Determination of pholcodine alone or in combination with ephedrine in human plasma using fluorescence spectroscopy

In this study, sensitive, facile, and cost-effective spectrofluorimetric approaches were developed for the determination of pholcodine and ephedrine. Method I is a novel spectrofluorimetric method depending on measuring the native fluorescence of pholcodine at 337 nm after excitation at 284 nm over a concentration range of 0.01-2.4 μg/mL. The method sensitivity reached quantitation and detection limits down to 10.0 and 5.0 ng/mL, respectively. Method II relied on the simultaneous estimation of pholcodine and ephedrine using synchronous fluorimetry for the first time. The cited drugs were measured concurrently at 286 and 304 nm for pholcodine and ephedrine, respectively at Δλ of 40 nm without interference. Excellent linear relationship between concentration and response was obtained over the ranges of 0.05-6.0 μg/mL and 0.02-1.0 μg/mL for pholcodine and ephedrine, respectively. The method showed distinct sensitivity and exhibited quantitation limits of 20.0 and 10.0 ng/mL and detection limits of 10.0 and 5.0 ng/mL, respectively. The method was successfully applied to the syrup dosage form. The two developed approaches were also applied to in-vitro plasma samples, showing good bioanalytical applicability and providing further insights for monitoring drug abuse. The proposed methods were validated according to ICHQ2(R1) guidelines. The proposed methodologies' greenness profiles were evaluated using two greenness assessment tools.

Magnetic-molecularly imprinted polymers in electrochemical sensors and biosensors

Magnetic particles, as well as molecularly imprinted polymers, have revolutionized separation and bioanalytical methodologies in the 1980s due to their wide range of applications. Today, biologically modified magnetic particles are used in many scientific and technological applications and are integrated in more than 50,000 diagnostic instruments for the detection of a huge range of analytes. However, the main drawback of this material is their stability and high cost. In this work, we review recent advances in the synthesis and characterization of hybrid molecularly imprinted polymers with magnetic properties, as a cheaper and robust alternative for the well-known biologically modified magnetic particles. The main advantages of these materials are, besides the magnetic properties, the possibility to be stored at room temperature without any loss in the activity. Among all the applications, this work reviews the direct detection of electroactive analytes based on the preconcentration by using magnetic-MIP integrated on magneto-actuated electrodes, including food safety, environmental monitoring, and clinical and pharmaceutical analysis. The main features of these electrochemical sensors, including their analytical performance, are summarized. This simple and rapid method will open the way to incorporate this material in different magneto-actuated devices with no need for extensive sample pretreatment and sophisticated instruments.

Voltammetric Analysis of Ephedrine in Pharmaceutical Dosage Forms and Urine Using poly(Nile Blue A) Modified Glassy Carbon Electrode

OBJECTIVE

The electrochemical analysis of ephedrine which is a sympathometric drug has been studied using poly(Nile blue A) modified glassy carbon electrodes, cyclic voltammetry, differential pulse voltammetry and square wave voltammetry.

METHODS

The modified electrodes were prepared by potential cycling electropolymerization of Nile blue A in 0.1 M phosphate buffer solution at pH 6.0. The redox behavior of ephedrine was investigated in different buffer solutions at pH values between 5.5 and 9.0.

RESULTS

Scan rate studies showed that the electron transfer reaction of ephedrine was diffusion controlled. A linear response was obtained between the peak current and the ephedrine concentration in the range of 0.6 to 100 μM with a limit of detection of 2.91×10^-3 μM for differential pulse voltammetry in Britton-Robinson buffer solution at pH 9.0. The linearity range of ephedrine in human urine was between 1.0 and 100 μM with a detection limit of 8.16 nM.

CONCLUSION

The recovery studies in both pharmaceutical dosage forms and urine showed that the proposed method ensured good selectivity, precision and accuracy without any interference from inactive excipients.

Interpol review of controlled substances 2016-2019

This review paper covers the forensic-relevant literature in controlled substances from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.

Multi-phase extraction of ephedrine from Pinellia ternata and herbal medicine using molecular imprinted polymer coated ionic liquid-based silica

INTRODUCTION

Ephedrine is a typical compound found in lots of plant species that is used in several medicines for the treatment of asthma and bronchitis. However, excess amounts are harmful to humans, so it needs to be removed.

OBJECTIVE

This study developed a multi-phase extraction (MPE) method with a molecular imprinted polymer (MIP) coated ionic liquid (IL)-based silica (SiO₂ @IL@MIP) to simultaneously extract and separate ephedrine from Pinellia ternata, 10 medicines, and urine samples.

METHODS

IL was immobilized on silica. Subsequently, the IL was combined with the functional monomer, followed by the addition of the crosslinker and template. The resulting sorbent was applied to the MPE, and the extraction, washing and elution solvents were evaluated.

RESULTS

Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) confirmed the synthesis of SiO₂ @IL@MIP. A maximum adsorption amount of 5.76 mg/g was obtained at 30°C at a neutral pH. In MPE, 10.00 mL of methanol could extract all the ephedrine from Pinellia ternata. The interference was removed by washing with 4.00 mL of water, ethanol, and acetonitrile. Finally, 8.00 mL of methanol/acetic acid (99:1, v/v) was applied as the elution solvent. The following were extracted: 5.50 μg/g of ephedrine from Pinellia ternata, 0.00-46.50 μg/g from the 10 herbal medicines, and 68.70-102.80 μg/mL in the urine samples.

CONCLUSION

The proposed method was applied successfully to the simultaneously extraction and separation of ephedrine from plants and medicines. These results are expected to provide important data for the development of new methods for the separation and purification of bioactive compounds.

Magnetic molecularly imprinted electrochemical sensors: A review

The preparation and practical applications of molecularly imprinted electrochemical sensors (MIECSs) remain challenging due to issues involving electrode surface renewal modes, low adsorption capacities, and sample preparation speeds. To solve these issues, magnetic molecularly imprinted electrochemical sensors (MMIECSs) have been extensively explored by various groups. Recently, MMIECSs fabricated based on diverse strategies have yielded insight into the development of MIECSs, and they have provided effective paths for sample preparation, immobilization and renewal of molecularly imprinted polymers (MIPs) on the electrode surface, leading to promising performances of MIECSs. This review comprehensively describes the research advances for various types of MMIECSs and their applications in the fields of food safety, environmental monitoring, and clinical and pharmaceutical analysis. Based on our understanding of MMIECSs, the literature in this field is thoroughly explored and classified in this review. The challenges existing in this research area and some potential strategies for the rational design of high-performance MMIECS are also outlined.

Large interlayer spacing Nb4C3Tx (MXene) promotes the ultrasensitive electrochemical detection of Pb2+ on glassy carbon electrodes

Large interlayer spacing Nb₄C₃T_x (MXene) promotes the ultrasensitive electrochemical detection of Pb²⁺ on glassy carbon electrodes

Correction to: Magnetic-core@dual-functional-shell nanocomposites with peroxidase mimicking properties for use in colorimetric and electrochemical sensing of hydrogen peroxide

A self-sacrificing catalytic method is described for the preparation of magnetic core/dual-functional-shell nanocomposites composed of magnetite, gold and Prussian blue (type Fe₃O₄@Au-PB). Two reaction pathways are integrated. The first involves chemical dissolution of Fe₃O₄ (the self-sacrificing step) by acid to release ferrous ions which then reacts with hexacyanoferrate(IV) to generate PB in the proximity of the magntic nanoparticles (MNPs). The second involves the reduction of tetrachloroaurate by hydroxylamine to generate gold under the catalytic effect of the MNPs. At the end, the MNP@Au-PB nanocomposite is formed. This method exploits both the chemical reactivity and catalytic effect of the MNPs in a single step. The multi-function material was applied (a) in an optical assay for H₂O₂; (b) in an amperometric assay for H₂O₂; (c) in an enzymatic choline assay using immobilized choline oxidase. The limit of electrochemical detection of H₂O₂ (at a potential as low as 50 mV) is 1.1 μM which is comparable or better than most analogous methods. The sensors display superior performance compared to the use of conventional core@single-shell (MNP@Au-PB) nanomaterials. Graphical abstract A self-sacrificing catalytic method is described to prepare magnetic core/dual-functional-shell nanocomposites composed of magnetic nanoparticle, gold and Prussian blue (type MNP@Au-PB). The nanocomposites worded well as candidates to develop colorimetric and electrochemical sensors of H₂O₂ with superior performance to analogues.

Modifying the reactivity of copper (II) by its encapsulation into polydimethylsiloxane: A selective sensor for ephedrine-like compounds

This paper demonstrates that the reactivity of copper (II) can be modified through its entrappment in a polymeric matrix of polydimethylsiloxane (PDMS), which makes possible the reaction into the support instead of in solution. Amino-containing compounds such as amino acids, proteins and sugars, which react with Cu (II) in solution, do not react inside the polymer. As a prove of concept, a highly specific Cu (II) PDMS-based sensor for ephedrines has been developed in this work. When the sensors are put into contact with solutions of these drugs under basic conditions, a change in their color from pale green to purple is observed. This change enables the visual identification of ephedrine (Eph) in a few min, as well as its quantification using both reflectance diffuse measurements of the sensors and color intensities of their digitalized images. The sensors show suitable analytical performance for Eph-like compounds, and provide limits of detection (LODs) of 0.3-1.0 mg, and relative standard deviations (RDSs) < 10%. The method has been applied to both the qualitative and quantitative analysis of different types of liquid and solid samples (intravenous injection solution of Eph, dietary supplements and illicit drug-street samples) without the need of any special sample treatment.

Decorated single-enantiomer phosphoramide-based silica/magnetic nanocomposites for direct enantioseparation

The nano-composites Fe₃O₄@SiO₂@PTA(+) and Fe₃O₄@SiO₂@PTA(−) (PTA: phosphoric triamide) were prepared and used for the chiral separation of five racemic mixtures.

Magnetic-core@dual-functional-shell nanocomposites with peroxidase mimicking properties for use in colorimetric and electrochemical sensing of hydrogen peroxide

A self-sacrificing catalytic method is described for the preparation of magnetic core/dual-functional-shell nanocomposites composed of magnetite, gold and Prussian Blue (type Fe₃O₄@Au-PB). Two reaction pathways are integrated. The first involves chemical dissolution of Fe₃O₄ (the self-sacrificing step) by acid to release ferrous ions which then reacts with hexacyanoferrate(IV) to generate PB in the proximity of the magntic nanoparticles (MNPs). The second involves the reduction of tetrachloroaurate by hydroxylamine to generate gold under the catalytic effect of the MNPs. At the end, the MNPs@Au-PB nanocomposite is formed. This method exploits both the chemical reactivity and catalytic effect of the MNPs in a single step. The multi-function material was applied (a) in an optical assay for H₂O₂; (b) in an amperometric assay for H₂O₂; (c) in an enzymatic choline assay using immobilized choline oxidase. The limit of electrochemical detection of H₂O₂ (at a potential as low as 50 mV) is 1.1 μM which is comparable or better than most analogous methods. The sensors display superior performance compared to the use of conventional core@single-shell (MNPs@PB) nanomaterials. Graphical abstract A self-sacrificing catalytic method is described to prepare magnetic core/dual-functional-shell nanocomposites composed of magnetic nanoparticle, gold and Prussian Blue (type MNP@Au-PB). The nanocomposites work well as candidates to develop colorimetric and electrochemical sensors of H₂O₂ with superior performance to analogues.

Sensitive and simple simultaneous determination of morphine and codeine using a Zn2SnO4nanoparticle/graphene composite modified electrochemical sensor

Simultaneous determination of morphine and codeine using a nanocomposite modified electrochemical sensor.