Potential of Fourier transform infrared spectroscopy and fiber optics for process control

Fourier transform infrared (FT-IR) spectroscopy is well-established as an off-line analytical technique. In this work, the spectrometer is adapted through the addition of an optical fiber system to provide a powerful tool for on-line analysis and control. A multiplexed fiber interface has been constructed, enabling rapid sequential analysis of up to six different samples. Novel fiber optic sampling cells developed for the system include a transmission cell for use in the near-infrared (near-IR) and an attenuated total reflectance (ATR) cell for the mid-infrared (mid-IR). A number of commercially available optical fibers with varying transmission properties have been investigated. High-quality spectra have been acquired from a variety of food samples and calibrations obtained for components such as carbohydrates and ethanol in soft and alcoholic drinks. A prototype process control system uses the calibration data to control simple processes such as additions and dilutions.