Cacodylate

An organoarsenic compound used in biochemistry and medicine

Cacodylate refers to the anion derived from cacodylic acid, an organoarsenic compound with the formula (CH₃)₂AsO₂⁻. It is commonly encountered as sodium cacodylate, a salt that is used in various biochemical applications.

Structure and Properties

Cacodylate is an organoarsenic compound characterized by the presence of arsenic bonded to two methyl groups and an oxygen atom. The structure of the cacodylate ion is planar, with the arsenic atom at the center. The chemical formula for the cacodylate ion is C₂H₆AsO₂⁻, and it has a molar mass of 137.99 g/mol.

Cacodylate is known for its stability in aqueous solutions, which makes it useful as a buffering agent in biological and biochemical research. The pKa of cacodylic acid is approximately 6.2, allowing it to act as an effective buffer in the pH range of 5.5 to 7.5.

Applications

Cacodylate is primarily used as a buffering agent in biochemistry and molecular biology. It is particularly useful in the preparation of biological samples for electron microscopy, where it helps to maintain the pH and osmolarity of the sample environment.

In electron microscopy, sodium cacodylate buffer is often used during the fixation process to preserve the ultrastructure of cells and tissues. The buffer helps to stabilize the pH during the fixation with glutaraldehyde or osmium tetroxide, which are commonly used fixatives.

Safety and Toxicity

Cacodylate compounds, like other organoarsenic compounds, are toxic and should be handled with care. Exposure to cacodylate can lead to arsenic poisoning, which can cause a range of health effects including skin lesions, cardiovascular disease, and cancer.

Proper safety precautions should be taken when handling cacodylate, including the use of personal protective equipment such as gloves and goggles, and working in a well-ventilated area or fume hood.

History

The term "cacodylate" is derived from the Greek word "kakodes," meaning "foul-smelling," due to the compound's characteristic garlic-like odor. Cacodylic acid and its derivatives were first synthesized in the 18th century and have been studied for their chemical properties and potential applications in medicine and agriculture.

Also see

• Cacodylic acid
• Arsenic
• Buffer solution
• Electron microscopy

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