LactoPhenol/LactoGlycerol

[Peter Werner]

D.BRAYFORD at cabi.org ("David Brayford ", IMI) writes:

>Please note that the widely used stain lactophenol blue actually contains 
>phenol, which is a hazardous substance.  You should therefore avoid skin 
>contact or inhalation of vapour if you want to use this stain.  At IMI we 
>have swapped over to using aniline blue in lactic acid, which is not 
>hazardous and works just as well for most purposes.

If you're preparing the solution yourself from powdered stain, then 
lactoglycerol is a preferable alternative to lactophenol; it works just 
as well and is much safer.  To prepare simply combine two parts water, 
two parts glycerol and one part lactic acid (if the lactic acid is highly 
concentrated, it may need to be heated together with the water for a few 
hours to saturate the lactic anhydride portion of the acid).

I do have a question about lactophenol as a preservative; I've cleared 
and stained a large quantity of fine roots (more than I need to make 
slides at the moment) and I want to put them in long-term storage. The 
protocol I have recommends storage in lactoglycerol; this is fine, but 
other people in my lab have had problems with long-term storage in 
glycerol - yeasts and other microorganisms can grow in glycerol and this 
ruins the occasional sample. I'm not sure if the presence of lactic acid 
is sufficient to discourage the growth of these organisms, so for storage
I'd like to use a lactoglycerol solution that also contains a certain 
percentage of lactophenol.  I'm not sure what a sufficient percentage of 
phenol would be to discourage organisms from growing on my stored 
samples; does anyone have any suggestions?

Thanks,
Peter