Combustion Analysis

Introduction

Combustion analysis is a powerful technique for obtaining the elemental composition of organic and inorganic materials. Laboratory analyzers can provide susceptible and reliable Carbon, hydrogen, oxygen, nitrogen, and sulfur measurements. This technique is critical in various domains, including chemistry, environmental science, pharmaceuticals, and materials science, where precisely identifying these components is required to understand material characteristics, quality control, and standard compliance.

Scope

Combustion analysis is mainly focused on measuring elemental quantification and also helps calculate the empirical or molecular formula of organic compounds. It additionally helps in quality control and environmental monitoring. 

Principle and Procedure

Principle:

The principle behind the combustion analysis is to burn the sample at a high temperature in excess of oxygen, which causes complete combustion of the sample. During the combustion process, Carbon is oxidized to Carbon dioxide, hydrogen is oxidized to water, etc.

Total organic Carbon (TOC) and total inorganic Carbon (TIC) are also measured after sample acidification. The operating temperature could be as high as 3000 °C and vary depending on the furnace. The infrared cells are customized based on the type of analyzer. Combustion analysis done in testing labs can detect concentrations of C/S and O/N/H as low as one ppm. Combustion analysis is a highly reliable technique for elemental analysis of solid samples, especially at low concentrations.

Procedure:

How to do combustion analysis?

Sample Preparation:The sample will be in solid form, precisely weighed, and placed in a combustion chamber.

Combustion: The sample is burned in a stream of pure oxygen at high temperatures, typically around 900–1000°C.

Gas Collection and Analysis:

• The gases produced during combustion (CO₂, H₂O, N₂, SO₂) are passed through a series of detectors or absorbents.
• The amount of each gas is measured using thermal conductivity detectors, infrared spectroscopy, CHNS/O Analyzers, Elemental Analyzers, etc., calibrated to give the amount of the corresponding element.

Combustion Analysis Formula:

Mass of Carbon from CO₂:

Mass of Carbon = Mass of CO x {molar mass of carbon / molar mass of CO₂}

The Mass of Hydrogen from H₂O:

Mass of hydrogen = mass of H₂O X {molar mass of carbon / molar mass of CO₂}

The Mass of oxygen

Mass of Oxygen=Total Mass of Compound−(Mass of Carbon+Mass of Hydrogen)

Protocol

Emissions: The process generates gases like CO₂, SO₂, and NOx, which must be appropriately vented or scrubbed to avoid environmental contamination.

Sample Handling: Proper handling of the sample and calibration standards is essential to ensure accuracy and prevent contamination.

Sample Size:

The sample size necessary for combustion analysis varies based on the individual substance being examined, the sensitivity of the instrument, and the precision required.

Result 

Results are presented as weight percentages of each element (C, H, N, S, and O).

The data is used to calculate the compound’s empirical formula or to confirm that the material meets its specification, for instance, in fuel analysis or organic compound synthesis. 

Analysis of natural gas combustion products

Analyzing natural gas combustion products allows us to evaluate combustion efficiency, fuel consumption, and pollutant emissions. Complete combustion generates CO₂ and H₂O, but incomplete combustion can result in hazardous pollutants such as CO, unburned hydrocarbons, and NOx. Analytical techniques such as gas chromatography, IR spectroscopy, and chemical sensors are widely employed to quantify these compounds.

Advantages and Limitations

The following are some of the advantages and limitations of combustion analysis:

Applications

• Precise measurement of C/S/N/H/O concentrations in bulk, powders, granules, or other solid samples
• Test inhomogeneous samples
• Check carbon impurities in materials
• Fractional analysis
• Total organic and total inorganic carbon measurements (TOC and TIC)
• The total, accessible, and bound carbon content for ceramics
• The surface carbon content of metals and alloys

Conclusions

Combustion analysis is a potent technique for identifying the elemental composition of organic molecules and materials, giving critical information for quality control, environmental monitoring, and scientific study.

FAQs