Determination of total nitrogen in natural waters by means of persulfate oxidation

The amount of total nitrogen in unpolluted waters will rarely exceed 5 - 30 μg.at.N/ liter. The determination of such amounts by a procedure applicable to routine analysis presents great difficulties, and the ultraviolet light oxidation method is recommended if at all possible. For those laboratories where this equipment is not available a direct chemical approach may still be necessary. Strickland and Parsons, in their "A Practical Handbook of Seawater Analysis" (1968), have combined a micro Kjeldahl treatment with a determination of the resulting ammonia according to Richards and Kletsch (1964), however, a Kjeldahl digestion is not a routine procedure, especially for ship-board use.
At the Council Meeting last year the author presented a paper on the determination of total phosphorus in natural waters by means of persulfate oxidation (C.M. 1968 / C:33, Hydrography C.). That method has been used successfully at several institutes and on board research vessels. As organically bond phosphorus can be oxidized one can assume that nitrogen of organic substances can be oxidized with persulfate also. That this is the case will be shown in this paper.