I get lower results for nitrate on samples containing salt with the cadmium reduction method. What can I do about this?
Cadmium reduction for nitrate in seawater samples
Chloride in the sample at levels greater than 100 mg/L slows the reaction with the NitraVer5 and NitraVer6 reagents. The best solution is to calibrate the instrument using nitrate standards that have been spiked with chloride to the same level as the samples, or switch to a different analysis method. Some nitrate methods include details how to create a calibration curve with the chloride matrix.