Oceanography

Principle

The water sample is allowed to react with molybdate under conditions which result in the formation of the conditions which result in the formation of the silicomolybdate, phosphomolybdate and arcenomolybdate complexes. A reducing solution, containing metal and oxalic acid is then added which reduces the silicomolybdate complex to give a blue reduction compound and simultaneously decomposes any phosphomolybdate or arcenomolybdate, so that interference from phosphate and arcenate is eliminated. The extinction of the resulting solution is measured at 810 nm.