A new Zn(II)-selective potentiometric sensor based on 4-tert-butylcalix[4]arene in PVC matrix

Area of Science:

• Electrochemistry
• Materials Science
• Analytical Chemistry

Background:

• Development of selective ion-sensors is crucial for environmental monitoring and industrial processes.
• Poly(vinyl chloride) (PVC) membranes are widely used in sensor fabrication due to their versatility.
• Calixarene derivatives have shown promise as ionophores in selective membrane sensors.

Purpose of the Study:

• To develop a new zinc-selective sensor using a PVC membrane.
• To investigate the performance characteristics of the developed sensor, including its selectivity, detection limit, and operational range.
• To evaluate the sensor's applicability in real-world samples, such as industrial wastewater.

Main Methods:

• Fabrication of PVC-based membranes incorporating 4-tert-butylcalix[4]arene (I) as the electroactive material, sodium tetraphenylborate (NaTPB) as an anion excluder, and tri-butylphosphate (TBP) as a plasticizer.
• Optimization of membrane composition through systematic variation of component ratios.
• Potentiometric measurements to determine the sensor's response characteristics, including working concentration range, slope, detection limit, pH range, response time, and operational stability.
• Selectivity studies against various interfering cations.
• Application of the sensor in potentiometric titration and analysis of industrial wastewater samples.

Main Results:

• The optimal membrane composition was found to be PVC: I: NaTPB: TBP in a 200:8:5:100 (w/w) ratio.
• The sensor exhibited a near-Nernstian slope of 28.0 ± 1.0 mV/decade over a wide concentration range (9.8 x 10⁻⁶ to 1.0 x 10⁻¹ mol dm⁻³).
• A low detection limit of 5.0 x 10⁻⁷ mol dm⁻³ was achieved, with a fast response time of 30 seconds and a stable response for over four months.
• The sensor demonstrated excellent selectivity for Zn(II) ions over other common cations and was successfully applied in potentiometric titrations and real sample analysis.

Conclusions:

• The developed PVC-based membrane sensor incorporating 4-tert-butylcalix[4]arene is highly selective and sensitive for zinc ion detection.
• The sensor's robust performance, including its wide working range, fast response, and long-term stability, makes it suitable for practical applications.
• This sensor offers a reliable and efficient tool for the determination of zinc ions in various matrices, including industrial wastewater.