Patent ID: 7372039

Claim:
A UV absorption spectrometer comprising: a housing, a controller, and a sensor unit including an ultraviolet light source, an analytical area in an analytical cell or in running water or gaseous medium, and an UV wavelength separator including a UV detector, wherein an ultraviolet light in a wavelength range of 200-320 nm emits from the light source through the analytical area to the wavelength separator, and the controller transforms output signals from the UV detector into absorbance values or optical densities for two or more wavelengths in the wavelength range, calculates differences of said absorbance values or optical densities, determines a concentration of a chemical in the solution with calibration constants found for a known concentration of the chemical and said differences of said absorbance values or optical densities, wherein the UV wavelength separator includes at least one optical filter comprising an interference filter having a thin transparent spacer placed between two semi-reflective coatings so as to use multiple reflections and interference to select a narrow frequency band.