1. Measure 100ml Phosphate Buffered Saline (PBS) into a measuring cylinder. Pour into the conical flask containing 4g of paraformaldehyde. Cover with parafilm and transfer to the fume hood: thoroughly shake - take care not to splash paraformaldehyde about - it is a rapid fixer and is TOXIC.

2. Place flask on top of the hotplate/stirrer inside the fume cupboard and set the heat control to 7 with moderate stirring. Allow the solution to warm up-it will turn from being cloudy to clear when ready. Inspect regularly to avoid over- heating and consequent spilling.

3. When the paraformaldehyde has dissolved, switch off the heat but leave to stir: do not handle for safety reasons. Allow to cool.

4. When cooled, transfer the fixative to a 4C refrigerator. Label appropriately and date.

0.4% PARAFORMALDEHYDE/PBS (FOR POST-DIGESTION FIXATION)

This fixative solution should be made up fresh.

Dissolve 0.4g paraformaldehyde/100ml DEPC-treated PBS in a conical flask and seal with Sealon film. On a heated stirrer (set to 6-7), inside the fume hood, mix until the milky solution turns colourless. Any cloudiness may be removed by adding a drop of 5M sodium hydroxide. Allow to cool before handling.

Safety

Paraformaldehyde is a rapid fixative and will cause harm if it comes into contact with the body.

WEAR GLOVES AND GOGGLES

PLEASE REFER TO THE APPROPRIATE SECTION IN THE CONTROL OF SUBSTANCES HAZARDOUS TO HEALTH (COSHH) REGULATIONS WHEN PREPARING/HANDLING THESE REAGENTS