New and sensitive magnetic carbon paste electrode for voltammetry determination of morphine and methadone

Abstract

A novel and sensitive modified magnetic carbon paste electrode (MMCPE) is introduced. Magnetic carbon paste electrode (MCPE) was fabricated by a ring magnet that was put behind an insulin syringe packed with a mixture of graphite powder, multi-walled carbon nanotube (MWCNT), and paraffin oil. The surface of the MCPE was modified by immersing the electrode in a suspension of nanomagnetic core-shell (Fe3O4@SiO2) for 20 s, while nanomagnetic core-shells were physically adsorbed on the surface of the electrode by the magnetic force. The electrochemical behavior of morphine and methadone was studied at this new modified electrode. The efficiency of MMCPE was compared with a simple CPE and two modified CPEs prepared by mixtures of (graphite + MWCNT) and (graphite + MWCNT + nanomagnetic core-shell). The results showed that the sensitivity of MMCPE was higher than the three other CPEs. As a result, direct attachment of Fe3O4@SiO2 magnetic nanoparticles to the surface of the CPE by the magnetic force showed much higher surface area and electrode sensitivity compared to when the NPs were mixed with other compounds. Our studies showed this electrode is not selectable and can be used as a general electrode for all electro-active compounds. The electro-active surface area of MMCPE was obtained by Randles–Sevcik equation. Square wave voltammetry (SWV) was applied for determination of morphine and methadone in a linear range of 5.0 × 10–9 to 1.8 × 10–6 M and 1.0 × 10–8 to 8.0 × 10–6 M, with detection limits of 1.6 nM and 3 nM, respectively. Eventually, the proposed electrode was applied to determine morphine and methadone in urine samples.