Synthesis of thiophene-2-carbaldehyde-(7-methyl-1,3-benzothiazol-2-yl)hydrazone and its application as an ionophore in the construction of a novel thulium(III) selective membrane sensor

Membrane sensors based on Schiff bases as chelating ionophores--a review

The development of chemical sensors has received widespread attention during the past two decades because of their extensive use in environmental monitoring and clinical analysis via rapid, accurate, reproducible, and low-cost methods. Chemically modified CPEs have frequently been employed as potentiometric sensors in trace analysis for metal ions, organic pollutants and biological substances. Most of these electrodes are operated via the ion-exchange process of the active component incorporated into the carbon paste matrix. This review article concentrates on such achievements in the context of the general development across the field. An overview of potentiometric sensors that are capable of detecting metal ions in environmental samples is presented and discussed. A survey on important advances in potentiometric sensors with regard to high selectivity, lower detection limit, and fast response time is presented in this review article.

Developments in the Field of Conducting and Non-conducting Polymer Based Potentiometric Membrane Sensors for Ions Over the Past Decade

Many research studies have been conducted on the use of conjugated polymers in the construction of chemical sensors including potentiometric, conductometric and amperometric sensors or biosensors over the last decade. The induction of conductivity on conjugated polymers by treating them with suitable oxidizing agents won Heeger, MacDiarmid and Shirakawa the 2000 Nobel Prize in Chemistry. Common conjugated polymers are poly(acetylene)s, poly(pyrrole)s, poly(thiophene)s, poly(terthiophene)s, poly(aniline)s, poly(fluorine)s, poly(3-alkylthiophene)s, polytetrathiafulvalenes, polynapthalenes, poly(p-phenylene sulfide), poly(p-phenylenevinylene)s, poly(3,4-ethylenedioxythiophene), polyparaphenylene, polyazulene, polyparaphenylene sulfide, polycarbazole and polydiaminonaphthalene. More than 60 sensors for inorganic cations and anions with different characteristics based on conducting polymers have been reported. There have also been reports on the application of non-conducting polymers (nCPs), i.e. PVC, in the construction of potentiometric membrane sensors for determination of more than 60 inorganic cations and anions. However, the leakage of ionophores from the membranes based on these polymers leads to relatively lower life times. In this article, we try to give an overview of Solid-Contact ISE (SCISE), Single-Piece ISE (SPISE), Conducting Polymer (CP)-Based, and also non-conducting polymer PVC-based ISEs for various ions which their difference is in the way of the polymer used with selective membrane. In SCISEs and SPISEs, the plasticized PVC containing the ionophore and ionic additives govern the selectivity behavior of the electrode and the conducting polymer is responsible of ion-to-electron transducer. However, in CPISEs, the conducting polymer layer is doped with a suitable ionophore which enhances the ion selectivity of the CP while its redox response has to be suppressed.

Schiff's Bases and Crown Ethers as Supramolecular Sensing Materials in the Construction of Potentiometric Membrane Sensors

Ionophore incorporated PVC membrane sensors are well-established analyticaltools routinely used for the selective and direct measurement of a wide variety of differentions in complex biological and environmental samples. Potentiometric sensors have someoutstanding advantages including simple design and operation, wide linear dynamic range,relatively fast response and rational selectivity. The vital component of such plasticizedPVC members is the ionophore involved, defining the selectivity of the electrodes' complexformation. Molecular recognition causes the formation of many different supramolecules.Different types of supramolecules, like calixarenes, cyclodextrins and podands, have beenused as a sensing material in the construction of ion selective sensors. Schiff's bases andcrown ethers, which feature prominently in supramolecular chemistry, can be used assensing materials in the construction of potentiometric ion selective electrodes. Up to now,more than 200 potentiometric membrane sensors for cations and anions based on Schiff's bases and crown ethers have been reported. In this review cation binding and anioncomplexes will be described. Liquid membrane sensors based on Schiff's bases and crownethers will then be discussed.

Lanthanide Recognition: an Asymetric Erbium Microsensor Based on a Hydrazone Derivative

N'-(2-hydroxy-1,2-diphenylethylidene)benzohydrazide (HDB) was found tohave a very selective and sensitive behavior towards erbium(III) ions, in comparison tothirteen lanthanide ions, inner transition and representative metal ions and was hence usedas a neutral ion carrier in construction of an Er(III) microelectrode. Theoretical calculationsand conductance studies of HDB to erbium and some other metal ions were carried out andconfirmed selectivity toward Er(III) ions.The best performance was obtained with a membrane contain 3% potassium tetrakis(p-chlorophenyl)borate (KTpClPB) as an anionic additive, 72% dibutyl phthalate (DBP) assolvent mediator, 5% HDB, and 20% poly(vinyl chloride) (PVC). The proposed Er(III)microelectrode exhibits a near Nernstian response of 17.5±0.5 mV per decade of erbiumactivity, and a very wide linear range 1.0×10-3-3.0×10-10 M. It can work well in the pHrange of 3.0-9.0. The lower detection limit (LDL) of the microelectrode was calculated tobe 2.0×10-10 M.