Method for testing total nitrogen by using flow injection analyzer and application thereof

The invention relates to a method for testing total nitrogen by using a flow injection analyzer, which is used for testing on the basis of the flow injection analyzer, and comprises the steps of (1) under the irradiation of ultraviolet light, adding a digestion solution into a water sample to be tested, and heating to obtain a digestion product A; (2) adding a buffer solution into the digestion product A, and reducing to obtain a reduction product B; (3) adding a color developing agent into the reduction product B to obtain a to-be-detected substance C; and (4) measuring the absorbance value of the to-be-measured substance C, and calculating the corresponding total nitrogen concentration. Solutes of the buffer solution comprise acid, ammonia water and a metal chelating agent, so that ammonia nitrogen in the to-be-detected water sample can be prevented from escaping in the form of ammonia gas, the interference of metal ions and acid-base degree in the to-be-detected water sample on thetest accuracy is reduced,