Novel bilirubin-based PVC calcium sensors

Area of Science:

• Analytical Chemistry
• Electrochemistry
• Materials Science

Background:

• Development of selective ion-selective electrodes (ISEs) is crucial for accurate chemical analysis.
• Poly(vinyl chloride) (PVC) based membranes are widely used for ISE construction.
• Bilirubin has been explored as a potential neutral carrier for metal ion detection.

Purpose of the Study:

• To construct and characterize PVC membrane sensors for Ca(II) ions using bilirubin as a neutral carrier.
• To evaluate the performance of different plasticizers on sensor selectivity and sensitivity.
• To assess the sensor's applicability in real-world sample analysis.

Main Methods:

• Fabrication of PVC membrane sensors incorporating bilirubin and various plasticizers (o-nitrophenyloctyl ether, dioctyl phthalate, dibutyl sebacate).
• Investigation of plasticizer effects, anionic excluder, pH, and foreign ion interference.
• Potentiometric measurements using the separate solution method for selectivity coefficient determination.
• Calibration using varying Ca(II) concentrations to establish Nernstian response and detection limits.

Main Results:

• The sensor with o-nitrophenyloctyl ether as a plasticizer exhibited superior selectivity for Ca(II) ions, even in the presence of high concentrations of alkali and alkaline earth metals.
• A linear Nernstian response (29.5 ± 0.8 mV/decade) was observed for Ca(II) concentrations ranging from 5 x 10(-7) to 10(-2) mol L(-1), with a detection limit of 3 x 10(-7) mol L(-1).
• The sensor demonstrated good reproducibility, a fast response time (10 s), and stability for over 3 months, with successful application in analyzing pharmaceutical formulations, baby food, and human plasma.

Conclusions:

• Bilirubin serves as an effective neutral carrier for constructing selective Ca(II) PVC membrane sensors.
• The choice of plasticizer significantly impacts sensor performance, with o-nitrophenyloctyl ether yielding optimal results.
• The developed sensor offers a reliable, sensitive, and rapid method for Ca(II) determination in diverse matrices and can be used in potentiometric titrations.