| Research Abstract |
We have been studied phosphate-, perchlorate-, mercury-, thiocianate-ions-selec-tive electrode and their electrode were applied to the routin analysis.
In this report, we have determined potentically Tl ^+ selectivivity of the ion selective electrode with plasticized PVC membrane containing 1,4,7,10,13,16-hexathiacyclooctadecane (HTCO). Membrane plasticized tin-selective electrode with 1,4,7-trithianonane (TTCN) and silver-selecctive electrode with neutral carriers (HTCO and 1,10-diaza-4,7,13,16-tetrathiaoctadecane (ATCO)) were developed.
The effect of the membrane matrix, eg. amount of ionic additivity [(lipophilic salt , potassium tetrakis (p-chlorophenyl) borate (KTpcClPB)] and different plasticizer (dioctyl phtalate, DOP ; dioctyl sebacate, DOS ; 2-nitrophenyl octhylether (NPOE) on these electrodes and the selectivities have been investigated in detail.
The produced membrane electrodes with good performanece and optimum response are as follows : Thallium (I) electrode : HTCO : 2.0w/w%
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, PVC : 28.0w/w%, DOP : 68w/w%, KTpClPB : 2.0w/w% ; Tin (II) electrode : TTCN : 3.0w/w%, PVC : 75/08w/w%, DOP : 21.17w/w%, KTpClPB : 0.75w/w% ; Silver (I) electrode : HTCO : 1.52w/w%, PVC : 22.94w/w%, DOP : 74.71w/w%, KTpClPB : 0.823w/w% ; ATCO : 1.67w/w%, PVC : 22/85w/w%, DOP : 74.53w/w%, KTpClPB : 0.943w/w%.
Selectivities of above described electrodes were determined the mixed-solution, the sigle-solution and the continuous-variation methods. For example, the results of the continuous-variation method are as follows : The decreasing order of selectivities are Fe^<3+>>Co^<2+>, Ni^<2+>, Cr^<3+>>Mn^<2+>, Cd^<2+>, Mg^<2+>>Ba^<2+>, Zn^<2+>, Pb^<2+>>NH_4^+, K^+, Na^+>Li^+ (thallium(I)electrode) ; Bi^<3+>>Ca^<2+>>Pb^<2+>, Zn^<2+>>Fe^<3+>>Co^<2+>>Cu^<2+>>Na^+ (tin(II) electrode) ; Hg^<2+>, Mg^<2+>>Ni^<2+>>Zn^<2+>>Ca^<2+>, Mn^<2+>>Co^<2+>>Ce^<3+>>Fe^<3+>>Cr^<3+> (silver(I) electrode with HTCO) ; Hg^<2+>>Mg^<2+>>Ni^<2+>>Mn^<2+>, Zn^<2+>>Ca^<2+>>Co^<2+>>Cr^<3+>, Ce^<3+>>Fe^<3+> (silver(I) electrode with ATCO).
It is found that the interference ion with high electric charge does not affected on peformance of these electrode, while soft metal ions do. To investigate the ion exchange and complexation mechanism in membrane electrode with neutral carriers the impedace spectra was discussed. Bulk resistance of the membrane, the double layr capacitances, electric current dencity of charge transfer, diffusion coefficients in the membrane and Warburg coefficient were evaluated by the analysis of the cole-cole plot with two half circle. The relationship between the potentiometrically selectivity and exchange current dencity ratio was consisted. Less
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