AMPEROMETRIC DETERMINATION OF N-NITROSAMINES IN AQUEOUS-SOLUTION AT AN ELECTRODE COATED WITH A RUTHENIUM-BASED INORGANIC POLYMER

The diffusion-limited electrochemical oxidation of N-nitrosamines in an aqueous pH 1.5 buffer is demonstrated at a glassy carbon electrode which is coated with a film of mixed valent ruthenium oxides that are stabilized by cyano crosslinks (mvRuCN). The process occurs at 1.080 V vs Ag/AgCl, 3 M NaCl where Ru(VI) is the electron-transfer mediator in the film. The mvRuCN electrode was used in a potentiostatic amperometric detector for flow injection analysis and highperformance liquid chromatography to allow the determination of representative compounds such as N-nitrosodimethylamine, N-nitrosodi-n-propylamine (NNDPA), and N-nitrosodiphenylamine (NNDPhA). Using HPLC with a C-18 column, a linear least squares calibration curve for NNDPA over the range 5.0 x 10(-8) to 1.0 X 10(-6) M (8 points) had a slope of 12.8 +/- 0.2 nA/mu M and a correlation coefficient of 0.999; the detection limit (signal equal to three times the noise) was 10 nM. The relative standard deviation of five replicate injections of 0.80 mu M NNDPhA was 2%. A pooled relative standard deviation over a 22-day period (15 sets, five trials per set) of 2% documents long-term stability.