With an ATR-probe For the UV-vis range it is possible to apply spectrophotometry to very concentrated process liquors without dilution. In this paper the application of a new ATR-probe to the monitoring of sulfur species during an electrochemical process for production of polysulfides is presented. In this system, the temperature and the total salt concentration are relatively constant. A linear relation exists between the ATR-probe response and the concentration of adsorbing species. Therefore, the process can be followed by simple monitoring of a few wavelengths. The ATR-probe was easily implemented and showed no signs of deterioration in the hot strongly alkaline medium. Temperature has a significant effect on measurement with ATR-probes. Other factors that might also affect the measurements using an ATR-probe an briefly discussed.