Ion-Selective Electrodes for Mercury Determination at Low Concentrations: Construction, Optimization and Application

Abstract

Potentiometric studies are presented here on solid contact ion-selective electrodes, based on neutral carriers comprising structural sulfur−donating groups and an aliphatic chain, where the latter confers stability to the molecule for the formation of metal complexes. As result, an ISE was obtained for the potentiometric determination of mercury. This sensor allowed continuous mercury determinations at nanomolar levels within a wide concentration interval (1.0 × 10 −9 to 1.0 × 10 −1 ) molL −1 , with a detection limit of (9.1 ± 0.8) × 10 −10 molL −1 and a Nernstian response of (29.8 ± 0.4) mV decade −1 . This ISE can be used in the 0-6 pH interval, exhibiting a high selectivity toward the mercury ions even in the presence of interferents, and be used as an indicating electrode during potentiometric mercury titration with EDTA, because it is comparable with the commercial electrodes, within its same class. The main advantage of the ISE reported here is its nM LOD and that it does not require an internal reference.

Potentiometric Sensing

“…Juarez-Gomez et al presented a new Hg 2+ ionophore, O , O ′-(2,2′-biphenylene)­dithiophosphate methyl . An ISE based on this neutral carrier exhibited a Nernstian response of 29.8 mV and an attractive detection limit of 9.1 × 10 –10 M. While the authors demonstrated a stable potential in the pH range from 0 to 6.0, they chose rather surprisingly an extreme pH of 0 as being optimal for further measurements.…”

“…With cation-sensitive sensors, the selectivity was significantly improved with porphyrin dimers instead of single porphyrin molecules. The selectivity coefficient values depended on the order of porphyrin units in the dimer.These interesting discoveries will likely stimulate the application of complex porphyrin systems with more than one porphyrin units.Juarez-Gomez et al presented a new Hg 2+ ionophore, O,O'-(2,2'biphenylene)dithiophosphate methyl 107. An ISE based on this neutral carrier exhibited a Nernstian response of 29.8 mV and an attractive detection limit of 9.1•10 -10 M. While the authors demonstrated a stable potential in the pH range from 0 to 6.0, they chose rather surprisingly an extreme pH of 0 as being optimal for further measurements.…”

Determination of total mercury in seafood by ion-selective electrodes based on a thiol functionalized ionic liquid

“…As can be seen from Fig. 4 , the electrode sensitivity keeps constant when the conditioning time is above 2 h. The conditioning time of the reported Hg 2+ -selective electrodes is 24 h [ 11 ]. That is to say, short conditioning time is one of the advantages of the proposed sensors.…”

“…After digestion and cooling, the digestion solution was diluted to 25 mL with water. Before measurements, the digestion solutions were pretreated according to the reported works [ 11 – 13 ]: 5.0 mL of a specific digestion solution was taken and its pH was adjusted to 3.0 with NaOH solution (1.0 mol L −1 ); finally, this solution was diluted to 50 mL with HNO 3 solution of pH 3.0. Blank experiments were carried out in a similar way.…”

Design and Characterization of Electrochemical Sensor for the Determination of Mercury(II) Ion in Real Samples Based upon a New Schiff Base Derivative as an Ionophore

“…Many organic and inorganic compounds have been documented in the literature as ionophores for the synthesis of ion selective electrodes for the determination of Hg 2+ ion in various samples over the last three decades. Crown ether derivatives [19,20], polyvinyl pyridine [21], calix [4]pyrrole amide derivative [22], calixarene derivatives [23][24][25][26][27][28], thiol functionalized ionic liquid [29], amines [30,31], thioureas [25,32], and dithio derivatives [33,34] have all been used as ionophores for designing ISEs of Hg 2+ ions. It's worth mentioning that, some ionic liquids, e.g., 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF 4 ) [35], polypyrrole (PPy) [36], O,O -(2,2 -biphenylene)dithiophosphatepentyl (PenDTF) [37], 1methyl-2-butylthioimidazolium combined with bis(trifluoromethanesulphonyl) imide [29], dimethylglyoxime [38], and 2-mercaptobenzimidazol (2MBI) [39] are widely employed as ionophores in ISEs of Hg(II) ions.…”