COD is a defined test; the extent of sample oxidation can be affected by digestion time, reagent
strength, and sample COD concentration.
COD often is used as a measurement of pollutants in wastewater and natural waters. Other
related analytical values are biochemical oxygen demand (BOD), total organic carbon (TOC),
and total oxygen demand (TOD). In many cases it is possible to correlate two or more of these
values for a given sample. BOD is a measure of oxygen consumed by microorganisms under
specific conditions; TOC is a measure of organic carbon in a sample; TOD is a measure of the
amount of oxygen consumed by all elements in a sample when complete (total) oxidation is
achieved.