DEHYDRATION

Dehydration

Removal of all water from tissues after fixation to prepare for embedding in paraffin wax

Prevents water interference in clearing and infiltration steps.

Purpose of Dehydration

At least 10x the volume of the Tx

Volume of Dehydrating Agent

Ethanol

Most commonly used; fast-acting, non-toxic, and suitable for fatty tissues

Methanol

Toxic

used for blood and Tx smear preparation

Butanol

Used in plant and animal microtechniques.

Isopropanol

Can be an ethanol substitute and used in microwave techniques.

During clearing, can be used as substitute for Xylene.

Acetone

Both fixative and dehydrating agent.

Rapid but evaporates easily; used for urgent biopsies.

Diethylene Dioxide (Dioxane)

Can act both as dehydrating and clearing agent.

Tissues tend to ribbon poorly.

Extremely dangerous / toxic to man.

Ethylene Glycol Monoethyl Ether (Cellosolve)

Toxic by ingestion, inhalation and skin contact

Toxic to reproductive fetal, urinary and blood systems

Ethylene Glycol Monoethyl Ether (Cellosolve)

Combustible at 110-120 degF or 43-48 degC

Decomposes upon exposure to sunlight and removes aniline dyes

Triethylphosphate

Causes only minimum shrinkage.

Dehydrate sections and smears following certain stains.

Tetrahydrofuran (THF)

Can dehydrate and clear tissues

Vapors cause nausea, dizziness, and headache.

Tetrahydrofuran (THF)

Dehydrating agent that is both a skin & eye irritant.

With offensive odor and may cause conjunctival irritation.

Ethanol, Propylene oxide, Acetonitrile

EM Dehydratin Agents

Molliflex, 4% Phenol, Glycerol Alcohol Mixture

Dehydrating Agent Additives for Duly Hard Tx

Tx maceration

Too low concentration (40%)

Hardens outer Tx, preventing deeper penetration

Too High concentration (95%)

Start with 30% alcohol

For delicate Tx

Color if there is still H2O

Blue