Widespread acceptance of Raman spectroscopy in chemical process monitoring requires instrument calibration, which is automated, repeatable, reliable, verifiable, and transferable from instrument to instrument. Key elements to be calibrated in a dispersive Raman analyzer are Raman emission wavelengths, the spectral response of the instrument, and the excitation laser wavelength. Modern Raman instruments are capable of simultaneously monitoring multiple sample points in a process pipeline. In a typical industrial installation, multiple remote probe heads are coupled to a central instrument (laser source, spectrograph, CCD detector and control/software) via fiber optic cables up to hundreds of meters in length. Instruments must self- calibrate and validate without direct access to remote probe head installations. The presence of a holographic laser notch filter in the system presents unique calibration challenges. The implications of these issues on instrument configuration and calibration/ validation protocol are discussed. Candidate wavelength and intensity calibration references are compared. Examples of industrial Raman applications and their requirements on calibration accuracy and precision are given.
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