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The nitrite-selective PVC membrane electrodes prepared with lipophilic long-chain tetraal-kyltin compounds as neutral carrier show selectivity patterns significantly different from those obtainedwith classical anion-exchangers. The potentiometric selectivity coefficient for nitrite ion with respectto nitrate ion has been improved by about four orders of magnitude. The linear response range ofthe electrode based on tetralauryltin (TLT) is from 1×10~(-1)M down to 2×10~(-5)M with a detectionlimit of 5×10~(-6)M. The Nernstian response of the electrode in the medium of pH≥7 graduallychanges to a doubled super-Nernstian response when the solution turns slightly acidic. The changeof the response slope has a closely relation with the stepwise complex-formation equilibrium of thecarrier with the anion involved, which was experimentally studied by using ultraviolet spectroscopy.An explanation of the anomalous response behavior as well as the curve form of the potential-pHplot is given.
The nitrite-selective PVC membrane electrodes prepared with lipophilic long-chain tetraal-kyltin compounds as neutral carrier show selectivity patterns significantly different from those obtained with classical anion-exchangers. The potentiometric selectivity coefficient for nitrite ion with respectto nitrate ion has been improved by about four orders of magnitude. The linear response range of the electrode based on tetralauryltin (TLT) is from 1 × 10 -1 M down to 2 × 10 -5 M with a detection limit of 5 × 10 -6 M. The Nernstian response of the electrode in the medium of pH ≥ 7 graduallychanges to a doubled super-Nernstian response when the solution turns slightly acidic. The changeof the response slope has a closely relation with the stepwise complex-formation equilibrium of thecarrier with the anion involved, which was experimentally studied by using ultraviolet spectroscopy. An explanation of the anomalous response behavior as well as the curve form of the potential-pHplot is given.