[NHCOLL-L:324] Re: pH meters & electrodes and dermistids & oily fish

[Robert Waller]

Robin
Alcohol/water solutions are problematic for pH measurement because they:
1) tend to clog the liquid junction
2) dehydrate the pH sensitive glass membrane
3) foul the glass membrane with oils and other precipitates.
We have found that the Hach pH electrodes with the dispensing electrolyte
feature eliminate problem #1 and give rapid reliable responses in most
alcohol/water solutions.  They will also work well in formalin solutions.
Their pH meters are constructed for field use, hence they hold up well
around the lab.  Information can be found at:
http://www.hach.com/Spec/ssensio1.htm

They are represented in New Zealand by:
     Biolab Scientific Ltd.
     244 Bush Road
     Albany, Auckland
     Telephone: (64)(9) 980 6700
     National Freephone: 0800 933 966
     Fax: (64)(9) 980 6788

Can't help with the fish recipes though,
Rob

Robert Waller
Chief, Conservation
Canadian Museum of Nature
Box 3443, Station D
Ottawa, Ontario
K1P 6P4
CANADA

phone:(613)566-4797
fax:     (613)364-4022
email: rwaller at mus-nature.ca 
WEB: www.nature.ca

>>> Robin McPhee <RobinM at TEPAPA.GOVT.NZ> 99-11-11 9:27:44 pm >>>
Hi all,
We are looking at getting a pH meter for testing the formaldehyde,
isopropanol & ethanol solutions we use for fixing and preserving fish
specimens.  We don't wish to spend heaps of cash and would like something
portable and reasonably robust.
Can anyone recommend a brand/model of pH meter & electrode that they have
found to be reliable and robust enough for testing solutions of fixative or
preservative and the associated biological "bits" from the specimens?

Also I currently am putting some perciform fish skeletons through our
dermistid colony.  The aim is to produce some reasonably articulated
skeletons, by drying the fish frames (to harden the cartilage, etc.) before
putting them in with the dermistids.  
On some species of fish this technique works well, but on other species it
does not.  
Some species are quite oily, so the remaining flesh on the frame becomes
like sticky toffee, which the dermistid won't eat.  
I've tried soaking the frame in full strength ethanol to remove the oils
with some success, but after the ethanol has been evaporated off the
dermestids still find the flesh unpalatable.
I was thinking of spraying the frames with a beef stock mixture to try and
encourage the little blighters, I suppose as they have previously been feed
on birds skeletons I should try chicken first :-).
Has anybody else had problems getting dermistids to clean up fish skeletons
or found solutions/techniques to make fish skeletons appetising to
dermistids??

Cheers and have a good weekend
Robin McPhee

Technical Officer, EEZ Fishes Project
Museum of New Zealand, Te Papa
P.O. Box 467
Wellington
New Zealand
Phone DDI 64-4-381 7308
Fax 	  64-4-381 7310
e-mail robinm at tepapa.govt.nz