Kinetic determination of urea in serum by stopped-flow spectrophotometry

The determination of urea based on its reaction with biacetyl in the presence of thiosemicarbazide and iron(III) has been studied kinetically by using a modular stopped-flow system. This study gave some new data about this coloured reaction and led to the development of a simple, fast method which overcomes some of the disadvantages (e.g., long analysis times, high temperatures and acid concentrations) of the conventional equilibrium method for the determination of urea, which hinder its application to routine analyses. The linear range (0.5–15 μg ml^?1), detection limit, precision and selectivity of the proposed kinetic stopped-flow method are reported. The method has been satisfactorily applied to the analysis of serum samples without pretreatment. The results correlate well with those obtained by the urease method.