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.