Method for measuring total content of nitrogen of fresh water quality

The invention provides a method for measuring the total content of nitrogen of fresh water quality. The method comprises the steps of sampling, preparing an alkaline potassium persulfate solution, preparing a potassium nitrate standard solution, preparing a hydrochloric acid solution, drawing a calibration curve and detecting a water sample to be measured. According to the method, a polytetrafluoroethylene decomposition bottle is adopted to replace a colorimetric tube, so that the decomposition process is relatively sealed and relatively fully carried out, and the decomposition time is relatively short; cross contamination is not caused between the inside and the outside of the decomposition bottle, and interference is eliminated, so that the result is relatively accurate, and the operation is relatively simple and relatively convenient; furthermore, an opening or a plug of the colorimetric tube is prevented from being broken in the decomposition process, so that the problem of analyzing by sampling again is