Elemental & Composition

CHNS-O

Carbon, hydrogen, nitrogen, sulfur and oxygen by combustion

CHNS-O analysis burns a small weighed sample and measures the gases released to give its carbon, hydrogen, nitrogen, sulfur and oxygen content in weight %. It is the standard check of composition and purity for new compounds.

1 test optionC, H, N, S and O in weight %Typically 1–3 mg per runTypical turnaround 4–6 working days
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CHNS-O measurement principleIllustrative
Tin capsuleHe + O₂CombustionReductionGC columnTCDN₂CO₂H₂OSO₂
A sample burned, its gases countedIllustrative
01 / Overview

What is CHNS-O?

A few milligrams of sample, sealed in a tin capsule, drop into a furnace at around 1000 °C with a pulse of oxygen. It burns completely to CO₂, H₂O, nitrogen oxides and SO₂; hot copper reduces the nitrogen oxides to N₂, and the gases are separated and measured by a thermal conductivity detector.

Oxygen is measured in a separate run by pyrolysis, where it is converted to CO. The method gives bulk composition, typically within ±0.3% absolute for pure compounds, which makes it the usual way to confirm the empirical formula and purity of synthesised materials.

02 / How it works

How it works

  1. 01

    Sample is weighed

    A few milligrams are weighed into a small tin capsule on a microbalance.

  2. 02

    Flash combustion

    The capsule drops into a furnace at around 1000 °C with oxygen and burns completely.

  3. 03

    Gases are separated

    Copper reduces nitrogen oxides to N₂, then a column separates N₂, CO₂, H₂O and SO₂.

  4. 04

    Detector records peaks

    A thermal conductivity detector gives a peak for each gas, calibrated against standards.

03 / What it measures

What it measures

Carbon & hydrogen content

Weight % of C and H, measured as CO₂ and H₂O.

Useful forOrganic compounds, polymers, fuels

Nitrogen content

Weight % of N, for example in amines or nitrogen-doped materials.

Useful forN-doped carbons, biomass, fertilisers

Sulfur content

Weight % of S, measured as SO₂.

Useful forFuels, rubbers, sulfonated polymers

Oxygen content

Weight % of O by pyrolysis, measured as CO.

Useful forBiomass, oxidised carbons, organics

Purity & empirical formula

Compare found and calculated values for a newly made compound.

Useful forSynthesised molecules, publication data
04 / Test options

Choose the CHNS-O options you need

1 option · none added yet

CHNS-O test options
05 / Sample requirements

Sample requirements

Accepted forms
Dry, homogeneous solids and powders; non-volatile liquids
Quantity
At least 10 mg, to allow duplicate runs
Elements
State which of C, H, N, S and O you need
Expected values
Share the formula or expected composition if known
  • Dry the sample; residual solvent or water skews C and H
  • Grind to a fine, homogeneous powder
  • Sealed, labelled vial with the expected formula
  • No volatile or air-sensitive samples without discussing first
  • No fluorine-rich samples without telling the lab first

Hazardous or air-sensitive samples: mention it in your request, and attach the MSDS if you have one.

06 / Results & turnaround

Results & turnaround

What you receive

  • Weight % of C, H, N, S and/or O
  • Replicate values with mean
  • Comparison with calculated values, if a formula is given
  • Calibration standard details
  • Report PDF

Turnaround & pricing

Typically 4–6 working days after samples reach the lab.

Price confirmed in your quotation, depending on user type, options and number of samples.

Sample report · IllustrativeExample carbon content62.4 wt%Illustrative — not measured sample data
07 / Limitations

When CHNS-O isn't the right fit

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