Nutrients can be categorized as primary or trace. Primary nutrients are those needed in relatively high concentrations while trace nutrients are those needed in relatively low concentrations. Trace nutrients include metals such as iron and copper. The primary anions are those generally found in greatest concentration. Chloride, bicarbonate, and carbonate are the other primary anions found in surface and ground waters.
Organic nitrogen includes nitrogen in organic molecules such as amino acids.
In this method all organic compounds are oxidized using boiling sulfuric acid and a catalyst such as mercuric ion. The nitrogen is released as ammonium. The older methods are colorimetric. A yellowish brown color develops when Nessler's reagent is added while an intense blue color develops when the phenol solution is added. Color or turbidity in the sample can interfere with both colorimeteric methods.