GPHT LAB - Fixation Handouts Flashcards
grp of fixatives satisfactory for routine paraffin sections, frozen sections, and for EM
aldehyde fixatives
gas produced by oxidation of MetOH
formaldehyde
HCHO soluble in water to the extent of ___ by weight
40%
powerful RA, used in the make up of Helly’s fluid
formaldehyde
purest solution (how many percent) of formaldehyde
40%
routine formalin sol’n how many percent
10%
how to prep routine formalin sol’n
10 ml strong HCHO
90 ml H20 or saline
dilution of routine formalin sol’n
1:10
usual fixation time of HCHO
12-24 hrs
often becomes turbid
commercial HCHO
why does commercial HCHO become turbid after prolonged storage
due to formation of paraformaldehyde which is caused by HCHO polarization
presence does not impair fixing qualities of HCHO
paraformaldehyde
removal of formalin pigments methods (3)
Kardasewitsch’s
Lillie’s
Picric Acid Method
what method of removal of formalin pigments
section placed for 5 min - 2 hrs in 70% EtOH, 28% NH3 water
Kardasewitsch’s
what method of removal of formalin pigments
section placed for 1-5 min in acetone, 3 vol H2O2, 28% NH3 H20, rinsed in 70% EtOH
Lillie’s
section placed for 5 min - 2 hrs in std solution of picric acid
washed in running water for 11-15 min
picric acid method
aldehyde MW 100 or 2 formaldehyde residues linked by a striaght 3C chains
glutaraldehyde
best used for small fragments and small needle biopsies
2.5% glutaraldehyde
for larger tissue not exceeding 4mm in thickness, for 12-24 hrs at RT
4% solution of glutaraldehyde
polymer of formaldehyde, white powder
paraformaldehyde
used in a 4% strength at 4c
paraformaldehyde
frequently used in saturated soln
mercuric chloride
solubility of HgCl2 in water at RT
7%
in removing mercuric chloride granules, sections are placed in alcoholic iodine for 1-2 min. give exact composition of alcoholic iodine
0.5 ml iodine in 100 ml 70% EtOH
