Combustion Analysis Versus Spectrometric Methods

Elemental analyzers are also frequently called combustion analyzers because the combustion of the sample is an essential step of the analysis process. ELTRA analyzers utilize various types of furnaces with different temperatures for combustion. The maximum temperatures range from 1,000 °C in a resistance-heated quartz tube furnace up to more than 3,000 °C in an impulse furnace for the analysis of the elements O, N, H in metals. The choice of the best suited analyzer depends on the sample to be analyzed and its matrix. There are organic sample matrices with a high carbon content, such as coal, oil, food, and inorganic sample matrices, such as metals, ceramics or carbides. For sample materials such as cement or soil various analyzers are suitable for measuring the element concentrations.

For more than 30 years ELTRA has been among the leading manufacturers of elemental analyzers. The line of instruments covers a measuring range from a few ppm to 100 % and reliably and accurately analyzes organic as well as inorganic materials.

Spectrometric Methods

For the determination of C, H, N, S, O concentrations in solids, different methods are applied in laboratories and production. Wet chemical methods such as AAS or ICP OES are not only time-consuming and cost-intensive, they are also not suitable for analyzing gaseous sample components (N, O, H). For direct analysis of solid materials methods such as x-ray fluorescence, spark spectrometry or glow discharge are well established. However, these spectrometric procedures have some disadvantages. Whereas elemental analyzers are suitable for metallic and non-metallic materials, regardless of the sample geometry (e. g. wires, powders, liquids), spectrometric methods require a plane, defined surface and are often limited to the analyses of metallic materials. Other limiting factors of spectrometric methods are inhomogeneous samples, changing sample matrices and the excitation and detection of light elements.

Advantages of Combustion Analysis

Elemental analyzers offer the benefit of simple and fast analysis with high sample weights up to several grams. The required sample preparation is rudimentary and only involves size reduction. ELTRA elemental analyzers reliably measure concentrations from a few ppm up to 100%. The measurement results are usually available within minutes, depending on the method used, allowing for a high sample throughput. ELTRA analyzers also offer the possibility of carrying out fractional analysis which not only provides the total element content but also the chemical origin. For example, the carbon content of a soil sample consists of total organic carbon (TOC) and total inorganic carbon (TIC). Both parameters can be determined with ELTRA analyzers.

Variety of Applications

ELTRA analyzers are used in production, quality control, and research and development. There is a very wide array of sample matrices that can be analyzed for their C, H, N, S, O concentrations and thermogravimetric parameters with ELTRA analyzers.

Fuels

To control the heating value in fuels such as coal, coke, waste, wood, or oil, analysis of the carbon content is necessary. In addition, efficient management of the desulfurization plant requires the control of the sulfur content. Both parameters (and optionally the hydrogen content) can be determined reliably with ELTRA’s CHS-580 series.

Building Materials

Cement plants face the challenge to examine the carbon and sulfur content of both the fuels used as well as of the cement. The sulfur content significantly influences the “aging” of the cement due to acidification. In order to analyze both matrices reliably, the CS-2000 is the ideal instrument with its unique combination of resistance and induction furnace (ELTRA Dual Furnace Technology).

Ceramic Materials

As a result of its thermal characteristics, silicon carbide forms the basis of many mixtures in refractory linings in industrial furnaces. The proportion of SiC can be reliably and accurately determined in the ELEMENTRAC CS-i indirectly via the carbon content.

Metals

The content of C, H, N, S and O influences properties such as ductility, corrosion tendency, or brittleness of almost any metal (e.g. steel, iron, copper, titanium, nickel). An effective ONH analysis is possible by means of an electrode furnace (ELEMENTRAC ONH-p series); for CS analysis with an induction furnace, the ELTRA ELEMENTRAC CS-i is used.

Plastics

By means of thermogravimetric analysis, moisture or filler contents of plastics can be determined in one analysis run. In the context of quality control, the thermal decomposition behavior provides valuable information about errors in the mixing ratio and in processing. The TGA Thermostep is ideally suited for this application.

Soils

In this matrix, carbon is present in different bonding forms. Total organic carbon (TOC) and total inorganic carbon (TIC) are suitable standard parameters for the characterization of soils. ELTRA offers different analyzers for this application: The CW-800 series can apply different temperatures and carrier gases for the determination of TOC and TIC (temperature method). Alternatively, acid-treated samples can be analyzed with the ELEMENTRAC CS-i or CS-580.

Glass

The amount of SO₃ in the glass melt influences the extent of bubble formation in the glass production. In order to control this glass fining process, the ELEMENTRAC CS-i is the ideal analyzer for the determination of the sulfur content.

Food

The quality of some foods, such as flour, is among other factors influenced by the ash content. 100 g flour of type 550 contains 550 mg of ash which indicates the mineral content in the flour. These values can be conveniently determined with the ELTRA TGA Thermostep.

Product Overview ELTRA Analyzers

This information has been sourced, reviewed and adapted from materials provided by ELTRA GmbH.

For more information on this source, please visit ELTRA GmbH.