Journal
ELECTROANALYSIS
Volume 28, Issue 12, Pages 2922-2929Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/elan.201600335
Keywords
Thiocyanate sensor; PVC electrode; salophen complexes; potentiometry
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Funding
- Cairo University
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New Mn(III)-L and Mn(IV)-L complexes were prepared from the highly lipophilic salophen ligand (L): phenol 2,2'-[(4,5-dimethyl-1,2-phenylene)bis[(E)-nitrilomethylidyne]]bis[4,6-bis(1,1-dimethylethyl). The prepared complexes were fully characterized and used for the construction of thiocyanate membrane electrodes. Optimized membrane electrodes contained 33.0 mg PVC, 66.0 mg o-nitrophenyloctylether, 50 or 5 (mole%) tetrakis(trifluoromethyl) phenyl borate and 1 mg Mn(III)-L (sensor 2) or Mn-(IV)-L (sensor 12), respectively. Such electrodes exhibited linear responses toward thiocynate in a concentration range of 10(-1)-10(-5) M and detection limits of 8.3 x 10(-6), 8.9 x 10(-6) M for sensor 2 and 12, respectively. Optimized membrane electrodes exhbited high selectivty toward thiocayante compared to more lipophilic anions. The observed thiocyanate selectivity of the optimized membranes was confirmed by formation constant calculations for Mn(III)-L and Mn(IV)-L with SCN-, beta=10(14.1) and 10(12.5), which was measured potentiometrically using the sandwich membrane method. Furthermore, computational study using DFT calculations was performed to at DFT/B3LYP level of theory to confirm the observed selectivity data. The response times were 3 and 0.5 min for low and high concentrations. The lifetimes of the optimized electrodes were similar to 4-6 weeks. The analytical utility of the optimized membrane electrodes was demonstrated by the analysis of thiocyanate level in different saliva samples.
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