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.

介绍了一种新颖而灵敏的改性磁性碳糊电极（MMCPE）。磁性碳糊电极（MCPE）由环形磁体制成，该环形磁体置于装有石墨粉，多壁碳纳米管（MWCNT）和石蜡油的混合物的胰岛素注射器后面。通过将电极浸入纳米磁性核-壳（Fe ₃ O ₄ @SiO ₂）20 s，纳米磁性核壳被磁力物理吸附在电极表面上。在这种新型修饰电极上研究了吗啡和美沙酮的电化学行为。将MMCPE的效率与一个简单的CPE和由（石墨+ MWCNT）和（石墨+ MWCNT +纳米磁性核-壳）的混合物制备的两种改性CPE进行了比较。结果表明，MMCPE的灵敏度高于其他三种CPE。结果，Fe ₃ O ₄ @SiO ₂直接附着与将NP与其他化合物混合时相比，通过磁力到达CPE表面的磁性纳米粒子显示出更高的表面积和电极敏感性。我们的研究表明，该电极不是可选的，可以用作所有电活性化合物的通用电极。通过Randles–Sevcik方程获得MMCPE的电活性表面积。方波伏安法（SWV）用于在5.0×10 ^–9至1.8×10 ^–6  M和1.0×10 ^–8至8.0×10 ^–6  M的线性范围内测定吗啡和美沙酮，检测限为1.6分别为nM和3 nM。最终，建议的电极用于测定尿液样品中的吗啡和美沙酮。