Macherey Nagel has recently launched a new Quantofix test for Nitrate which measure below 100ppm.
This simple test is suitable for a range of applications including the detection of nitrate content in whey.

This test strip is for the fast and reliable determination of nitrate in whey and aqueous solutions. The easy Dip & Read procedure provides a reliable result within 60 seconds.
In the cheese dairy saltpeter -Potassium Nitrate is often added to inhibit the growth of micro organisms. The nitrate ions have a high solubility in water and remain in the resulting whey. Before this is further processed to food supplements it has to be removed. To avoid health risks, the concentration of nitrate has to be monitored regularly. Also some vegetables can contain high amounts of nitrate that has to be controlled.
The full range of Quantofix test strips and other Macherey Nagel rapid tests are available from the camlab website.