VOLTAMMETRIC BEHAVIOR AND ION-CHROMATOGRAPHIC DETECTION OF NITRITE ATA DISPERSED PLATINUM GLASSY-CARBON ELECTRODE

Cyclic voltammetry was used to investigate the electrochemical behavio r of nitrite at a platinum-modified glassy carbon electrode (Pt-CME) i n phosphate buffer (pH 4.5). Experiments in flow injection analysis an d ion-chromatography (IC) were performed to characterize the electrode as an amperometric sensor for the determination of nitrite ions. The effects of several common interferences on the amperometric signal wer e estimated. The electrode stability, precision, limit of detection, a nd linear range were evaluated at a constant applied potential of 1.1 V. Calibration plots were linear from 0.03 mu M to 0.5 mM with a slope of about 21 mu A/mM and a correlation coefficient of 0.9987. The limi t of detection (LOD) was 15 nM (0.7 ppb) in a 100 mu L injection. The electrode response was sufficiently stable: over 6 h of operating time a 2.8 % signal loss was observed. The determination of nitrite in mil k and pear juices was achieved by IC and the relevant results were com pared with those obtained with a standard spectrophotometric method.