Patent ID: 8269192

Claim:
An apparatus for quantitatively measuring the amount of optical brighteners in a selected water sample, the apparatus comprising: a. a chamber where the selected sample is exposed to ultraviolet excitation at a wavelength of about 300 to 400 nm; b. one or more fluorometers that measure raw fluorescence emission from the selected sample at a first emission wavelength of about 400 to 500 nm and at a second emission wavelength of about 500 to 600 nm; c. one or more electronic computational devices that: i. correct raw fluorescence emission measurements from the selected sample for sample absorption at the excitation wavelength and first and second emission wavelengths using measured, modeled or both measured and modeled absorption coefficients to provide absorption-corrected fluorescence emission values for the selected sample at the first and second emission wavelengths; ii. determine the ratio of the absorption-corrected fluorescence emission value at the first emission wavelength to the absorption-corrected fluorescence emission value at the second emission wavelength for a comparison water sample in which optical brighteners are not present or are only minimally present; iii. use such ratio and the absorption-corrected fluorescence emission value for the selected sample at the second emission wavelength to determine the expected or background absorption-corrected fluorescence emission value for the selected sample at the first emission wavelength; and iv. determine the amount of optical brighteners in the selected sample by subtracting the expected or background absorption-corrected fluorescence emission value for the selected sample at the first emission wavelength from the absorption-corrected fluorescence emission value for the selected sample at the first emission wavelength.