Abstract
The performance of a novel ion-selective membrane electrode for the determination of mercury(II) based on a tribromomercurate-rhodamine B (TBM-RB) ion-pair complex has been described. The developed electrode showed a linear, reproducible, and stable potentiometric response with an anionic super-Nernstian slope of 69.5 ± 0.5 mV per decade over a wide range of concentration, 10
−5
-10
−2
M
, with a detection limit of 2.4 × 10
−6
M of Hg
2+
. The membrane showed a fast response time of 10-20 s and in a pH range of 1.5-7.5. The proposed sensor exhibited excellent selectivity for the tribromomercurate anion over anions: Br
−
, Cl
−
,
,
, acetate, oxalate, citrate, sulphate, phosphate, selenite, and nitrate. Also, there is a negligible interference from different cations such as, Ca
2+
, Sr
2+
, Cu
2+
, Ni
2+
, Co
2+
, Fe
2+
, Mn
2+
, Pb
2+
, Al
3+
, and Zn
2+
. The prepared sensor was used successfully as an indicator electrode for potentiometric titrations of mercury(II) with rhodamine B and thiosulphate. The analysis of mercury(II) ions in wastewater and microbial media with average recovery percentages of 100.6 ± 1.8% and 101.3 ± 1.7%, respectively, using the developed sensor was in good agreement with the data obtained using the standard dithiazone spectrophotometric method.