Nitrogenous compounds recalcitrant

Carbazole is a non-basic nitrogen compound, whose removal via hydrotreating is limited by its low reactivity. The removal of nitrogen by hydrotreatment involves a number of steps that take place on the catalyst surface. The weak interaction of neutral nitrogen compounds with catalysts precludes carbazole and its derivatives from being denitro-genated and makes them the most recalcitrant components in HDN of gas oils [308], In fact, it has been found that the nitrogen content of hydrotreated gas oil from Athabasca bitumen was composed primarily of alkyl carbazoles [309],... 

UV method was reported as an effective technique for the determination of the natural DON in seawater samples [56,80], even if some reference compounds containing N-N and N=N bonds were found clearly recalcitrant to UV oxidation. In contrast, [40] reported poorer recoveries of TDN in natural seawater samples and in reference materials by UV method compared to HTO and PO methods. The effectiveness of UV method was also controversially debated in the case of the analysis of nitrogen in rainwater samples and water-extracted aerosols [116-119]. Broad method comparisons of the different techniques for TDN analysis [148,151] showed that UV method can give comparable N-recoveries with respect to the other methods, although its precision seems to be lower, probably because of some uncertainties due to the colorimetric determination of the final inorganic nitrogen products. The low blank of this method and the possibility of the simultaneous determination of DON and DOP were cited as positive factors [40,80]. 

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