Accurate quantification of dissolved organic nitrogen(DON) has been a challenge due to the cumulative analytical errors in the conventional method via subtracting dissolved inorganic nitrogen species(DIN) from total d...Accurate quantification of dissolved organic nitrogen(DON) has been a challenge due to the cumulative analytical errors in the conventional method via subtracting dissolved inorganic nitrogen species(DIN) from total dissolved nitrogen(TDN). Size exclusion chromatography coupled with an organic nitrogen detector(SEC-OND) has been developed as a direct method for quantification and characterization of DON. However, the applications of SECOND method still subject to poor separations between DON and DIN species and unsatisfied N recoveries of macromolecules. In this study, we packed a series of SEC columns with different lengths and resin materials for separation of different N species and designed an independent vacuum ultraviolet(VUV) oxidation device for complete oxidation converting N species to nitrate. To guarantee sufficient N recoveries, the operation conditions were optimized as oxidation time ≥ 30 min, injection mass(sample concentration × injection volume) < 1000 μL × mg-N/L for macromolecular proteins, and neutral p H mobile eluent. The dissolved O_(2)concentration in SEC mobile phase determined the upper limit of VUV oxidation at a specific oxidation time. Compared to conventional HW50S column(20 × 250 mm),HW40S column(20 × 350 mm) with mobile phase comprising of 1.5 g/L Na2HPO_(4)·2H_(2)O + 2.5g/L KH_(2)PO_(4)(p H = 6.85) could achieve a better separation of DON, nitrite, nitrate, and ammonia. When applied to river water, lake water, wastewater effluent, groundwater, and landfill leachate, the SEC-OND method could quantify DON as well as DIN species accurately and conveniently even the DIN/TDN ratio reached 0.98.展开更多
基金supported by the Basic Research Program of Jiangsu Province (No.BK20211557)the National Key R&D Program (No.2016YFE0112300)+1 种基金the National Natural Science Foundation of China (No.51708279)the High-level Talent Team Project of Quanzhou City (No. 2018CT006)。
文摘Accurate quantification of dissolved organic nitrogen(DON) has been a challenge due to the cumulative analytical errors in the conventional method via subtracting dissolved inorganic nitrogen species(DIN) from total dissolved nitrogen(TDN). Size exclusion chromatography coupled with an organic nitrogen detector(SEC-OND) has been developed as a direct method for quantification and characterization of DON. However, the applications of SECOND method still subject to poor separations between DON and DIN species and unsatisfied N recoveries of macromolecules. In this study, we packed a series of SEC columns with different lengths and resin materials for separation of different N species and designed an independent vacuum ultraviolet(VUV) oxidation device for complete oxidation converting N species to nitrate. To guarantee sufficient N recoveries, the operation conditions were optimized as oxidation time ≥ 30 min, injection mass(sample concentration × injection volume) < 1000 μL × mg-N/L for macromolecular proteins, and neutral p H mobile eluent. The dissolved O_(2)concentration in SEC mobile phase determined the upper limit of VUV oxidation at a specific oxidation time. Compared to conventional HW50S column(20 × 250 mm),HW40S column(20 × 350 mm) with mobile phase comprising of 1.5 g/L Na2HPO_(4)·2H_(2)O + 2.5g/L KH_(2)PO_(4)(p H = 6.85) could achieve a better separation of DON, nitrite, nitrate, and ammonia. When applied to river water, lake water, wastewater effluent, groundwater, and landfill leachate, the SEC-OND method could quantify DON as well as DIN species accurately and conveniently even the DIN/TDN ratio reached 0.98.
