Nano-level monitoring of Mn(2+) ion by fabrication of coated pyrolytic graphite electrode based on isonicotinohydrazide derivatives.

The two ionophores N'(N',N‴E,N',N‴E)-N',N‴-((((oxybis(ethane-2,1-diyl))bis(oxy)) bis(2,1-phenylene))bis(methanylylidene))di(isonicotinohydrazide) (I1) and (N',N‴E,N',N‴E)-N',N‴-(((propane-1,3-diylbis(oxy))bis(2,1-phenylene))bis(methanylylidene))di(isonicotinohydrazide) (I2) were synthesised and investigated as neutral carrier in the fabrication of Mn(2+) ion selective sensor. Several membranes were prepared by incorporating different plasticizers and anionic excluders and their effect on potentiometric response was studied. The best analytical performance was obtained with the electrode having a membrane of composition of I2: PVC: o-NPOE: NaTPB in the ratio of 6:34:58:2 (w/w, mg). Comparative studies of coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE) based on I2 reveal the superiority of CPGE. The CPGE exhibits wide working concentration range of 1.23×10(-8)-1.0×10(-1) mol L(-1) and a detection limit down to 4.78×10(-9) mol L(-1) with a Nernstian slope of 29.5±0.4 mV decade(-1) of activity. The sensor performs satisfactorily over a wide pH range (3.5-9.0) and exhibited a quick response time (9s). The sensor can work satisfactorily in water-acetonitrile and water-methanol mixtures. It can tolerate 30% acetonitrile and 20% methanol content in the mixtures. The sensor could be used for a period of four months without any significant divergence in performance. The sensor reflects its utility in the quantification of Mn(2+) ion in real samples and has been successfully employed as an indicator electrode in the potentiometric titration of Mn(2+) ion with ethylenediaminetetraacetic acid (EDTA).

Electroanalytical studies on Cu (II) ion-selective sensor of coated pyrolytic graphite electrodes based on N2S2O2 and N2S2O3 heterocyclic benzothiazol ligands.

Benzothiazol based chelating ionophores such as 1,3-bis[2-(1,3-benzothiazol-2-yl)-phenoxy]propane (L1) and 1,2'-bis[2-(1,3-benzothiazol-2-yl)-phenoxy]2-ethoxyethane(L2) were synthesized and explored as neutral ionophores in the fabrication of Cu(2+) ion-selective electrodes. Variety of PVC-based electrodes i.e., polymeric membrane electrodes (PME), coated graphite electrodes (CGE) and coated pyrolytic graphite electrodes (CPGE) were prepared. The membranes having composition L1:PVC:1-CN:NaTPB≡5:38:55:2 (w/w; mg) and L2:PVC:1-CN:NaTPB in the ratio of 6:39:53:2 are found to be exhibit the best potentiometric characteristics. The comparative studies of PME, CGE and CPGE based on L2 reveals that the CPGE is superior in terms of low detection limit of 6.30×10(-9) mol L(-1) with a Nernstian slope of 29.5 mV decade(-1) of activity between pH2.0 to 8.5 with a fast response time of 9s and could be used over a period of 5 months without any significant divergence in its potentiometric characteristics. The sensor has been employed for the estimation of Cu(2+) ion in real samples viz., water, soil and herbal medicinal plants and besides this, the sensor was also used as an indicator electrode in the potentiometric determination of Cu(2+) with EDTA.