| Summary: | 碩士 === 國立成功大學 === 化學工程學系 === 86 === Ammonium ion sensor has a great deal of interest due to its
importance in analyzing ammonium ion in many areas, such as
foods, drugs, biochemical studies and environmental pollution
controls. In this study, chemical redox, T-T, chemical oxidizing
and electropolymerization by constant potential methods were
used to prepare Pt/Nafion?Pt、Au/Nafion恣BPpy/Nafion?Ppy、
PAni/Nafion?Pani and Ppy/Pt/Nafion?Pt electrodes of two-
electrode type. The better sensing electrode of all methods is
Pt/Nafion?Pt electrode prepared by chemical redox method.The
optimal conditions of preparing Pt/Nafion?Pt electrode was
using 0.01M Pt salt, impregnating 40 minutes, temperature 40℃of
the water bath and applying ultrasonic agitation, then using
0.2M BaBH4 as reducer, pH 13, reacting 30 minutes and applying
ultrasonic agitation. After reaction, the electrode was
impregnated in 0.01M H2SO4 for 1 hour to exchange H+ ion.The
best sensing conditions are at temperature 40℃, flow rate
0.1072 ml/sec and pumping 10 minutes. The sense in limit is
0.00001M ammonium ion and corresponds a 23.7 nA sensing current.
The diffusion control was proposed in this study. Based on the
theory and results show that a square form of NH4+ inlets
concentration, the relation between sensing current and NH4+
concentration is ( 1
)where the diffusitivity of the ammonium ion in effective
diffusion layer is 1.33×10-8 cm2/sec. But for a step of change
NH4+ concentration and the time approaches infinite, the
relation between limit current and NH4+ concentration is
( 2 ) The linear relationship of Ilim and CNH4+ was
experimentally conformed and the diffusion layer Le was
5.5×10-4 cm.The ammonium ion sensor in this study was
interfered by both nitrate ion and chloride ion which have
strong negative electric charge strength. And the acetate ion
would moderately degrade the sensing current of the ammonium ion
sensor.
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