The Thermo Scientific™ Model 450i analyzer operates on the principle that H2S can be converted to SO2. As the SO2 molecules absorb ultraviolet (UV) light and become excited at one wavelength, the molecules then decay to a lower energy state emitting UV light at a different wavelength.
Specifically: The pulsing of the UV source lamp serves to increase the optical intensity whereby a greater UV energy throughput and lower detectable SO2 concentration are realized. Reflective bandpass filters, as compared H2S -> SO2 SO2 + hv 1 -> SO2* -> SO2 + hv2 to commonly used transmission filters, are less subject to photochemical degradation and are more selective in wavelength isolation. This results in both increased detection specificity and long term stability.
