Sensitive Potentiometric Determination of Amphetamine with an All-Solid-State Micro Ion-Selective Electrode

ABSTRACT

The development of amphetamine-ion-selective microelectrodes using electrochemical polymerization and microfabrication technologies is reported in this study. The microelectrodes include polypyrrole films electrochemically polymerized and doped with cosane anion ([3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻) as the internal solid contact layer between the polymeric sensitive membrane and platinum working microelectrode. Several poly(vinyl chloride)-type membranes with different compositions of plasticizers/ionophore were drop casted on the conducting polymer layer, polypyrrole[3,3′-Co(1,2-C₂B₉H₁₁)₂]. Potentiometric measurements were performed to calibrate the response of the developed chemical sensors. The sensor was highly sensitive to amphetamine using a membrane composition of 26 wt% poly (vinyl chloride), 63 wt% di-butyl phthalate, 6 wt% sodium tetraphenylborate, and 5 wt% dibenzo-18-crown 6-ether. A high and linear response was demonstrated within the concentration range from 10⁻⁵ to 10⁻³ M with a slope of 53 mV/decade and a limit of detection of 4 × 10⁻⁵ M. A Reilley diagram shows that the sensor signal is stable for a working pH between 1.50 and 8.50. The chemical sensor was highly selective to amphetamine when compared to other interfering ions and compounds including K⁺, Na⁺, , D,L-phenylalanine, caffeine, (±)-epinephrine bitartrate salt, and N-formylamphetamine using the fixed interference method with coefficients of selectivity (Log ) from −1.40 to −1.15.

KEYWORDS:

• Amphetamine
• cyclic voltammetry (CV)
• electrochemical impedance spectroscopy (EIS)
• micro ion-selective electrode (µISE)

Additional information

Funding

The authors acknowledge the financial support from the European Union’s Horizon 2020 research and innovation program entitled MicroMole and HEARTEN grant agreement Nos 653626 and 643694, respectively.