CONICET | Buscador de Institutos y Recursos Humanos

Nitrogen, phosphate and silicon are the main nutrient limiting and stimulating the planktonic primary production. Phosphate can vary from nanomolar to micromolar levels in ocean waters. However, oligotrophic systems are characterized for having nanomolar concentrations of phosphate, nitrogen and silicon. The northern Adriatic Sea is a particular water system, in which the levels of nutrients are commonly low or unbalanced with an abundance of nitrogen inflow both from rivers and water runoff being probably behind several eutrophication events previously reported. Laboratory methods and classical analytical equipment can be used to detect nutrient levels (in particular phosphate) with high precision and sensitivity, however, they are expensive, time cost and lack in portability. So there is a great need to develop analytical systems or new methods to detect nitrate, phosphate and silicon in oligotrophic seawaters as early diagnosis and in-field of the quality of the sea water. In general, phosphate detection can be done with the classical molybdenum-blue method. However, the method cannot be used in oligotrophic seawater samples due to its low sensitivity and high interference problems. Electrochemical methods are often proposed for in field detection to overcome some of the drawbacks as turbidity of the sample and optical interferences. In this study, we present a new method, characterized by the advantage of both simplicity and low cost, based on the application of a plastic conductive electrode containing a molybdenum reagent embedded. The original non-conventional electrode was characterized by surface electron microscopy, energy dispersive X-ray analysis and electrochemical methods. The sensitivity obtained for phosphate detection was high enough to detect this nutrient in oligotrophic seawater systems.