Analysis of total dissolved nitrogen in natural waters by on-line photooxidation and flow injection

Flow injection analysis as a tool for enhancing oceanographic nutrient measurements—A review

“…In batch digestion methods the digestion period is sufficiently long (hours) that peroxydisulphate oxidant is completely converted to sulphuric acid [150], whereas in automated methods the UV or thermal exposure time required for complete oxidation of N-species is short (10s of seconds) and there remains a high residual concentration of peroxydisulphate which can potentially damage the reduction column. For example, McKelvie et al [151] used UV photo-oxidation with alkaline peroxydisulphate to completely convert dissolved N species to nitrate which was detected by spectrophotometry after Cd-reduction and diazotization. To avoid degradation of the Cd column by continuous contact with the high concentration of S 2 O 8 2− required to achieve complete digestion, photo-oxidation was performed in a separate sub-manifold, and only a small volume of digested sample was injected into the detection sub-manifold.…”

Analytical Aspects of Amino, Quaternary Ammonium, Nitro, Nitroso and Related Functional Groups

“…See reaction 14 in Section IV.D.3.g for analogous processess of color development. Compounds 260, 261 and 263 were determined in various matrices: In formulations, feed and milk by RP-HPLC-UVD 537 or using a high-speed C 18 3 ð 3 column 538 , and in animal tissues by RP-LC on a ODS Hypersil column 539 ; in foods of animal origin by extraction with acetonitrile, followed by TLC or HPLC 540 . 260 and 261 were determined in shrimp muscle tissue by LC 541 .…”

Investigations on Ozone-Based and UV/US-Assisted Synergistic Digestion Methods for the Determination of Total Dissolved Nitrogen in Waters

“…This approach does not need expensive instruments, is easy to implement, and can be employed for simultaneous determination of total nitrogen and total phosphorus [18][19][20]. During the last 25 years, some published procedures using alkaline persulfate include batch mode [21] and flow analysis methods [22][23][24][25] with both thermal and UV radiation assisted digestion [26,27]. Flow analysis methods with UV mineralization allow high sample throughput, but the limited digestion time may result in partial conversion with interference of unreacted persulfate on the Cd/Cu column which is commonly employed in nitrate analyzers.…”