The invention relates to a method for measuring concentration of low-concentration soluble organic
nitrogen in water, in which the nano
filtration membrane
separation technology is employed to accurately measure concentration of soluble organic
nitrogen. In the preparation process before pretreatment, membrane with a
pore diameter being more than or equal to 0.22mu m and less than or equal to 0.45mu m is employed to remove particle impurities of a
water sample.300-500mL of filtered
water sample is taken, pH value is adjusted to 6.0-9.0; in the process of pretreatment, selective nano
filtration membrane with a
cut-off molecular weight being 150-500 Dalton is adopted for dead-end or
cross flow filtration; so that 6-15 times of concentration and enrichment of DON in the
water sample can be achieved; the DON content is obtained by using the
total nitrogen to reduce other forms of
nitrogen content of other measurements and then dividing actual concentration times. In the invention,
accuracy and precision of DON measurement are greatly improved, so that the problems that negative values often appear in the direct water sample determination method and concentration standard deviation is large are solved; in addition, the whole measurement process of the measurement method is simple and effective, easy to operate, low in cost, so that the measurement method can be widely applied to
surface water and ground watermonitoring and monitoring and analysis of small, medium and large waterplants.