Solvent · polar aprotic
Acetonitrile C2H3N
Also: ACN, MeCN
Primary organic modifier in reversed-phase HPLC/UHPLC mobile phases (offers different, often better selectivity vs methanol; low viscosity gives lower backpressure; very low UV cutoff ~190 nm enables low-wavelength UV detection). Standard strong solvent in gradient RP-LC and LC-MS (volatile, MS-compatible). Widely used for sample dilution/reconstitution, protein precipitation in bioanalysis, and as a diluent; also a GC solvent and extraction solvent (immiscible with alkanes allows ACN/hexane defatting partitions).
Compiled by Hemant RawatLast reviewed July 2026How we verify
Properties
- Formula
- C2H3N
- CAS number
- 75-05-8
- UV cutoff
- 190 nm
- Snyder polarity index (P′)
- 5.8
- Selectivity group
- VIb
- Eluotropic strength ε° (silica)
- 0.52
- Boiling point
- 81.6 °C
- Viscosity (25 °C)
- 0.37 cP
- Refractive index (nD²⁰)
- 1.3441
- Density
- 0.782 g/mL
- Water miscibility
- miscible
- USP <467> class
- Class 2
Safety
- highly flammable (flash point ~2-6 C, closed cup)
- acutely toxic - metabolized to cyanide (hydrogen cyanide) in vivo
- harmful if swallowed, inhaled, or absorbed through skin
- serious eye irritant
- vapor forms explosive mixtures with air
Reference only. Solvents can be flammable, toxic, or peroxide-forming. Always consult the Safety Data Sheet (SDS) and your lab's protocols before handling.
What Acetonitrile mixes with
Miscible with: 1-Propanol, 1,2-Dichloroethane, 1,4-Dioxane, 2-Propanol, Acetic acid, Acetone, Benzene, Chloroform, Dichloromethane, Diethyl ether, Dimethyl sulfoxide, Ethanol, Ethyl acetate, Methanol, Methyl ethyl ketone, Methyl isobutyl ketone, MTBE, n-Butanol, n-Butyl acetate, N-Methylpyrrolidone, N,N-Dimethylacetamide, N,N-Dimethylformamide, Pyridine, tert-Butanol, Tetrahydrofuran, Toluene, Triethylamine, Water.
Partially miscible with: Carbon tetrachloride, Cyclohexane — mix only over a limited range.
Immiscible with: Iso-octane, n-Heptane, n-Hexane, n-Pentane — these form two layers.
Check any specific pair on the interactive miscibility chart.
Using Acetonitrile in HPLC/GC
Primary organic modifier in reversed-phase HPLC/UHPLC mobile phases (offers different, often better selectivity vs methanol; low viscosity gives lower backpressure; very low UV cutoff ~190 nm enables low-wavelength UV detection). Standard strong solvent in gradient RP-LC and LC-MS (volatile, MS-compatible). Widely used for sample dilution/reconstitution, protein precipitation in bioanalysis, and as a diluent; also a GC solvent and extraction solvent (immiscible with alkanes allows ACN/hexane defatting partitions).
Its Snyder polarity index is 5.8 (selectivity group VIb), and its UV cutoff of 190 nm is low enough for most UV detection.See what the polarity index means and the full UV cutoff table.
Sources
- University of Toronto (TRACES) — Burdick & Jackson — Solvent UV cutoff table (absorbance = 1 AU, 1 cm cell)
- Stenutz / L. R. Snyder — Solvent polarity index (P′) and selectivity groups
- NIST — Chemistry WebBook — thermophysical properties (BP, density, refractive index)
- PubChem (NIH/NLM) — Compound property records (physical constants, CAS, formula)
- USP <467> / ICH Q3C — Residual Solvents — solvent classification (Class 1/2/3)
Values are compiled from public references and were last verified July 2026. See ourmethodologyfor how we source and verify. Always confirm critical values against primary references and the SDS.