An amperometric sensor based on ionic liquid and carbon nanotube modified composite electrode for the determination of nitrite in milk

A novel carbon composite electrode has been fabricated using ionic liquid n-octylpyridinum hexafluorophosphate (OPFP) and single-walled carbon nanotube (SWCNT). This electrode combined the advantages of ionic liquid and SWCNT as well as the characteristics of the “bulk” composite electrodes. Compared with the commercial glassy carbon electrode (GCE) and the ionic liquid–graphite (IL-G) composite electrode, the ionic liquid–SWCNT (IL-SWCNT) composite electrode exhibited remarkable increase in the electron transfer rate for electroactive compound and significant decrease in the overpotential for the oxidation of nitrite. Based on the enhanced electrocatalytic activity for the oxidation of nitrite, a wide linear range from 1.0 μM to 12.0 mM with a low detection limit of 0.1 μM was obtained. Furthermore, the IL-SWCNT electrode was applied to determine nitrite levels in milk samples. Experimental results showed that the proposed electrode could be used as an effective and sensitive sensor for the determination of nitrite.