Tracking AdBlue properties during tests of selective catalytic reduction (SCR) systems ‐ the suitability of various analytical methods for urea content determination

Abstract

Summary Reliability tests of selective catalytic reduction (SCR) systems are performed extensively in industry. The aim of this work was to track the AdBlue properties when testing SCR systems under enhanced temperatures (around 80 °C). To extend and improve the current practice in the automotive industry, HPLC and titration were chosen to develop and optimize appropriate analytical methods for urea content determination in various AdBlue samples. We showed that the testing (temperature loading) of SCR systems is associated with changes of the properties of AdBlue such as conductivity, alkalinity, density, urea content and absorbance. Our results demonstrate the unsuitability of refractometry as a method for tracking urea concentration in AdBlue during tests of SCR systems. HPLC and titration proved to be accurate and precise methods to determine urea in untreated as well as in treated AdBlue samples. Both analytical methods are not affected by matrix effects – accuracy ranged from 96.6% to 100.0% and precision ranged from 0.18% to 3.24%. We showed that the process of testing SCR system is associated with changes of properties of AdBlue such as conductivity, alkalinity, density, urea content and absorbance. Our results provide compelling evidence of the necessity to extend the list of possible methods to determine the urea content in AdBlue given by ISO 22241‐2 for the automotive industry. HPLC and titration were proved as accurate and precise methods for urea concentration determination.