PO is a highly hazardous, flammable, and hygroscopic substance, and therefore needs to be handled with extreme caution. Tight control over moisture and other impurities in the final product (as well as along the manufacturing process at critical points) is necessary to overcome unwanted side reactions or poor yields. Manual laboratory methods can be quite cumbersome and can introduce bias depending on the analyst. Therefore, the hygroscopic nature of PO necessitates inline or online analysis of water content for the most precise results. Additionally, «real-time» analysis is a requisite for high throughput PO production because this gives short response times in case of process changes or increased water content in the final product. 

Safe analysis of low moisture content in PO is possible with reagent-free techniques such as near-infrared spectroscopy (NIRS). Suitable NIRS process analyzers are available for use in hazardous environments with robust stainless-steel flow cells (Figure 1). Metrohm NIRS process analyzers enable comparison of «real-time» spectral data from the process to the primary method (titration) to create a simple, yet indispensable model for the PO production process. Gain more control over production with a Metrohm Process Analytics NIRS XDS system configured for applications in hazardous areas, capable of monitoring up to 9 process points with the multiplexer option.

A reference method (i.e. KF titration) (Figure 2) is mandatory to build the prediction models. Measurements performed in the laboratory showed higher water content values than those predicted via online NIRS. By the time the KF titration was performed, the samples had captured atmospheric moisture and were no longer completely representative of the actual process conditions. Therefore, online KF titration was used to build more accurate prediction models.