Abstract: A monitoring system configured to receive an on-line sample associated with a process includes a sample chamber positioned to receive the on-line sample and a detector positioned to selectively receive and detect multiple wavelengths of light transmitted through the sample during an absorbance measurement, and emitted by the sample during a fluorescence measurement in response to illumination by each of the at least one excitation wavelength. An optical fiber couples light transmitted through the sample and directs the transmitted light to the multi-channel detector during the absorbance measurement. Optics direct light emitted by the sample during the fluorescence measurement to the detector without passing through any optical fiber. A computer in communication with the detector is configured to correct the fluorescence measurement using the absorbance measurement and determine a sample parameter based on the fluorescence and absorbance measurements of the on-line sample.