[robert.cook]

does anyone know of an accurate and reliable way to determine the concentration of nitrates in sulfuric acid? i am in the process of creating a new procedure for my company and would like any suggestions

[Archer]

You could try using the oxidised nitrogen method for water (see ref). I can't see why this couldn't be adapted for sulfuric acid, depending on what your limit of quantification needs are.

The nitrate is reduced to nitrite by a hydrazine-copper reagent. The nitrite then reacts with sulphanilamide and another compound to form a azo dye. This can then be quantified by UV/Vis.

The only downside is that this test picks up any nitrite already present too, you would need to run the test without the reducing agent if you needed to differenciate the two oxidation states of nitrogen.

Ref
Oxidised Nitrogen in Waters, 1981, HMSO, ISBN 0 11 751593 0