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

摘要

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) (I_1) and (N',N'"E,N',N'"E)-N',N'"-( ((propane-1,3-diylbis(oxy))-bis(2,1-phenylene))bis(methanylylidene))di(isonicotinohydrazide) (I_2) 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 I_2: 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 I_2 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 (9 s). 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).