Elemental Microanalysis technique

On this page, we explain the technique used by the Elemental Microanalysis Service at the University of Sheffield's Department of Chemistry.

About this facility

Technique 1Sample Preparation

Samples are accurately weighed out on a 5 point balance, before being sealed within a tin capsule for analysis.We work with small samples of around 1.5 - 2 mg but can deal with larger samples if required, for example if the sample is not homogeneous. We ask for 10 mg of sample per analysis (or more if larger samples are to be analysed).

Vario MICRO cube CHN/S analyser

Technique 2

The Elementar vario MICRO cube is capable of analysing for the percent of carbon, hydrogen, nitrogen and sulphur. Samples are catalytically combusted and reduced, producing N2, CO2, H2O and SO2. These gases are captured by an adsorption tube and then released in turn by increases in the temperature of the adsorption tube. The gases are detected using a thermal conductivity detector, the signal is integrated and the % of each element is calculated. Blanks and daily factors are used to ensure consistency between different runs, and standards are run at regular intervals to check the function of the analyser.

We work to a tolerance of ± 0.3 % and our limit of detection is 0.3%, although if you wish to analyse for levels below this then that can be discussed.

Schöniger flask combustion

Technique 3

The analysis of Br, Cl and I can be done using the Schöniger flask combustion method. The sample accurately weighed sample is combusted in a hermetically sealed oxygen enriched environment, where upon total decomposition the resultant gases are absorbed in solution and a titration is used to determine the amount of the compounds as a percentage of the total sample. As with the CHN/S analysis, we work to a tolerance of ± 0.3 % and our limit of detection is 0.3%, and we ask for 10 mg of sample per analysis.