Total nitrogen Lake Bidighinzu

The organic compounds containing nitrogen and phosphorus are simultaneously oxidized to nitrate and orthophosphate with the oxidizing mixture potassium persulfate, boric acid and sodium hydroxide; oxidation is simultaneous thanks to the variation between pH 9.7 and 5 obtained during oxidation by the boric acid - sodium hydroxide system. After oxidation, the total nitrogen is determined by direct reading of the nitrate at the wavelength of 220 nm, this determination is possible only on the oxidized sample because the oxidation disrupts the interfering organic compounds on the reading at 220 nm.