What types of samples can be tested with combustion analysis?

Combustion analysis can be used on a wide range of solid, liquid, and gaseous sample types, including organic compounds, polymers, food matrices, soils, sediments, and pharmaceutical materials. The technique works by completely oxidizing a sample at high temperature, then measuring the resulting combustion gases to determine elemental composition, most commonly carbon, hydrogen, nitrogen, sulfur, and oxygen. The sections below explore which specific sample types are suitable and what factors influence reliable results.

Which materials are most commonly analyzed by combustion?

The most commonly analyzed materials in combustion analysis are organic and carbonaceous substances, including polymers, fuels, soils, food products, and pharmaceutical compounds. Any material that contains carbon, hydrogen, nitrogen, sulfur, or oxygen in measurable quantities is a suitable candidate for CHN analysis or CHNS/O elemental analysis by combustion.

Combustion analysis is widely adopted across industries precisely because it handles such a broad spectrum of materials. In practice, the technique is regularly applied to:

Organic chemicals and pure compounds for formula verification
Polymers, resins, and rubber materials for quality control
Fossil fuels, coal, coke, and biomass for energy content assessment
Soils, sediments, and geological materials for carbon and nitrogen profiling
Food and feed products for nutritional and quality analysis
Pharmaceutical active ingredients and excipients for purity testing

The common thread across all these materials is that they contain elements measurable by combustion. As long as a sample can be fully oxidized under controlled conditions, the method delivers accurate and reproducible elemental data.

Can combustion analysis be used on liquid and gas samples?

Yes, combustion analysis can be performed on liquid and gas samples, though the technique is most frequently associated with solid materials. Liquids such as oils, solvents, fuels, and aqueous solutions can be introduced into a combustion analyzer using sealed tin capsules or liquid sampling accessories designed to contain volatile matrices during ignition.

Gaseous samples present more specialized requirements. In most laboratory settings, gases are analyzed using dedicated gas-phase combustion or total organic carbon approaches rather than standard elemental combustion analyzers. However, for certain research and industrial applications, gaseous hydrocarbons can be introduced into combustion systems when the instrument is appropriately configured.

For liquid samples in routine quality control labs, the key practical consideration is accurate weighing and secure encapsulation to prevent evaporation before combustion begins. Volatile liquids in particular require careful handling to ensure the entire sample mass is accounted for in the elemental calculation.

What sample types are used in food and agriculture testing?

In food and agriculture testing, combustion analysis is commonly applied to grains, flours, animal feeds, meat products, dairy ingredients, oilseeds, and fertilizers. The primary application is nitrogen determination, which serves as the basis for calculating crude protein content using established conversion factors.

Protein determination by combustion has largely replaced older wet chemistry methods in modern food laboratories because it is faster, uses no hazardous reagents, and delivers highly reproducible results. Agricultural labs also use combustion to measure total carbon and nitrogen in soil samples, helping to assess soil organic matter content and nutrient cycling.

Beyond protein and nitrogen, sulfur determination in food matrices is relevant for certain quality and authenticity checks. Feed manufacturers routinely rely on combustion-based elemental analysis to verify nutritional specifications and meet regulatory labeling requirements. For Benelux food producers and agricultural testing facilities, combustion analysis is a central tool in both routine quality control and R&D workflows.

How are environmental and geological samples tested with combustion?

Environmental and geological samples tested with combustion analysis typically include soils, sediments, sludges, rocks, coal, and water treatment residues. The method is used to determine total organic carbon, total carbon, total nitrogen, and sulfur content, all critical parameters in environmental monitoring and geochemical profiling.

For environmental labs, total organic carbon in soil and sediment is an important indicator of contamination levels, organic matter decomposition, and ecosystem health. Combustion-based analysis provides a direct measurement of carbon fractions, often distinguishing between inorganic and organic carbon through temperature-controlled combustion sequences.

Geological applications extend to characterizing rock samples, coal seams, and mineral matrices. In water treatment facilities, combustion analysis of sludge and biosolids helps operators understand organic loading and support compliance reporting. Because environmental samples often contain complex, heterogeneous matrices, representative subsampling and thorough drying are essential steps before analysis begins.

What pharmaceutical and polymer samples work with combustion analysis?

Pharmaceutical samples suitable for combustion analysis include active pharmaceutical ingredients, excipients, drug intermediates, and formulated products. Polymer samples include synthetic resins, rubbers, coatings, adhesives, and fiber materials. Both categories are routinely tested to verify elemental composition, confirm molecular structure, and support quality control documentation.

In pharmaceutical development and quality control, combustion analysis supports identity confirmation of synthesized compounds and purity assessment of raw materials. The technique is particularly useful during early-stage synthesis, where confirming the carbon, hydrogen, and nitrogen ratios of a new molecule helps verify that the intended compound has been produced correctly. For exact compliance limits applicable to pharmaceutical materials, consult the relevant pharmacopeia or regulatory guidance.

For polymer and materials science applications, combustion analysis provides insight into formulation consistency. Manufacturers of technical polymers, specialty coatings, and composite materials use elemental data to monitor batch-to-batch reproducibility and detect contamination or raw material deviations. Sulfur content analysis is especially relevant for rubber compounding and fuel-related polymer applications.

How does sample preparation affect combustion analysis results?

Sample preparation has a direct impact on combustion analysis accuracy. Incomplete homogenization, residual moisture, incorrect sample mass, or inadequate encapsulation can all introduce errors into elemental results. Proper preparation ensures that the sample introduced to the analyzer is truly representative and fully combustible.

Several preparation factors deserve attention in any combustion analysis workflow:

Drying and moisture control: Many sample types absorb atmospheric moisture. Drying to a consistent moisture level before weighing prevents variability between measurements.
Grinding and homogenization: Heterogeneous materials such as soils, feeds, and polymers must be ground to a fine, uniform particle size to ensure the small analytical portion is representative of the bulk.
Accurate weighing: Combustion analyzers typically require sample masses in the milligram range. Precise weighing is critical, particularly for samples with low elemental concentrations.
Encapsulation: Solid and liquid samples are typically wrapped or sealed in tin or silver capsules. The capsule material must be appropriate for the sample type and the elements being measured.
Blank and standard verification: Running certified reference materials alongside samples confirms instrument performance and validates the calibration.

In practice, the quality of sample preparation often determines whether results are fit for purpose. Even the most precise combustion analyzer cannot compensate for a poorly prepared or unrepresentative sample.

How SciSPX supports combustion analysis in your laboratory

SciSPX supports laboratories across the Benelux with expert guidance on selecting, implementing, and maintaining combustion analysis instrumentation for elemental analysis applications. Whether you are working with food matrices, environmental samples, polymers, or pharmaceutical materials, the team brings both instrument knowledge and application-level expertise to help you get reliable results.

SciSPX’s support for combustion and elemental analysis includes:

Application consultation to match the right instrument configuration to your sample types
Installation, qualification (IQ/OQ), and validation services in line with GMP and GLP requirements
Training for lab technicians and QC staff on method development and sample preparation best practices
Ongoing service and preventive maintenance to keep instruments operating within specification

If you are evaluating combustion analysis solutions for your lab or need support with an existing setup, contact SciSPX to speak with a specialist.

Frequently Asked Questions

How do I know what sample mass to use for combustion analysis?

The optimal sample mass depends on the elemental concentration in your material and the detection range of your specific analyzer. As a general rule, samples with low carbon or nitrogen content require larger masses (often 100–500 mg), while high-carbon materials like polymers or pure organic compounds are typically analyzed at 1–5 mg to avoid detector saturation. Always consult your instrument’s method guidelines and run certified reference materials at your chosen mass to confirm the results fall within a validated calibration range.

What is the difference between CHN, CHNS, and CHNS/O analysis, and how do I choose the right one?

CHN analysis measures carbon, hydrogen, and nitrogen simultaneously, while CHNS adds sulfur determination, and CHNS/O additionally quantifies oxygen — either by direct measurement or by calculation as the difference from 100%. The right choice depends on your sample type and reporting requirements: food and agricultural labs typically need CHN or CHNS for protein and sulfur determinations, while pharmaceutical and polymer labs often require full CHNS/O to confirm molecular formulas. If you are unsure, selecting a CHNS/O-capable instrument gives you the most flexibility as your application needs evolve.

Can combustion analysis handle samples that contain halogens or heavy metals?

Samples containing halogens (fluorine, chlorine, bromine, iodine) or heavy metals can be analyzed by combustion, but they require special precautions to protect the instrument and ensure accurate results. Halogens can interfere with nitrogen and sulfur detection and may damage the combustion tube or detector system if not properly managed — silver wool or other trapping reagents are commonly used to capture halogenated gases before they reach sensitive components. Always notify your instrument supplier or application specialist when working with halogenated or metal-rich matrices, as reagent configurations and combustion conditions may need to be adjusted.

How often should combustion analyzers be calibrated, and what reference materials should I use?

Combustion analyzers should be calibrated at the start of each analytical run using certified reference materials (CRMs) with known elemental values traceable to recognized standards. Common calibration standards include acetanilide, sulfanilamide, and EDTA for CHN and CHNS applications, while soil and coal CRMs are preferred for environmental and geological workflows. Beyond daily calibration, a full multi-point calibration verification should be performed whenever consumables are replaced, after maintenance, or when a new sample type or matrix is introduced.

What are the most common reasons combustion analysis results are out of specification, and how can I troubleshoot them?

The most frequent causes of out-of-specification results include incomplete combustion due to insufficient oxygen flow or a degraded combustion tube, moisture in the sample or reagents introducing variability, inaccurate weighing at the milligram scale, and capsule contamination from handling. Start troubleshooting by running a fresh certified reference material — if the CRM result is also off, the issue is instrument-related (reagents, detector, or calibration); if only sample results are affected, focus on sample preparation and weighing technique. Keeping a logbook of CRM results over time is one of the most effective ways to catch instrument drift before it impacts real sample data.

Is combustion analysis suitable for trace-level elemental determination, or is it limited to bulk composition?

Combustion analysis is primarily a bulk elemental technique, best suited for determining major elemental fractions (typically from hundreds of ppm up to 100%) rather than ultra-trace concentrations at the ppb level. For very low sulfur or nitrogen concentrations — such as trace sulfur in high-purity fuels or nitrogen in ultra-clean polymers — specialized combustion-based analyzers with more sensitive detectors (such as chemiluminescence for nitrogen or UV fluorescence for sulfur) can extend detection limits significantly. If your application requires sub-ppm trace analysis, discuss your concentration range with your instrument specialist to confirm whether combustion analysis or an alternative technique such as ICP-MS is more appropriate.

How do I get started with combustion analysis if my laboratory is setting up the technique for the first time?

The best starting point is to clearly define your sample types, the elements you need to measure, your required throughput, and any regulatory or accreditation requirements (such as GMP, GLP, or ISO 17025) that will govern the method. From there, work with a knowledgeable supplier — like SciSPX for Benelux laboratories — to select an instrument configuration matched to your application, and plan for installation qualification (IQ/OQ), method validation, and staff training before moving to routine analysis. Investing time upfront in proper method development, reference material selection, and sample preparation protocols will pay dividends in data quality and long-term instrument reliability.

This content was generated with the help of AI and it may contain mistakes