Neutral-carrier-based ion-selective electrodes

Crown ether-based structures for sensitive electrochemical detection

N-(2-Hydroxypropyl)methacrylamide-co- N-acryloxysuccinimide with 2-aminomethyl-18-crown-6 (p(HPMA-NAS-18C6)) graft copolymer deposited on the gold (Au) electrode is able to bind heavy metal cations from aqueous solutions. The binding of the lead(II) cations (Pb2+) is monitored by quartz crystal microbalance, cyclic voltammetry, and anodic stripping voltammetry. Electrochemical studies have demonstrated that the presence of p(HPMA-NAS-18C8) on the Au electrode surface resulted in the shift of Pb oxidation wave to less negative potentials, accompanied by the increase of the oxidation peak magnitude. The p(HPMA-NAS-18C6)-modified electrode could sensitively detect Pb2+ cations in a range from 10 ppb to 4.39 ppm with a low detection limit of 0.17 ppb.

Ion-specific nutrient management in closed systems: the necessity for ion-selective sensors in terrestrial and space-based agriculture and water management systems

The ability to monitor and control plant nutrient ions in fertigation solutions, on an ion-specific basis, is critical to the future of controlled environment agriculture crop production, be it in traditional terrestrial settings (e.g., greenhouse crop production) or as a component of bioregenerative life support systems for long duration space exploration. Several technologies are currently available that can provide the required measurement of ion-specific activities in solution. The greenhouse sector has invested in research examining the potential of a number of these technologies to meet the industry's demanding requirements, and although no ideal solution yet exists for on-line measurement, growers do utilize technologies such as high-performance liquid chromatography to provide off-line measurements. An analogous situation exists on the International Space Station where, technological solutions are sought, but currently on-orbit water quality monitoring is considerably restricted. This paper examines the specific advantages that on-line ion-selective sensors could provide to plant production systems both terrestrially and when utilized in space-based biological life support systems and how similar technologies could be applied to nominal on-orbit water quality monitoring. A historical development and technical review of the various ion-selective monitoring technologies is provided.

The synthesis of (N2O2S2)-Schiff base ligands and investigation of their ion extraction capability from aqueous media

Two new Schiff bases (I) and (II) containing nitrogen-sulfur-oxygen donor atoms were designed and synthesized in a multi-step reaction sequence. The Schiff base (I) was used in solvent extraction of metal chlorides such as Cu2+ and Cr3+ as well as metal picrates such as Hg2+ and UO2(2+) from aqueous phase to the organic phase. The influences of the parameter functions, such as pH, solvent, ionic strength of aqueous phase, aqueous to organic phase and concentration of the extractant were investigated to shed light on their chemical extracting properties upon the extractability of metal ions. The effect of chloroform, dichloromethane and nitrobenzene as organic solvents over the metal chlorides extraction was investigated at 25±0.1 °C by using flame atomic absorption and the result is that the ability of extraction in solvents as follows: C6H5NO2>CHCl3>CH2Cl2 and the compositions of the extracted species have been determined. The metal picrate extraction was investigated at 25±0.1 °C by using UV-visible spectrometry. As well that the extraction of picrates metal such as UO2(2+) and Hg2+ with Schiff base(I) in absence and presence of 2-(2-aminoethyl) pyridine was investigated in chloroform. The extraction results revealed the presence of neutral donors 2-(2-aminoethyl) pyridine shifts the extraction percentage curves towards higher pH region, indicating a synergistic effect of this donors on extraction of UO2(2+) and Hg2+ by the studied Schiff base (I).

Highly selective optical fluoride ion sensor with submicromolar detection limit based on aluminum(III) octaethylporphyrin in thin polymeric film

A highly selective, sensitive, and reversible fluoride optical sensing film based on aluminum(III)octaethylporphyrin as a fluoride ionophore and a lipophilic pH indicator as the optical transducer is described. The fluoride optical sensing films exhibit a submicromolar detection limit and high discrimination for fluoride over several lipophilic anions such as nitrate, perchlorate, and thiocyanate.