Triazine is one of the most commonly used scavengers for removal of hydrogen sulphide in the offshore oil and gas industry, but the kinetics of the scavenging reactions are still poorly understood. In this work the feasibility of Raman spectroscopy for on-line monitoring of the aqueous phase reaction between 1,3,5-tri-(2-hydroxyethyl)- hexahydro-s-triazine (HET) and HS- was studied. It was found that the development of specific peaks in the Raman spectra reveals clear patterns related to the changes of concentration of HET and HS- with time. On this basis, a qualitative evaluation of the dependence of the reaction kinetics on temperature and pH was carried out. No change in Raman peaks was observed at 40 °C for reaction time of 30 minutes, but a reaction was observed at 50 °C. Furthermore, a decrease in the reaction rate as the initial pH increases was observed in the pH range 8.5 to 10.3. No change in peaks was observed at pH 10.3 within 30 minutes.