Acetonitrile: Properties and Applications

What is acetonitrile and why is it used in laboratories?

Acetonitrile (CH₃CN), also known as ethanenitrile, is a colourless, volatile liquid with a low boiling point (81.6 °C). It is a polar aprotic solvent, meaning it dissolves a wide range of organic and inorganic compounds without donating protons. Its high dielectric constant and low viscosity make it ideal for HPLC, where it enhances separation efficiency and reduces backpressure. It is also used in protein precipitation, nucleic acid extraction, and as a reaction medium in organic synthesis. Due to its compatibility with UV detection, it is frequently used in analytical workflows requiring low UV absorbance.

How should acetonitrile be handled and stored?

Acetonitrile is flammable and poses health hazards, including respiratory irritation and potential neurotoxicity. It must be stored in tightly sealed, amber-coloured containers away from heat and ignition sources. In laboratory settings, it should be handled in well-ventilated areas or fume hoods. Regulatory compliance with GHS, REACH, and TSCA is essential. High-purity grades (e.g., HPLC grade, ACS reagent grade) are required for sensitive applications. Always consult the Safety Data Sheet (SDS) and Certificate of Analysis (CoA) before use.

Related concepts

Acetonitrile is often compared with methanol and tetrahydrofuran (THF) in chromatographic applications. Its low UV cutoff makes it superior for UV-Vis detection. It is also used in the synthesis of pharmaceuticals, agrochemicals, and as a solvent in polymer processing.