The Experimental Set-up
A proof of concept study was conducted by measuring the NIR spectra of a series of styrene / acrylonitrile / MEK samples of known concentration. A quantitative model was then developed using Partial Least Squares Regression (PLSR) which will allow the measurement of future samples based only on their NIR spectrum. A set of mixtures of known concentrations were analyzed with a Guided Wave NIR-O full spectrum analyzer using a 10 mm pathlength cell connected connected to the spectrometer via fiber optics. Guided Wave analyzer systems use fiber optics to allow the sample probe to be located in remote locations away from the spectrometer itself.
The Results
The NIR spectra of styrene, acrylonitrile, and MEK are shown in Figure 3. The mixture samples were used in Partial Least Square Regression (PLSR) models for each of the three components. The calibration results are summarized in Table 1 with predicted versus measured plots shown in Figures 4, 5, and 6. The NIR-O dual-beam spectrometer is an excellent choice for online, real-time measurements for hydrocarbon mixtures such as the one presented here.
The Conclusion
Real-time monitoring of polymer feed concentrations can be achieved with both Guided Wave analyzers; the NIR-O Full Spectrum NIR spectrometer or the ClearView db photometer. By collecting these data, process engineers in the polymer plant can make informed decisions on process optimizations to ensure product quality. The proof of concept study presented in this application note illustrates that Guided Wave process analyzers can detect changes in concentrations as little as 0.1 %wt. Contact us for more information.