Development of a new experimental automatic method for the determination of dissolved urea in seawater

Urea is an important component of nitrogen cycling in the marine environment, being it excreted by marine mammals, fishes and zooplankton and taken up by several plankton species. Anthropogenic inputs of urea are common in the coastal zones, in particular due to the load of continental waters and to the atmospheric deposition. However, scarce information is still available on this nitrogen compound, mainly because of the lack of robust analytical methods for its determination in seawater. The most reliable technique for urea determination is colorimetry, based on the chemical reaction with diacetyl monoxime. However, this reaction requires hard experimental conditions that make problematic its automation. Since 2004, a new automatic flow-segmented method for urea determination has been developed in the laboratory of the CNR Marine Science Institute of Trieste, which has significant upgrades compared to other existing analyzers. This method was published on the scientific literature and used in several oceanographic studies included in research projects.