Highly sensitive determination of nitrite using FMWCNTs-conducting polymer composite modified electrode

Nitrite is detected in 0.2 M phosphate buffer solution at pH 7.2 using a glassy carbon (GC) electrode modified with a nanostructured composite. The composite consists of 5-amino-1,3,4-thiadiazole-2-thiol (ATT) electrochemically deposited on acid functionalized multiwalled carbon nanotubes (FMWCNTs). After the deposition of p-ATT film on the FMWCNTs, SEM images reveal that components segregate and the diameter of the FMWCNTs increases from 58 to 139 nm. The oxidation peak potential for nitrite oxidation on the FMWCNTs-ATT polymer (p-ATT) composite-modified GC electrode shifts to a less positive potential and the accompanying oxidation current is two-fold greater compared to the nitrite oxidation at bare GC electrode. Further, nitrite is selectively oxidized at the composite modified GC electrode in the presence of 3300-fold excess of common interferents like sodium fluoride, sodium nitrate, calcium chloride, magnesium sulphate, potassium carbonate, calcium carbonate and zinc sulphate. The amperometric current response for nitrite oxidation linearly increases with the concentration of nitrite from 10 to 1000 nM. The limit of detection was found to be 0.2 nM (S/N = 3). Finally, the practical application of the present method was demonstrated by determining nitrite in milk samples.