New method for urea analysis in surface and tap waters with LC-OCD-OND (liquid chromatography–organic carbon detection–organic nitrogen detection)

A new method for urea detection in surface and tap waters using LC-OCD-OND was developed. It could be shown that urea, ammonia and nitrate could be separated chromatographically from each other and from NOM (natural organic matter). A direct quantification at its specific retention time is possible using custom-made detectors for nitrogen and for organic carbon. Further, urea can be detected indirectly as urea is transformed to ammonia after enzymatic hydrolysis with urease. After sufficient contact time for complete hydrolysis to ammonia (about 320 minutes) urea concentration can be calculated on the basis of the additional ammonia measured by LC-OCD-OND. The limit of detection of urea as mass was determined as 4 ppb for natural waters and 1 ppb for deionised waters.