tracing Techniques for Hydrogeology' can be read on the Google book page:
http://books.google.co.uk/books?id=def-XuIB-t0C&lpg=PR13&ots=HHUx9n92ud&dq=Lycopodium%20K%C3%A4ss&lr&pg=PA187#v=onepage&q=Lycopodium&f=false

Lycopodium spores float, so perhaps there's an issue with their behaviour in sumped sections? I'm also sure it's a lot easier to do quantitative analysis with dyes, rather than by spore counting in a sample.

 

[Rhys]

Lycopodium spores float, so perhaps there's an issue with their behaviour in sumped sections? I'm also sure it's a lot easier to do quantitative analysis with dyes, rather than by spore counting in a sample.

I thought one thing that makes lycopodium spores useable for water tracing is that they're neutrally bouyant and can pass through sumps as if they were water.

Rhys

 

[JohnMCooper]

There is a reference in the Latest Cave and Karst Science (Volume 38 Number 1 Aprill 2011) which mentions Rhodamine. Whilst not mentioning Rhodamin B it says Rhodamine WT was specifically developed for water tracing but recent studies have shown it can be mildly toxic and it is recommended that Amidorhodamine G is used instead. Before buying anything find out the consequences of using it.

 

[graham]

John makes a very good point. There is a further one in that anything that might pollute should be OK'd by the Environment Agency.

 

[NigR]

The major problem we encountered when using lycopodium spores on the Black Mountain was that the nets kept getting broken by flood water. Quite a few tests that should have given good results (i.e. in optimum conditions) were totally negated due to this. Obviously, this could be solved by using a stronger net but there was nothing available at the time.

Also worth bearing in mind, particularly if you are planning on using spores to obtain a timed trace, is that they can 'pond up' and be washed through later on by a secondary pulse. Hence careful analysis of the prevailing weather conditions (and water levels) is essential when attempting to interpret your results. This problem does exist with dye as well but (at least in my experience) it is far more pronounced with spores.

 

[Rhys]

http://www.dyetracing.com/ might be useful. Dunno though, I only scan read a bit.

Rhys