New Type of Capacitive Detector for Determination of Ions

作者：Samphao Anchalee; Svegl Franc; Kalcher Kurt^*

来源：Asian Journal of Chemistry, 2011, 23(6): 2536-2542.

• Ion capacitive sensor
• Capacitive detector
• Transducer
• Capacitive sensor
• Ion-sensitive capacitor
• Ion detector

A new type of capacitive detector for the determination of ions was designed and fabricated. It consists of two thin layers of gold (thickness 24 nm) sputtered on a glass membrane (20 mm x 20 mm x 0.2 mm) as a dielectric. The upper metal layer of the capacitor had a circular gap (28 mm(2)) in the center as the sensing area. The capacitor was coupled with an inductor in parallel configuration to form a resonance circuit, whose frequency was determined. Solutions containing ions applied to the sensing area caused an increase in the I capacitance owing to an enhanced charge density on the sensing area. The upper limit of detection for ions was around 10(-3) mol dm(-3) of monovalent cations and anions. Higher concentrations did not produce higher capacitance. The lower detection limits were around 5 x 10(-5) mol dm-3. Studies were focused on the influence of the metal film thickness, size of the sensing area, response time, dynamic range, sensitivity, detection limit and long-term stability of the detector. The response was stable and reproducible for over 5 months. The signal responses were compared to conductivity measurements under flow injection conditions with standard solutions and mineral water samples. The results show a good correlation between both methods of measurement.

• 出版日期2011-6