compound fixatives

Question 1

B5( 3)

Answer 1

no longer used due to toxicity

mercuric chloride
sodium acetate
formaldehyde

after fixation any remaining tissue would have tp be transferred to NBF or 70% alcohol

may form formalin pigment

Question 2

bouins

Answer 2

*picric acid
formaldehyde
acetic acid

lyses RBCs- false neg

iron and calcium are dissolved - false neg but useful for slight decalcification

great for trichrome stain or soft delicate structure preservation

yellow color must be washed out ( picric acid )
- use 50-70% alcohol or 70% alcohol with lithium carbonate

causes deterioration over time - store in 70-80% alcohol after 24 hrs

cannot be used for EM

may form formalin pigment

acetic acide swells, picric acid shrinks
formaldehyde hardens while picric acid softens

Question 3

gendre solution

Answer 3

95% alcohol
picric acid
glacial acid *

basically alcoholic bouins

preserves carbohydrates, especially glycogen - avoid glycogen streaming with alcohol *

remove yellow pigment with 80% alcohol

Question 4

hollande solution

Answer 4

copper acetate
picric acid
formaldehyde
acetic acid

decalcifies small bone specimens ***

wash before tissue processing

good for special stains

Question 5

Zenker and Helly

Answer 5

stock solution contains 
mercuric chloride 
potassium dichromate 
sodium sulfate 
water ( optional ) 

both produce mercury pigment **

wash on water to prevent chromate pigment

store wet tissue in 70-80% alcohol

silver staining is unsatisfactory **

Question 6

Zenker

Answer 6

add acetic acid ( A to Z)

stable

will lyse RBCs giving false neg

recommended for phosphotungstic acid staining

Question 7

Helly

Answer 7

add formaldehyde

not stable - formaldehyde is a reducer, potassium dichromate is an oxidizer

can produce formalin pigment

will not lyse RBCs

Question 8

Orth Solution

Answer 8

SPF

potassium dichromate
sodium sulfate
water
formaldehyde ( added just before use )

demonstrate chrimaffin granules - pheochromocytoma diagnosis

increased eosin staining

Question 9

Zamboni Solution ( buffered picric acid - formaldehyde) PAF

Answer 9

paraformaldehyde
aqueous picric acid
phosphate buffer

may be used for EM ( same as gluteraldehyde )

Question 10

alcoholic Zinc Formalin

Answer 10

zinc chloride
water
isopropanol alcohol
formaldehyde

fixes faster than aqueous zinc solution ( 1.5x)

good for post fixation -enhances nuclear detail vs NBF

rush specimen

Question 11

unbuffered aqueous zinc formalin

Answer 11

zinc sulfate
water
formaldehyde

wash before NBF to prevent precipitate

Question 12

non - additive fixatives

Answer 12

acetone and alcohol

very flammable

drastic hardening

Question 13

acetone

Answer 13

fix frozen section sfor immunochmestry *

fix brain for rabies stain *

hardening

Question 14

Alcohol

Answer 14

methyl used for fixing smears and touch prep

ethyl used fir preservation of water soluble tissue elements

• glycogen ( prevents glycogen streaming)
• urate crystals ( preserve urate crystals )

ethyl preserves most pigments and dissolves fat

Question 15

Carnoy solution

Answer 15

absolute ethyl alcohol
chloroform
acetic acid

preserves glycogen anf nucleius

false neg acid -fast bacilli ***such as TB

Question 16

3 types of pigment

Answer 16

formalin- keep pH above 6
mercury
chrome

Question 17

how to remove the 3 types of pigment

Answer 17

formalin( acid hematin)

• alcoholic picric acid
• alcoholic ammonium
• alcoholic potassium hydroxide

mercury
- iodine followed by sodium thiosulfate

chrome pigment
- 1% HCL in 70% alcohol however may decrease rather than remove pigment