The possibility of measuring the quality of the diesel engine exhaust fluid (DEF, AdBlue®) used in selective catalytic reduction (SCR) systems to reduce nitrogen oxide (NOx) emissions is the content of this work. There are two key motivations for quality measurement. Firstly, the quality of AdBlue® significantly influences the efficiency of SCR. Secondly, there are attempts to tamper DEF systems with water. DEF quality measurement is therefore required by regulations such as California Air Resources Board (CARB) or European emission standards (EURO 1-6). The quality of AdBlue® is affected by factors such as storage conditions, contamination and degradation. The results of AdBlue® quality measurements can be used to ensure optimal engine performance and minimize environmental impact. Several types of systems based on acoustic wave-based sensors, optical sensors, and others are used for measuring AdBlue® quality in vehicles. Impedance spectroscopy is a non-destructive technique used to study the electrical properties of materials over a wide range of frequencies. The technique has a high sensitivity and can provide valuable information about the properties of the varied materials. The thesis will deal with the possibilities of using impedance spectroscopy for measuring AdBlue® quality. The measurement will be performed on a unique cell that is in patent pending.