When a Sulfur containing sample is combusted at 1000 ℃, Sulfur dioxide (SO2) is formed: R-S + O2 –> SO2 + H2O + CO2

The amount of Total Sulfur present in the sample is measured by pulsed UV-Fluorescence detection technique. Applying this detection technique together with oxidative combustion of the sample proceeds as follows:
Sulfur dioxide (SO2) is formed during high temperature oxidation and transferred to a reaction chamber. Here it is excited by a pulsed UV source and as the excited state is unstable, the excited SO2 instantly decays to its ground state energy level. During this process, UV light is emitted. As this light has a different wavelength than the original UV source, the Photomultiplier tube is able to detect this emission.

The amount of light emitted reflects the total amount of SO2 present in the combusted sample, which is directly related to the amount of Total Sulfur present in the sample.

The equations for this reaction are:
SO2 + hv1 –> SO2*
SO*2 –> SO2 + hv2

TSHR makes use of auto gain-controlled UV-Fluorescence detector principle which results into automatic correction of UV-light intensity and so avoid UV-lamp calibration procedures.