What is Loss on Ignition (LOI)?

Loss on Ignition is a method used within inorganic analytical chemistry. The practice consists of ‘igniting’ (vigorous heating) a sample at a designated temperature which enables volatile substances within the sample material to escape, until the mass of the sample ceases to change. This process is often performed within air but may be done in another inert or reactive atmosphere.

What does Loss on Ignition measure?

Loss on Ignition measures the organic matter content in samples such as soil, cement, sludge, and waste. The volatile materials which are lost during the analysis typically consist of combined water (hydrates, for example) and CO₂ from carbonates. It can be used as a quality test and ensures volatile organic matter have been removed from a sample.²

The Loss on Ignition is the amount of weight lost in the sample once it has gone through the heating process.³

Loss on Ignition Calculation

Loss on Ignition of a sample is reported as an elemental or oxide analysis of a mineral.  It is calculated by comparing the weight of a sample before and after it has been subjected to the high temperatures during ignition. The Loss on Ignition calculation represents the amount of organic matter that was in the sample.⁴

Loss on Ignition Method: How to Perform Loss on Ignition

A common method of how to perform LOI is as follows:

• An empty crucible is weighed and recorded before adding the sample
• A sample is placed into the crucible and the crucible is weighed again. The sample weight is determined by deducting the empty crucible weight from the new weight.
• The sample is then placed into the drying oven as required to dry the sample material
• Once cool, the crucible is re-weighed (the difference gives the sample water content)
• The muffle furnace is then set to the desired temperature and the sample is ignited for the necessary length of time
• Once cool, the crucible is weighed again. The difference between this weight and the dry weight gives the organic content. ²

Loss on Ignition Soil Testing: What Does Loss on Ignition Tell You About Soil?

Soil is composed of minerals, living organisms, water, and more organic matter. Soil productivity is influenced by the organic matter content.  In agricultural soil, a high organic matter helps to improve the water holding capacity, improves the ability of the soil to withstand pH changes and provides sustenance for living organisms in the soil. Therefore, monitoring the soil organic matter can help direct soil management practises in agriculture and so using Loss on Ignition to determine soil’s organic matter mass is a useful procedure.

Determining the moisture content of soil is also an important process. Discover more on the topic in our previous article: Measuring Soil Moisture Content using the Gravimetric Method.

Loss on Ignition Test Equipment from Precisa

For Loss on Ignition Tests Precisa’s prepASH is the perfect fit. The prepASH by Precisa combines high performance, ease of operation, precision, and integrity of measurement to maximise time and accuracy. It determines moisture and ash values automatically and produces up to 80% savings in workload and costs. In one working cycle, up to 29 specimens and a reference are automatically ashed, monitored and recorded within a wide temperature range of 50° to 1000°C.

Find out how Precisa’s prepASH performs during a Loss on Ignition test in this application note where the prepASH is used to determine the LOI on Petrochemical Catalysts:

• Application Note: Thermogravimetry for the Determination of the Loss on Ignition on Petrochemical Catalysts

View our Series 340 EM prepASH Thermogravimetric Analyser and enquire today for more information.

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References

1. https://www.carbolite-gero.com/applications/heating-applications/loi-lod-tga/#:~:text=LOI%20%2F%20LOD%20%2F%20TGA-,Loss%20on%20Ignition%20(LOI),to%20burn%20or%20to%20volatilise.
2. https://en.wikipedia.org/wiki/Loss_on_ignition
3. https://www.cemnet.com/Articles/story/160205/loss-on-ignition.html
4. https://www.sfu.ca/geog/soils/lab_documents/Estimation_Of_Organic_Matter_By_LOI.pdf#:~:text=Loss%20on%20Ignition%20%28LOI%29%20analysis%20is%20used%20to,chemicals%2C%20only%20the%20use%20of%20a%20muffle%20furnace