“Hexane” on a purchase request can mean several different things. It may be a mixture of six-carbon isomers or nearly pure n-hexane. The label can say technical, extraction, GC, HPLC or ACS reagent. Each grade is defined by different tests, so picking by purity percentage alone often leads to paying for specifications you do not need, or missing the one that matters.
This article explains what the common grades mean, how to read a certificate of analysis (COA), and how to match a grade to a job.
What “hexane” actually means
Commercial hexane is usually a blend of C6 isomers, not a single compound. A typical blend contains roughly half n-hexane, with 3-methylpentane, 2-methylpentane and methylcyclopentane making up much of the rest. n-Hexane is the straight-chain molecule, with a boiling point of about 69 °C. The practical differences between the two are covered in our hexane vs n-hexane FAQ.
The key point is that “99%” can describe two very different things. It may be the n-hexane content alone, or the sum of all hexane isomers. Always check which one the COA reports.
Hexane grades explained at a glance
Grade names are not fully standardised across suppliers, so treat the table as a guide and always read the actual specification sheet.
| Grade | Typical use | What it is usually defined by |
|---|
| Technical / industrial | Cleaning, degreasing, adhesives, general solvent use | Boiling range, n-hexane or total hexane content, basic impurity limits |
| Extraction grade | Solvent extraction, such as edible oil processing | Narrow boiling range, low residue, limits on impurities that affect the final product |
| GC grade | Gas chromatography sample preparation and dilution | Low impurity peaks in the chromatogram |
| HPLC grade | Liquid chromatography mobile phase | UV transmittance, low UV cutoff, low residue |
| ACS reagent | General laboratory work to a published reagent specification | Assay, residue after evaporation, water, acidity and other limits |
Published laboratory specifications show how much the numbers vary:
- Some ACS reagent n-hexane products are specified at 95% or more n-hexane, and 98.5% or more for hexane isomers plus methylcyclopentane.
- Other ACS reagent hexane products are specified at only 60% or more n-hexane, with a very high figure for total hexanes by GC.
- Some n-hexane products for UV and HPLC use list a minimum GC assay of 99.0% and a minimum UV transmittance at 195 nm.
- Some HPLC-grade n-hexane products list a UV cutoff at or below 195 nm.
So “ACS reagent” does not guarantee a high n-hexane content. “HPLC” is defined mainly by optical properties, not just purity.
How to read a hexane COA
A COA lists measured results against specification limits. These are the lines that usually matter.
- Assay (GC): The percentage found by gas chromatography. Check whether it is n-hexane alone or total hexane isomers.
- Distillation range: A narrow range suggests a more uniform composition. A wider range is normal for isomer blends.
- Water: Matters for moisture-sensitive work.
- Residue after evaporation: Shows how much non-volatile material stays behind. Reagent-grade specifications often set very low limits here.
- Acidity and colour: Basic purity checks used in reagent specifications.
- UV absorbance and cutoff: Critical for HPLC. A lower cutoff lets the detector work at shorter wavelengths.
- Benzene and other aromatics: Relevant for extraction and food-related uses. Ask for the limit and the test method, and do not assume it is covered.
The test method matters as much as the number. A result from gas chromatography and a result from a different method are not directly comparable.
Common mistakes when choosing a grade
- Assuming higher purity is always better. For degreasing or bulk extraction, an HPLC-grade solvent adds cost without benefit.
- Reading one number. An assay says little about residue, water or UV behaviour, which decide whether the solvent works in your process.
- Confusing n-hexane content with total hexanes. The same percentage can describe different compositions.
- Treating grade names as universal. “Extraction grade” and “technical grade” have no single global definition, so compare specifications, not names.
- Ignoring batch consistency. For analytical work, ask for a COA for the specific lot you receive.
Health and safety basics
n-Hexane is highly flammable. Its flash point is well below room temperature, at about -23 °C, and its vapours are heavier than air, so they can collect at low points and travel to ignition sources.
It is also a known neurotoxin. Repeated exposure can damage the peripheral nerves, and the effect is linked to a metabolite called 2,5-hexanedione. Symptoms include numbness and tingling in the hands and feet and, in more severe cases, muscle weakness.
Published exposure limits differ by organisation. NIOSH recommends 50 ppm as a time-weighted average, and ACGIH uses the same 50 ppm figure. The current enforceable OSHA permissible limit is still 500 ppm, because a stricter 1989 limit was vacated by a court in 1992. Many safety professionals therefore work to the lower 50 ppm figure. Always follow the safety data sheet (SDS) and local regulations for ventilation, grounding, storage and protective equipment.
A simple selection checklist
- Define the job. Cleaning, extraction, or analytical work?
- Decide what must be controlled. Boiling range, residue, water, UV absorbance, or specific impurities?
- Check the basis of the assay. n-Hexane alone, or total hexane isomers?
- Ask for the COA and the SDS for the exact grade and lot.
- Match, don’t maximise. Choose the lowest grade whose specification covers your critical parameters.
- Confirm packaging and handling against the SDS and local rules before ordering.
For product details, see our n-hexane products and hexanes range. For background on how HPLC measurements work, see what HPLC measures.
FAQ
Is there a difference between hexane and n-hexane?
Yes. “Hexane” often means a mixture of C6 isomers, while n-hexane is the single straight-chain compound. Some commercial hexane contains only about half n-hexane.
What is GC grade hexane?
A grade with very low impurity peaks when run on a gas chromatograph, so it does not interfere with the analysis. Check the supplier’s specification for the exact limits.
What is HPLC grade hexane?
A grade defined mainly by UV transmittance and a low UV cutoff, so it does not mask the detector signal. Published examples show cutoffs at or below 195 nm.
What is ACS reagent grade hexane?
Hexane meeting a published reagent specification. The n-hexane content varies by product, from at least 60% to at least 95%, so read the assay basis.