Determination of Hg (II) in Food Specimens by a Straightforward Potentiometric Sensor Utilizing 5,12-dihydroquinoxalino(2,3-b)quinoxaline as the Ionophore

The research aimed to fabricate a coated graphite membrane electrode for the potentiometric measurement of mercury (II) using 5,12-dihydroquinoxalino(2,3-b)quinoxaline (L) as the ionophore. Density functional theory computations were employed to investigate the interaction of L with 10 different cations, revealing that L exhibited the strongest interaction with Hg (II). The optimized membrane entailed of 30% PVC, 9% L, 2% NaTPB, and 59% nitrobenzene (NB) yielded the best Nernstian response. The designed electrode revealed a broead linearity domain in the concentration range of 1×10-8-1×10-3 mol L-1 with a slope of 31.2±0.3 mV decade-1 and a limit of detection (LOD) of 7.5×10-9 mol L-1. Selectivity testing using the matched potential method showed no significant interference, affirming the sensor's selectivity. The electrode exhibited a rapid response time of 5 seconds and a lifespan of 4 months. Additionally, the potential response of the electrode remained unaffected by solution pH within the range of 3.0-8.0. The impact of organic solvents on the potential response was also evaluated, demonstrating that the sensor kept its Nernstian behavior in solutions with up to 20% non-aqueous content. In addition, the electrode was successfully utilized to determine Hg (II) in edible samples and employed as an indicator electrode in the potentiometric titration of Hg (II).