| Title | Influence of nitrogen speciation on the TDN measurement in fresh waters by high temperature catalytic oxidation and persulfate digestion |
| Abstract | Analytical methodologies for the determination of total dissolved nitrogen (TDN) in waters are based on a conversion step able to transform selectively all the nitrogen species into a compound that is then quantified. A crucial requirement to meet accuracy is the quantitative recovery of all organic and inorganic nitrogen species during the conversion step. In this work, the N recoveries of two widely employed methodologies that use different conversion steps (high temperature catalytic oxidation (HTCO) and persulfate digestion (PD)) were assessed on a set of organic nitrogen compounds, representative of the structures of both dissolved organic matter (DOM) and anthropogenic contaminants. Low recoveries are due to poor selectivity during the conversion step, with the formation of nitrogen compounds other than nitrogen oxide (HTCO) and nitrate (PD). The results show that in many instances the TDN measurements give systematically low results depending on N speciation. PD could give lower results than HTCO even for samples containing only DOM of biological origin. In particular (i) low N recovery was always observed with compounds having two or more contiguous N atoms; (ii) the HTCO method is very effective for TDN quantification in the presence of s-triazine rings while PD method did not yield satisfactory N recovery; (iii) a full N recovery was observed with compounds having amido or amino groups or nitrogen atoms in imidazole, indole and pyrimidine rings; and (iv) the N recoveries for purine derivatives are almost complete with HTCO, but give systematically low results by PD. Finally, the estimation of dissolved organic nitrogen (DON) fluxes and pools from TDN measurements can be affected by uncertainties larger than previously thought as a consequence of (i) the lower N recovery for some nitrogen compounds and (ii) the differences in the N recovery as a function of the adopted analytical methods. |
| Source | International journal of environmental analytical chemistry 96 (5), pp. 474–489 |
| Keywords | Total dissolved nitrogendissolved organic nitrogenhigh temperature catalytic oxidationpersulfate oxidationtotal organic carbonDON/DIN recovery |
| Journal | International journal of environmental analytical chemistry |
| Editor | Gordon and Breach., New York,, Stati Uniti d'America |
| Year | 2016 |
| Type | Articolo in rivista |
| DOI | 10.1080/03067319.2016.1150467 |
| Authors | Minella, M.; Tartari, G. A.; Rogora, M.; Frigione, M.; Vione, D.; Minero, C.; Maurino, V. |
| Text | 381406 2016 10.1080/03067319.2016.1150467 ISI Web of Science WOS 000375012000005 Total dissolved nitrogen dissolved organic nitrogen high temperature catalytic oxidation persulfate oxidation total organic carbon DON/DIN recovery Influence of nitrogen speciation on the TDN measurement in fresh waters by high temperature catalytic oxidation and persulfate digestion Minella, M.; Tartari, G. A.; Rogora, M.; Frigione, M.; Vione, D.; Minero, C.; Maurino, V. Department of Chemistry and NIS Centre of Excellence, University of Torino, Torino Italy; CNR Institute of Ecosystem Study, Verbania Pallanza, Italy; Centro Interdipartimentale NatRisk, University of Torino, Grugliasco TO, Italy Analytical methodologies for the determination of total dissolved nitrogen TDN in waters are based on a conversion step able to transform selectively all the nitrogen species into a compound that is then quantified. A crucial requirement to meet accuracy is the quantitative recovery of all organic and inorganic nitrogen species during the conversion step. In this work, the N recoveries of two widely employed methodologies that use different conversion steps high temperature catalytic oxidation HTCO and persulfate digestion PD were assessed on a set of organic nitrogen compounds, representative of the structures of both dissolved organic matter DOM and anthropogenic contaminants. Low recoveries are due to poor selectivity during the conversion step, with the formation of nitrogen compounds other than nitrogen oxide HTCO and nitrate PD . The results show that in many instances the TDN measurements give systematically low results depending on N speciation. PD could give lower results than HTCO even for samples containing only DOM of biological origin. In particular i low N recovery was always observed with compounds having two or more contiguous N atoms; ii the HTCO method is very effective for TDN quantification in the presence of s triazine rings while PD method did not yield satisfactory N recovery; iii a full N recovery was observed with compounds having amido or amino groups or nitrogen atoms in imidazole, indole and pyrimidine rings; and iv the N recoveries for purine derivatives are almost complete with HTCO, but give systematically low results by PD. Finally, the estimation of dissolved organic nitrogen DON fluxes and pools from TDN measurements can be affected by uncertainties larger than previously thought as a consequence of i the lower N recovery for some nitrogen compounds and ii the differences in the N recovery as a function of the adopted analytical methods. 96 Published version Articolo in rivista Gordon and Breach. 0306 7319 International journal of environmental analytical chemistry. International journal of environmental analytical chemistry International journal of environmental analytical chemistry Int. j. environ. anal. chem. michela.rogora ROGORA MICHELA gabriele.tartari TARTARI GABRIELE |
