NOx & NO2 biosensor

dissolved nitrate & nitrite measurements


The Unisense Biosensor are advanced sensors for the measurement of nitrate and nitrite (NOx) in solution.

The biosensor is an excellent tool for on-line measurement in experiments where resolution of time and concentrations is important. The sensitivity is high and the sensor can measure concentrations below 0.5 µM. The NOx sensor has a good stability over days and works at full oceanic salinity.

Compared to conventional NO3 / NO2 analyzing systems (HPLC and ion chromatography) the Unisense NOx biosensor is a high quality research tool and a low cost alternative. The NOx biosensor can measure directly in soil slurries, drinking water, wastewater and water from lakes, streams and seas and it can be applied in a wide variety of research applications.

It is recommended that the Unisense Biosensor only be used indoors such as a lab or wastewater / treatment plant facility.


part numbers
  • NOx Biosensor – Macrosensor
  • NO2 Biosensor – Macrosensor
  • NOx Biochamber – Replaceable bioreaction chamber for nitrate
  • NO2 Biochamber – Replaceable bioreaction chamber for nitrite


detailed information

Unisense NOx-principle-900x450The biosensor consists of an electrochemical N2O transducer, equipped with a biochamber, which is mounted on the transducer by a simple locking ring. There are two versions of the bio chamber, one for nitrate/nitrite (NOx) measurements and one for nitrite (NO2) measurements.

The NOx or NO2 ions enter the sensor by molecular diffusion through the ion-permeable membrane. The active denitrifying bacteria reduce NOx or NO2 to N2O, which is detected electrochemically by the N2O transducer. The electron donors for this de-nitrification are contained in a nutrient reservoir within the sensor. The bacteria are therefore continually growing, making the biosensor much more robust than enzyme-based biosensors.
The electrochemical component (N2O transducer) and the biological component of the sensor are separated by a silicone membrane, which only allows gases to penetrate. Therefore, the only interfering substance is external N2O, which is normally present in negligible concentrations in natural environments.

This principle allows the sensor to measure NOx or only NO2 in chemically and biologically complex environments, e.g. seawater, waste water, liquid manure, mud, and soil extractions, without interference from substances other than N2O.



Bollmann,A. et al (2005), Influence of starvation on potential ammonia-oxidizing activity and amoA mRNA levels of Nitrosospira briensis, Applied and Environmental microbiology, 1276 – 1282, vol. 71

Juhler,S. et al (2009), Distribution and Rate of Microbial Processes in an Ammonia-Loaded Air Filter Biofilm, Applied and Environmental microbiology, 3705 – 3713, vol. 75



manual & docs

related products