Urea plays a vital role in amino-acid and protein metabolism, enabling 80-90% of nitrogen excretion from the human body. It is generated in the liver in the urea cycle, transported via the bloodstream, and excreted into the urine by the kidneys . For this reason, measuring urea level in urine and/or blood is routinely used medical diagnostic technique to evaluate liver and kidney function . Moreover, [ 13 C]-urea and [ 13 C, 15 N 2 ]-urea have recently become attractive contrast agents for hyperpolarized magnetic resonance imaging studies, making the compounds a valuable marker for the evaluation of myocardial perfusion and renal physiology . Finally, the interest in urea is also stimulated by a growing demand for robust and reliable instrumentation for compound detection in such fields as environmental monitoring as well as agricultural and food chemistry .