SCREEN-PRINTED VOLTAMMETRIC SENSORS FOR 2-FURALDEHYDE BASED ON NICKEL-MODIFIED AND AMALGAM-STABILIZED MERCURY-COATED CARBON INKS

This article describes a general method for stabilizing microdroplets of mercury on thick-film screen printed electrodes (SPEs). Electrodes modified with nickel metal powder are compared with amalgam stabilized mercury SPEs. Application of the electrodes to the measurement of org anic materials is demonstrated by the electrochemical determination of 2-furaldehyde, a marker for power transformer condition monitoring. T he electrodes were characterized by cyclic voltammetry and subsequentl y a square-wave voltammetric method was used to extend the detection l imit of the measurement. The resulting cathodic currents for the reduc tion of 2-furaldehyde was proportional to the concentration of 2-fural dehyde. Plots of 2-furaldehyde concentration against response at a nic kel-modified carbon SPE gave linear regions for concentrations in the range 3.7-14.3 ppm (regression equation; Y = 0.99 + 0.15x, r = 0.999, n = 3), and linear regions at mercury-coated silver-modified carbon SP Es in the range 8.9-36.4 ppm (regression equation; Y = 1.71 + 0.14x, r = 0.999, n = 3) and in the range 0.9-8.9 ppm (regression equation; Y = 1.34 + 0.17x, r = 0.980, n = 3), respectively. A particular advantag e of using the mercury-modified SPE rather than the nickel-modified ba se card is that the well-defined electrochemistry of furan derivatives allow them to be individually distinguished. The half-wave potentials at the mercury SPE for 2-furaldehyde (E-1/2 = -1.15 V vs Ag/AgCl) and two possible interferents 2-acetyl-furan and 5-methyl-2-furaldehyde ( E-1/2 = -12 and -1.31 V vs. Ag/AgCl) are sufficiently well separated t o allow the individual components to be resolved whereas at a nickel-m odified SPE a combined signal is observed.