DETERMINATION OF UREA AND ITS THERMAL-DECOMPOSITION PRODUCTS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

The thermal decomposition of urea can yield a wide variety of products; apart from ammonia and isocyanic acid, addition compounds of higher molecular mass may appear. In order to detect their presence in exhaust gases from a selective catalytic reduction (SCR) process using urea as a reducing agent, a chromatographic method was developed. The chromatographic separation is performed on an anion-exchange column using a phosphate buffer (pH 7) as eluent and UV detection at 190 nm. The method allows the simultaneous determination of neutral compounds (urea, biuret, melamine, ammeline) and of anions (cyanurate, isocyanate, acetate, formate, nitrite, nitrate, etc.). The value of the method for optimizing urea-SCR process design is illustrated.