DEHYDRATION Flashcards
Commonly Used Dehydrating Agents
A. Alcohol
B. Acetone
C. Dioxane
D. Cellosolve
E. Triethyl phosphate
F. Tetrahydrofuran
Removal of fixative and water from the tissue
Dehydration
Dehydrating time must be brief as much as possible and at a tissue-to-fixative ratio of____
1:10
CHARACTERISTICS OF IDEAL DEHYDRATING SOLUTION
• Rapid Action, with minimal tissue shrinkage and distortion
• Should not evaporate fast
• Able to dehydrate even fatty tissues
• Should not harden tissues excessively
• Should not remove stains
• Non-toxic, and not a fire hazard
Types of alcohol
Ethanol
Methanol
Butyl alcohol
• Best dehydrant under alcohol because it is fast-acting, mixes with water (it is miscible with water) and many organic solvents, and penetrates tissues easily
ETHANOL
Alcohol which is not poisonous
Not very expensive
Clear, colorless, flammable
Ethanol
Alcohol
Toxic
Ideal for blood smear preparation fixation
Methanol
Slow-acting alcohol
Made up of plant and animal microtechnique
Butyl alcohol
• Fastest dehydrant;
will only require______ to complete the dehydration process
ACETONE
30 minutes to 2 hour
Highly flammable, evaporates fast
Not recommended for routine dehydration purposes
Acetone
DIOXANE
• Also known as
Diethylene Dioxide
Has dual purpose
Dehydrating and clearing
Dioxane
tetrahydrofuran
Wrapping tissue in gauze and suspension to a bottle containing dioxane with anhydrous calcium oxide to quicklime
Weiseberger’s Method
DIOXANE
Example would be Glycol Monoethyl Ether
CELLOSOLVE
Rapid, prolonged storage does not cause distortion to tissues
• Toxic inhalation, skin irritant and combustible at 110-120F
• Alternative; propylene based glycol ethers
Cellosolve
• Soluble in alcohol, water, ether benzene, chloroform, acetone, and xylene
However, its disdavantage is it produces minimum shrinkage
Not commonly available in the market
TRIETHYL PHOSPHATE
Advantages:
• Staining procedures are improved
• Miscible in water and paraffin wax
Disadvantages:
• Dissolve fats
• Eye and skin irritant (conjunctival irritation)
Tetrahydrofuran
ADDITIVES TO DEHYDRATING AGENTS
• 4% Phenol
• Glycerol/alcohol mixture
ALCOHOL
● Done in ascending grades to avoid distortion of tissue:
70% ROH 90% ROH 100% ROH
(absolute alcohol)
For delicate tissues, start at
30%
will hasten dehydration rate (for urgent
exams)
37°C
To ensure complete dehydration:
○ Add at least ¼ deep layer of_______ at bottom of container, and cover with filter paper
○______ of________ indicates full saturation of dehydrating fluids with water. Thus alcohol must be changed with a fresh solution.
anhydrous Cu2SO4
Bluing
copper sulfate crystals
