This application note gives a complete solution for determining the biuret content in Adblue® diesel exhaust liquid by measuring the absorbance of urea-copper complex using METTLER TOLEDO UV Vis spectrophotometer.
Role of AdBlue Diesel
On combustion of diesel, the automobile engine extensively releases nitric oxide gases (NOx) into atmosphere. NOx has an adverse impact on environment causing smog formation, acid rains or depletion of ozone layer in the atmosphere. Reducing the level of NOx in the atmosphere is of utmost importance. One of the methods to minimise the release of NOx is by reducing it into nitrogen and water through the combustion process. Such reactions demand a catalyst and urea is quite an effective one for the above mentioned reduction process. Urea solution in water (AUS 32) is sprayed into the exhaust tank for reducing the NOx gases. This urea solution is termed as AdBlue® globally.
The biuret content corelates to the urea concentration in AUS32 solutions (ISO22241-2, Annex C).
How to Evaluate the Biuret Content?
Biuret forms a blue colored complex with copper(II) ions when sample is added into the aqueous copper sulfate solution. Inorder to maintain the alkaline condition, sodium potassium tartarte is added. Absorbance values of this blue colored complex measured at 550 nm using UV Vis spectrophotometer can be used to evaluate the concentration of biuret.
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