Solvent · polar aprotic
Pyridine C5H5N
Rarely used as an HPLC mobile-phase component because of its strong UV absorbance (very high cutoff ~330 nm), toxicity and odor. Its main analytical roles: as a basic reaction/derivatization solvent and acid-scavenging base for GC derivatization (silylation, acetylation, trimethylsilylation reagents), as a solvent/base in Karl Fischer titration reagents (classical pyridine-based formulations), and as a general polar aprotic-basic GC solvent and complexing agent.
Compiled by Hemant RawatLast reviewed July 2026How we verify
Properties
- Formula
- C5H5N
- CAS number
- 110-86-1
- UV cutoff
- 330 nm
- Snyder polarity index (P′)
- 5.3
- Selectivity group
- III
- Eluotropic strength ε° (silica)
- —
- Boiling point
- 115.2 °C
- Viscosity (25 °C)
- 0.95 cP
- Refractive index (nD²⁰)
- 1.5093
- Density
- 0.982 g/mL
- Water miscibility
- miscible
- USP <467> class
- Class 2
Safety
- highly flammable (flash point ~20 C)
- acutely toxic / harmful by inhalation, ingestion and skin contact
- hepatotoxic (liver) and CNS toxicity
- suspected reproductive toxicity
- IARC Group 3 (not classifiable as to carcinogenicity)
- strong penetrating odor / lachrymator
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 Pyridine mixes with
Miscible with: 1-Propanol, 1,2-Dichloroethane, 1,4-Dioxane, 2-Propanol, Acetic acid, Acetone, Acetonitrile, Benzene, Carbon tetrachloride, Chloroform, Cyclohexane, Dichloromethane, Diethyl ether, Dimethyl sulfoxide, Ethanol, Ethyl acetate, Iso-octane, Methanol, Methyl ethyl ketone, Methyl isobutyl ketone, MTBE, n-Butanol, n-Butyl acetate, n-Heptane, n-Hexane, N-Methylpyrrolidone, n-Pentane, N,N-Dimethylacetamide, N,N-Dimethylformamide, tert-Butanol, Tetrahydrofuran, Toluene, Triethylamine, Water.
Check any specific pair on the interactive miscibility chart.
Using Pyridine in HPLC/GC
Rarely used as an HPLC mobile-phase component because of its strong UV absorbance (very high cutoff ~330 nm), toxicity and odor. Its main analytical roles: as a basic reaction/derivatization solvent and acid-scavenging base for GC derivatization (silylation, acetylation, trimethylsilylation reagents), as a solvent/base in Karl Fischer titration reagents (classical pyridine-based formulations), and as a general polar aprotic-basic GC solvent and complexing agent.
Its Snyder polarity index is 5.3 (selectivity group III), and its UV cutoff of 330 nm limits low-wavelength 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.
Related solvents
Other selectivity group III to compare with Pyridine.