On Fri, 4 Dec 1998, Mick Rentsch wrote:

> Can anyone suggest what concentration Glyoxal should be used at as a
> substitute for 10%NBF, and is it better with Saline or buffered to pH
> 6.8-7.2.
> The Merck Index suggests that dissolving the Glyoxal presents special
> hazards, does anyone have any experience?

  According to the Sigma catalogue, glyoxal is available commercially
  only as its hydrated trimer (formed when glyoxal reacts with itself
  and water). They sell this as solid ($17.90 for 100 g) and as a
  40% aqueous solution ($24.80 for 100 g).

  Pearse's Histochemistry (4th ed, Vol 1, p. 104) mentions it
  rather briefly, giving a reference to Nakaya et al 1969 Biochim
  Biophys Acta 194:301. On p. 60 Pearse includes glyoxal in a
  list of 16 substances he tested as vapour-phase fixatives for
  freeze-dried objects. He didn't comment on its efficacy.

  It would seem reasonable to dilute the glyoxal trimer with
  an isotonic sodium phosphate buffer. I do not know how this
  would compare with the commercially available ready-mixed
  glyoxal-containing fixatives. It ought to be cheaper to
  make your own.

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1