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An elemental analyzer is a bench instrument that measures how much of certain elements a sample contains. In its most common form, a CHNS analyzer burns a small sample in oxygen and measures the carbon, hydrogen, nitrogen and sulfur that leave as gases. The same phrase is sometimes used more loosely for other elemental techniques; this page covers the combustion type and says where the others fit.
What an elemental analyzer is
Elemental analysis answers “which elements, and how much of each?” for a material. A combustion-based elemental analyzer does this for the light elements: carbon (C), hydrogen (H), nitrogen (N), sulfur (S) and, on some configurations, oxygen (O). Thermo Fisher describes its FlashSmart line as providing simultaneous analysis of CHNS by flash combustion and oxygen by pyrolysis.
Who uses it: Thermo Fisher lists soil, sediment, plants, fertilizers and sewage sludge; foods and feeds; lubricants, oils, biodiesel, polymers, plastics, carbon fibers, graphene and batteries; pharmaceutical products; and forensic samples as application areas for its organic elemental analyzers.
Techniques such as ICP-MS and ICP-OES are a different class: they measure trace metals and many other elements in solution. See the CASRAI guides on ICP-MS and the ICP-MS vs ICP-OES comparison.
How combustion analysis works
LECO describes the analysis chain for its 828 Series as follows, which is representative of the class:
- Combustion. The sample is combusted in pure oxygen so that it is completely oxidized and converted into measurable gases.
- Collection and mixing. The gases are collected in a ballast and mixed, and an aliquot is carried onward by a carrier gas, helium or argon.
- Detection. Carbon, hydrogen and sulfur are measured by non-dispersive infrared (NDIR) detection; nitrogen is measured by thermal conductivity (TC).
Thermo Fisher’s CHNS configurations use a thermal conductivity detector (TCD), with a flame photometric detector (FPD) offered for trace sulfur. Its application notes use helium or argon as carrier gas.
Which element needs which detector
| Element | Detection (LECO 828/928) | Detection (Thermo Fisher CHNS) |
|---|---|---|
| Carbon, hydrogen, sulfur | Non-dispersive infrared (NDIR) | Thermal conductivity detector (TCD); FPD for trace sulfur |
| Nitrogen | Thermal conductivity (TC) | Thermal conductivity detector (TCD) |
Nitrogen to protein (the Dumas method)
For protein work, the nitrogen released on combustion is converted through nitrogen oxides to N2 and measured, then a protein factor is applied to convert nitrogen to protein. LECO calls this the Dumas method. Thermo Fisher lists N/Protein as its own configuration.
Types and variants
| Type | Typical use | Key difference |
|---|---|---|
| CHN / CHNS (for example LECO CHN828, CNS928) | Carbon, hydrogen, nitrogen and, where fitted, sulfur in solids and liquids | LECO’s 828 measures N, C and H, with sulfur as an optional add-on; the 928 measures N, C and S |
| CN (for example LECO CN828, CN928) | Carbon and nitrogen only | Fewer elements measured than CHN or CHNS |
| CHNS/O (Thermo Fisher FlashSmart) | CHNS by flash combustion plus oxygen by pyrolysis | Adds oxygen determination to CHNS |
| N/Protein (Thermo Fisher) | Nitrogen with a protein conversion | Reports protein from nitrogen using a protein factor |
| Flash IRMS (Thermo Fisher) | Isotope-ratio measurements | Couples the combustion stage to an isotope-ratio mass spectrometer; see the CASRAI guide on isotope ratio mass spectrometry and delta notation |
Specifications that matter
Specifications differ by model even within one manufacturer’s range. The table compares two LECO models, as published by LECO, as an example of which numbers vary.
| Specification | LECO 828 Series | LECO 928 Series |
|---|---|---|
| Elements | N, C, H (S with optional add-on) | N, C, S |
| Maximum sample mass | Up to 1 g | Up to 3 g |
| Analysis time | As fast as 2.8 min | As fast as 5 min |
| Throughput | Up to 21 samples per hour | Up to 12 samples per hour |
| Autoloader | 30 positions standard, expandable to 120 | 100 positions |
| Furnace | Vertical, dual-stage | Horizontal, up to 1450 °C |
LECO also states a reduction tube life of over 4,000 samples.
How to choose
The differences below are the ones manufacturers document:
- Elements required. Configurations differ in which elements they report (CN, CHN, CNS, CHNS, CHNS/O, N/protein).
- Sample mass. LECO lists up to 1 g for the 828 and up to 3 g for the 928.
- Speed and sample count. Analysis time, hourly throughput and autoloader capacity differ between the two LECO models (see the table above).
- Isotopes. A flash combustion system can be configured for isotope-ratio work (Flash IRMS at Thermo Fisher).
Calibration is part of any quantitative method; see what is calibration for the general idea.
Safe use and handling basics
Combustion analyzers work with pure oxygen, high-temperature furnaces (LECO lists up to 1450 °C for the 928) and compressed carrier gases such as helium or argon. Follow the manufacturer’s operating manual and your site’s compressed-gas and hot-surface rules for installation, gas supply and maintenance.
Common mistakes
- Treating every elemental technique as one instrument class. Combustion CHNS analysis (light elements) and ICP-based techniques (metals and trace elements) answer different questions. The CASRAI analytical chemistry guide places both in context.
- Assuming a protein result is measured directly. The instrument measures nitrogen; protein is calculated by applying a protein factor.
- Comparing specifications across models without checking the basis. Mass, time and throughput figures belong to a specific model and configuration, as the 828 and 928 columns above show.
FAQ
What is elemental analysis?
Elemental analysis determines which elements a sample contains and how much of each. Combustion analysis measures carbon, hydrogen, nitrogen, sulfur and sometimes oxygen.
What does an elemental analyzer measure?
A combustion elemental analyzer reports the percentage of C, H, N and S (and O on CHNS/O configurations), depending on the model and configuration.
What is the Dumas method?
It is the combustion approach to nitrogen: nitrogen in the sample is converted to nitrogen gas and measured, and a protein factor converts it to protein where needed (LECO’s description).
Is an elemental analyzer the same as ICP-MS?
No. ICP-MS belongs to a different class of instruments; see the ICP-MS guide.
Sources
- Thermo Fisher Scientific, Organic Elemental Analysis (checked 2026-10-29).
- LECO Corporation, 828 Series (checked 2026-10-29).
Specifications are manufacturer-published figures for the named models and are not a ranking or recommendation of any product.
