Simultaneous Detection of Morphine and Codeine in the Presence of Ascorbic Acid and Uric Acid and in Human Plasma at Nafion Single-Walled Carbon Nanotube Thin-Film Electrode

Abstract

In clinical settings, the dosing and differential diagnosis of the poisoning of morphine (MO) and codeine (CO) is challenging due to interindividual variations in metabolism. However, direct electrochemical detection of these analytes from biological matrices is inherently challenging due to interference from large concentrations of anions, such as ascorbic acid (AA) and uric acid (UA), as well as fouling of the electrode by proteins. In this work, a disposable Nafion-coated single-walled carbon nanotube network (SWCNT) electrode was developed. We show facile electron transfer and efficient charge separation between the interfering anions and positively charged MO and CO, as well as significantly reduced matrix effect in human plasma. The Nafion coating alters the voltammetric response of MO and CO, enabling simultaneous detection. With this SWCNT/Nafion electrode, two linear ranges of 0.05–1 and 1–10 μM were found for MO and one linear range of 0.1–50 μM for CO. Moreover, the selective and simultaneous detection of MO and CO was achieved in large excess of AA and UA, as well as, for the first time, in unprocessed human plasma. The favorable properties of this electrode enabled measurements in plasma with only mild dilution and without the precipitation of proteins.

Disposable Nafion-Coated Single-Walled Carbon Nanotube Test Strip for Electrochemical Quantitative Determination of Acetaminophen in a Finger-Prick Whole Blood Sample

“…This result is in line with a similar passivation study carried out with a Nafion-coated SWCNT electrode in previous research. 29 Furthermore, the electrodes used to measure 50 μM acetaminophen in whole blood (see Table 1 ) were also used to measure 50 μM acetaminophen in PBS. After wiping away the whole blood, washing with a 40 μL drop of PBS, and confirming that the background returns to that of blank PBS, a mean peak current of 1.83 ± 0.09 μM was obtained.…”

“…When selectivity is achieved by an anodic shift of the oxidation peak, however, interference from other endogenous chemicals is expected. 29 , 30 Recent reports have shown selective detection of acetaminophen in urine samples and blood serum. These reports, however, also relied on sample processing including liquid–liquid extraction, precipitation of proteins, and centrifugation as well as considerable dilution of the sample matrix.…”

Effect of Electrochemical Oxidation on Physicochemical Properties of Fe‐Containing Single‐Walled Carbon Nanotubes

“…For MO, values of the first oxidation peak around + 0.4 V are only shown, as it is most frequently used for determining morphine. [9,36,37] Interestingly, no remarkable changes in the sensitivity towards any of the biomolecules were obtained, even though clear physical and chemical changes were observed with XAS and TEM/STEM. Thus, at least in case of detection of PA, MO and OXC, there seems to be no significant difference in the active electrochemical area, whether majority of the Fe nanoparticles are in metallic or in oxidized state in the SWCNT network.…”

“…In fact, we have shown that as-fabricated pristine CNTs are a suitable material for the detection of neurotransmitter dopamine [5,6] and analgesics such as oxycodone, [7] fentanyl, [8] morphine and codeine. [9] The main methods for fabricating CNTs are chemical vapor deposition, electric discharge and laser ablation, where transition metal particles (Co, Fe, Ni) are used for catalyzing the growth of CNTs. [10] Due to the fabrication conditions, assynthesized CNTs typically consist of residual metal particles, as well as a carbonaceous impurities, for example amorphous carbon and graphitic particles.…”

“…[15,16] Furthermore, we have extensively studied the suitability of pristine iron containing single-walled carbon nanotubes (SWCNTs) for the detection of various analgesics. [7][8][9] Despite these studies, at this stage, there are no clear indications regarding the required amount of iron that enhances electrocatalysis towards opioids, and whether the electrocatalytic properties of Fe-SWCNTs be improved with simple oxidative pretreatment.…”