Potentiometric determination of mercury(II) using a tribromomercurate-rhodamine BPVC membrane sensor

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 x 10(-6) M of Hg2+ . 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- SCN42- CrO42- acetate, oxalate, citrate, sulphate, phosphate, selenite, and nitrate. Also, there is a negligible interference from different cations such as, Ca2+, Sr2+, Cu2+, Ni2+ , Co2+, Fe2+, Mn2+, Pb2+, Al3+, and Zn2+ . 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.