Nitrosamines electrochemical detectors

The development in the determination of many classes of nonvolatile nitrosamines depends on the development of detectors suitable for the trace analysis of ionizable, ionic, macromolecular, and thermally unstable A-nitroso compounds. In particular, the development of detectors compatible with reversed-phase liquid chromatographic conditions is receiving special attention. Among others, the electrochemical detectors are attractive because of their high sensitivity and their ability to operate in different aqueous and mixed aqueous-organic eluents. 

Although GC/MS techniques remain the basic hallmark of analysis for pesticides and their derivatives, it is important to stress the need and the specific role of additional methodologies such as thermal energy analysis and electrochemical detectors. The former technique was discussed with particular emphasis on its utility of the determination of trace levels of nitrosamines and nitrosated pesticides in agricultural products and residues. 

The diffusion-limited electrochemical oxidation of V-nitrosamines in an aqueous pH 1.5 buffer was demonstrated at a GCE coated with a film of mixed valence ruthenium oxides, stabilized by cyano crosslinks. This electrode was used in a potentiostatic amperometric detector for FIA and HPLC, to allow the determination of representative N-nitrosamines (278a, 278c and 278d) for 278c, LOD was 10 nM and RSD 2% at 0.80 pM... 

Some interesting classes of nitrosamines are decomposable by warm strong acids or by photolytic cleavage in alkaline media so that nitrite or nitrous acid is produced. They can be electrochemically detected as such or after further reaction. The availability of a voltametric detector for flowing solutions equipped with solid electrodes allows the direct anodic detection of the NO2 species produced by postcolumn photolysis. The Ce(IV) and iodide in acid medium have been investigated as postcolumn reagents for the oxidation and voltametric detection of the nitrite produced by the warm acid decomposition of nonvolatile nitrosamines. 

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