LaMotte SMART Spectro Spectrophotometer - Manual (Page 115)

INTERFERENCES: Volatile organic compounds are not oxidized to the extent
that they are in the vapor above the digestion solution.
Therefore, they do not contribute to the COD reading.
Contains mercury sulfate to prevent interference from
chloride. Nitrite gives a positive interference of 1.1 ppm O
2
per ppm NO
2
–N, which is insignificant unless nitrite
concentrations are very high. Other reduced inorganic
compounds are stoichiometrically oxidized, causing a positive
interference. Corrections can be made for these compounds
based upon their stoichiometry and concentrations.
COD–HR 2/4 SMART SPECTRO TEST PROCEDURES 03.05