Isopropanol (IPA) — Frequently Asked Questions

Water is needed to denature the proteins in microorganisms, and it slows evaporation, so the solution stays in contact with the surface long enough to act. Around 70% alcohol in water is therefore more effective than the pure solvent. Sanitiser makers buy 99.9% IPA and dilute it, because that gives full control over concentration and avoids paying to transport water.

High-purity IPA dissolves flux residues, oils and fingerprints and evaporates completely, leaving no water or residue to cause marks or corrosion. Water content and non-volatile residue are the key limits. For sensitive assemblies, specify those limits and check them on the certificate of analysis; some semiconductor processes use a separate electronic grade with metal-ion limits.

Isopropanol has a flash point of about 12 °C, so its vapour can ignite at normal room temperature. Store it in closed, earthed containers in a cool, well-ventilated flammable-liquids store, away from ignition sources and oxidisers. Bond and earth equipment during transfer and use explosion-protected electrical equipment where vapour can build up.

Both are short-chain alcohols that mix with water, but isopropanol dissolves oils and some resins better, evaporates slightly more slowly and is not generally subject to alcohol excise controls in the way ethanol is. Ethanol is preferred where it must be consumed or where regulations favour it. For cleaning and many industrial uses, IPA is often the simpler choice.

Isopropanol is transported as UN1219, ISOPROPANOL, Class 3 flammable liquid, packing group II, under ADR, the IMDG Code and IATA rules. It needs UN-approved packaging, Class 3 labels and a dangerous goods declaration for sea freight. Keep the same description on the invoice, packing list and bill of lading, and confirm the details against section 14 of the safety data sheet.