Abstract
Poly vinylchloride (PVC) based membranes of 4,4',4'',4'''-21H,23H-porphine–5,10,15,20 –tetrayl) tetrakis (benzoic acid) (TBAP) and 2,3,7,8,12,13,17,18-octamethyl - 21H, 23H-porphine (OMP) were prepared using dibutyl phthalate (DBP), dioctylphthalate (DOP), dibutyl(butyl)phosphonate (DBBP) and 1-chloronaphthalene (CN) as plastcizing solvent mediators and sodium tetraphenylborate (NaTPB) as an anion excluder for Ni2+ selective sensors. TBAP based membrane exhibits linearity over a wide concentration range 2.0x10-6–1.0x10-1M (0.12 – 5.8x103ppm) with a slope of 29.6 mV/decade of activity while OMP based membrane showed linear potential response in the concentration range 1.0x10-5 –1.0x 10-1M (0.60 – 5.8x103ppm) with a Nernstian slope of 29.0 mV/decade of activity. The electrode assembly works between pH 2.0 – 7.0, exhibits a fast response time of 10-15s and performed satisfactorily over a period of six months with good reproducibility. Excellent selectivity of the order of 10-3 over a number of cations and quantitative determination of Ni2+ in effluents discharged from electroplating industry demonstrates the utility of the proposed sensor. The electrode assembly was also used as an indicator electrode in the potentiometric titration of Ni2+ with EDTA.
Highlights
Utility of chemical sensors responding selectively to a specific ion in diverse samples viz. soils, industrial effluents, pharmaceutical compounds, clinical analyses etc. is well established
The potential response of all the membrane sensors was studied in the concentration range 1.0x10-6–1.0x10-1M Ni2+ (Figs.1 & 2)
TBAP based membrane electrode No.1 exhibited linearity in the concentration range 5.0x10-5–1.0x10-1M with a slope of 26.0 mV/decade of activity while the membrane consisting of OMP as electroactive ingredient showed a linearity in the concentration range 1.0 x 10-4 – 1.0 x 10-1 M with a slope of 32.4 mV/decede of activity
Summary
Utility of chemical sensors responding selectively to a specific ion in diverse samples viz. soils, industrial effluents, pharmaceutical compounds, clinical analyses etc. is well established. In continuation of our work on the development of selective nickel-sensor [14,15,16], the use of carboxylated and methylated porphines as active constituents for the membranes has been investigated and the results are presented .
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