Carbon Analysis – How the Carbon Content of a Sample is Determined by LSM Analytical Services

Background

LSM Analytical Services offer a large and diverse range of modern analytical testing facilities that cater for a vast range of industry sectors. LSM’s success has been achieved by building on a strong reputation for low cost, fast accurate turnaround. The laboratory activities are backed up by accreditation to the ISO 17025 (UKAS) and 9001:2000 laboratory and quality management standards. LSM is able to offer complete analytical solutions from its internationally recognised team of technical experts, with in depth knowledge, allowing its customers to benefit from impartial guidance.

LSM’s range of analytical services includes:

•        X-Ray Fluorescence Spectrometry (XRF)

•        X-Ray Diffraction (XRD)

•        ICP Optical Emission Spectrometry (ICP-OES)

•        Atomic Absorption Spectrometry (AAS)

•        Carbon, Sulphur, Nitrogen, Oxygen Analysers

•        Boron analysis by the Neutron Transmission method

•        Colorimetric and Volumetric Analysis

•        Particle Size Analysis

Carbon Analysis

LSM Analytical Services large range of analytical techniques includes instrumentation for Carbon analysis.

The Principle of Carbon Analysis

The principle of Carbon analysis is to oxidise the sample by heating in an Oxygen atmosphere to form CO₂, which is then measured by infrared detector.

Heating Samples for Carbon Analysis

The heating is generally done in a high frequency induction furnace as this provides both speed and accuracy. The sample is placed in a ceramic crucible and an accelerator is often added to ignite the sample and can also act as a flux to dissolve any oxide skins to improve melt fluidity, which allows the carbon in the sample to be oxidised in a short time. It is imperative that complete combustion is achieved in order to gain accurate results.

Accelerators

There are a large range of accelerators used and the choice depends on the base material being analysed. One feature of any accelerator is a low carbon (and Sulphur as this is often analysed for in a similar way) content.

Ensuring Accuracy During Carbon Content Determination

A key issue in carbon determination by this method is the purity of the Oxygen gas used. Typical impurities include CO₂ and CH₄. CH₄ can be oxidised at the temperatures involved in the test to CO₂ + H₂O, so for accurate results the effects of these impurities have to be resolved in the test method. This can be done in a number of ways, for example by using high purity Oxygen or by employing an in line gas purifier.

How Carbon Content is Calculated

In the test a signal will be obtained that is not attributable to the sample. The cause is a combination of impurities in the gas, crucible and accelerator. The average contribution to the carbon signal from these sources is determined to allow the sample contribution to be calculated. The inconsistency of impurity levels from these sources cannot be completely eliminated and this affects the ability to determine accurately to very low levels. As the method is relatively quick, repeat determinations are often requested to improve the accuracy of the determination (by taking the average of several results).

Source: LSM Analytical Services

For more information on this source please visit LSM Analytical Services