Stannum film electrode for square wave voltammetric determination of trace copper(II)

An anodic stripping voltammetric procedure for the determination of Cu(II) at an in situ-plated stannum film electrode (SnFE) was described. The results indicated that the SnFE had an attractive electroanalytical performance, with two distinct voltammetric stripping signals for copper and stannum, and showed the superior advantage for the determination of copper compared with the bismuth film electrode. Several experimental parameters were optimized. The SnFE exhibited highly linear behavior in the concentration range from 1.0 to 100.0 μg L⁻¹ of Cu(II) (r = 0.994) with the detection limit of 0.61 μg L⁻¹ (S/N = 3), and the relative standard deviation for a solution containing 40.0 μg L⁻¹ Cu(II) was 2.2% (n = 8). The procedure has been successfully applied for the determination of Cu(II) in lake water sample.     

Electrochemical oxidation of salicylic acid at well-aligned multiwalled carbon nanotube electrode and its detection

In this paper, an electrochemical sensor for sensitive and convenient determination of salicylic acid (SA) was constructed using well-aligned multiwalled carbon nanotubes as electrode material. Compared to the glassy carbon electrode, the electro-oxidation of SA significantly enhanced at the multiwalled carbon nanotube (MWCNT) electrode. The MWCNT electrode shows a sensitivity of 59.25 μA mM⁻¹, a low detection limit of 0.8 × 10⁻⁶ M and a good response linear range with SA concentration from 2.0 × 10⁻⁶ to 3.0 × 10⁻³ M. In addition, acetylsalicylic acid was determined indirectly after hydrolysis to SA and acetic acid, which simplified the detection process. The mechanism of electrochemical oxidation of SA at the MWCNT electrode is also discussed.     

Sensitive voltammetric determination of 2-mercaptobenzimidazole at electropolymerized nickel and copper tetraaminophthalocyanine membrane modified electrode

The voltammetric determination of 2-mercaptobenzimidazole (MBI) was studied by using a glassy carbon electrode (GCE) coated with polymeric nickel and copper tetraaminophthalocyanine (poly-NiTAPc and poly-CuTAPc) membrane. The polymeric membrane decreases the overpotential of oxidation of MBI by 136.2 and 115.0 mV and increases the oxidation peak current by about 3.4 and 3.3 times, while the reduction peak potential shifts positively by 113.0 and 84.1 mV and the peak current increases by about 10 and 7 times in 0.1 mol·l⁻¹ phosphate buffer solution (PBS) at pH = 2.0 for poly-NiTAPc and poly-CuTAPc, respectively, compared to the unmodified GCE. The results indicated that the developed electrode exhibited efficient electrocatalytic activity for MBI with relatively high sensitivity, stability, and long life. The oxidation and reduction peak currents of MBI were linear to its concentrations ranging from 8.0 × 10⁻⁵ to 1.0 × 10⁻³ mol·l⁻¹ at poly-NiTAPc and from 2.0 × 10⁻⁵ to 1.0 × 10⁻³ mol·l⁻¹ at poly-NiTAPc membranes modified electrodes, respectively, with a low limit of detection.     

Voltammetric determination of thiocytosine based on its electrocatalytic oxidation on the surface of carbon-paste electrode modified with cobalt Schiff base complexes

The electrochemical oxidation of thiocytosine on the surface of carbon-paste electrode modified with Schiff base (salophen derivatives) complexes of cobalt is studied. The effect of the substituents in the structure of salophen on the catalytic property of the modified electrode is investigated by using cyclic and differential pulse voltammetry. Cobalt (II)-5-nitrosalophen, because of its electrophilic functional groups, leads to a considerable enhancement in the catalytic activity, sensitivity (peak current), and a marked increase in the anodic potential of the modified electrode. The differential pulse voltammetry is applied as a very sensitive method for the detection of thiocytosine. The linear dynamic range was between 1 × 10⁻³ to 4 × 10⁻⁶ M with a slope of 0.0168 μA/μM, and the detection limit was 1 × 10⁻⁶ M. The modified electrode is successfully applied for the voltammetric detection of thiocytosine in human synthetic serum sample and also pharmaceutical preparations. A linear range from 1 × 10⁻³ to 1 × 10⁻⁵ M with a slope of 0.0175 μA/μM is resulted for the standard addition of thiocytosine spiked to the buffered human serum, which is differing from the curve in buffer solution about 4%. The electrode has a very good reproducibility (relative standard deviation for the slope of the calibration curve is less than 3.5% based on six determinations in a month), high stability in its voltammetric response and low detection limit for thiocytosine, and high electrochemical sensitivity with respect to other biological thiols such as cysteine.     

Sensitive voltammetric sensor of dihydromyricetin based on Nafion/SWNT-modified glassy carbon electrode

A novel voltammetric sensor, based on single-walled carbon nanotubes (SWNT) dispersed in Nafion and modified glassy carbon electrode (GCE), was fabricated and used to determine the trace amounts of dihydromyricetin (DMY). The electrochemical behavior of DMY at this sensor was investigated in 0.1 mol L⁻¹ sulfuric acid solutions + 0.1 mol L⁻¹ NaCl by cyclic voltammetry and squarewave voltammetry. Compared with bare GCE, the electrode presented an excellent response of DMY through an adsorption-controlled quasi-reversible process. Under the optimum conditions, the response peak currents were linear relationship with the DMY concentrations in the range of 1.0 × 10⁻⁷–1.0 × 10⁻⁵ mol L⁻¹ with a detection limit of 9 × 10⁻⁸ mol L⁻¹. Based on this voltammetric sensor, a simple and sensitive electroanalytical method for DMY was proposed and applied to quantitative determination of DMY in Ampelopsis grossedentata samples. In addition, the oxidation mechanism was proposed and discussed, which could be a reference for the pharmacological action of DMY in clinical study.     

Electrochemical evaluation and determination of antiretroviral drug fosamprenavir using boron-doped diamond and glassy carbon electrodes

Fosamprenavir is a pro-drug of the antiretroviral protease inhibitor amprenavir and is oxidizable at solid electrodes. The anodic oxidation behavior of fosamprenavir was investigated using cyclic and linear sweep voltammetry at boron-doped diamond and glassy carbon electrodes. In cyclic voltammetry, depending on pH values, fosamprenavir showed one sharp irreversible oxidation peak or wave depending on the working electrode. The mechanism of the oxidation process was discussed. The voltammetric study of some model compounds allowed elucidation of the possible oxidation mechanism of fosamprenavir. The aim of this study was to determine fosamprenavir levels in pharmaceutical formulations and biological samples by means of electrochemical methods. Using the sharp oxidation response, two voltammetric methods were described for the determination of fosamprenavir by differential pulse and square-wave voltammetry at the boron-doped diamond and glassy carbon electrodes. These two voltammetric techniques are 0.1 M H₂SO₄ and phosphate buffer at pH 2.0 which allow quantitation over a 4 × 10⁻⁶ to 8 × 10⁻⁵ M range using boron-doped diamond and a 1 × 10⁻⁵ to 1 × 10⁻⁴ M range using glassy carbon electrodes, respectively, in supporting electrolyte. All necessary validation parameters were investigated and calculated. These methods were successfully applied for the analysis of fosamprenavir pharmaceutical dosage forms, human serum and urine samples. The standard addition method was used in biological media using boron-doped diamond electrode. No electroactive interferences from the tablet excipients or endogenous substances from biological material were found. The results were statistically compared with those obtained through an established HPLC-UV technique; no significant differences were found between the voltammetric and HPLC methods.     

Electrochemical oxidation and determination of ceftriaxone on a glassy carbon and carbon-nanotube-modified glassy carbon electrodes

The electrochemical behavior of ceftriaxone was investigated on a carbon-nanotube-modified glassy carbon (GC-CNT) electrode in a phosphate buffer solution, pH = 7.40, and the results were compared with those obtained using the unmodified one [glassy carbon (GC) electrode]. During oxidation of ceftriaxone, an irreversible anodic peak appeared, using both modified and unmodified electrodes. Cyclic voltammetric studies indicated that the oxidation process is irreversible and diffusion-controlled. The number of electrons exchanged in the electrooxidation process was obtained, and the data indicated that ceftriaxone is oxidized via a one-electron step. The results revealed that carbon nanotube promotes the rate of oxidation by increasing the peak current. In addition, ceftriaxone was oxidized at lower potentials, which thermodynamically is more favorable. These results were confirmed by impedance measurements. The electron-transfer coefficients and heterogeneous electron-transfer rate constants for ceftriaxone were reported using both the GC and GC-CNT electrodes. Furthermore, the diffusion coefficient of ceftriaxone was found to be 2.74 × 10⁻⁶ cm² s⁻¹. Binding of ceftriaxone to human serum albumin forms a kind of electroreactive species. The percentage of interaction of ceftriaxone with protein was also addressed. A sensitive, simple, and time-saving differential-pulse voltammetric procedure was developed for the analysis of ceftriaxone, using the GC-CNT electrode. Ceftriaxone can be determined with a detection limit of 4.03 × 10⁻⁶ M with the proposed method.     

Novel reductive–reductive mode electrochemical detection of Rohypnol following liquid chromatography and its determination in coffee

Rohypnol (flunitrazepam) has been successfully determined in coffee by high performance liquid chromatography dual electrode detection (LC-DED) in the dual reductive mode. Initial studies were performed to optimise the chromatographic conditions and these were found to be 50% acetonitrile, 50% 50 mM pH 2.0 phosphate buffer at a flow rate of 0.75 mL min⁻¹, employing a Hypersil C₁₈, 5 μm, 250 mm × 4.6 mm column. Cyclic voltammetric studies were made to ascertain the redox behaviour of Rohypnol at a glassy carbon electrode over the pH range 2–12. Hydrodynamic voltammetry was used to optimise the applied potential at the generator and detector cells; these were identified to be −2.4 V and +0.8 V for the redox mode and −2.4 V and −0.1 V for the dual reductive mode respectively. A linear range of 0.5–100 μg mL⁻¹, with a detection limit of 20 ng mL⁻¹ was obtained for the dual reductive mode. Further studies were then performed to identify the optimum conditions required for the LC-DED determination of Rohypnol in beverage samples. A convenient and rapid method for the determination of Rohypnol in beverage samples was developed using a simple sample pre-treatment procedure. A recovery of 95.5% was achieved for a sample of white coffee fortified at 9.6 μg mL⁻¹ Rohypnol.     

Langmuir–Blodgett film of tetraoxocalix[2]arene[2]triazine modified electrode for voltammetric determination of copper ion

In the present work, a new voltammetric sensor, Langmuir–Blodgett (LB) film of tetraoxocalix[2]arene[2]triazine (TOCT) modified glassy carbon electrode (LB_TOCT-GCE), for trace analysis of copper ion in water samples, was prepared. The morphology of LB_TOCT-GCE was characterized by cyclic voltammetric method, electrochemical impedance spectroscopy, and atomic force microscope. The recognizing mechanism of LB_TOCT-GCE for copper ion in aqueous solution was discussed. Under the optimum experimental conditions, using square wave stripping voltammetry and accumulation time of 300 s, the peak currents were linear relationship with Cu²⁺ concentrations in the range of 2 × 10⁻⁹ to 1 × 10⁻⁶ mol L⁻¹, with detection limit of 1 × 10⁻¹⁰ mol L⁻¹. By this method, real samples (lake water, drinking water, and city wastewater) were analyzed with satisfactory results. In addition, the fabricated electrode exhibited a distinct advantage of simple preparation, non-toxicity, good reproducibility, and stability.     

Fabrication of gold nanoparticles/polypyrrole composite-modified electrode for sensitive hydroxylamine sensor design

A highly sensitive hydroxylamine (HA) electrochemical sensor is developed based on electrodeposition of gold nanoparticles with diameter of 8 nm on the pre-synthesized polypyrrole matrix and formed gold nanoparticles/polypyrrole (GNPs/PPy) composite on glassy carbon electrode. The electrochemical behavior and electrocatalytic activity of the composite-modified electrode are investigated. The GNPs/PPy composite exhibits a distinctly higher electrocatalytic activity for the oxidation of HA than GNPs with twofold enhancement of peak current. The enhanced electrocatalytic activity is attributed to the synergic effect of the highly dispersed gold metal particles and PPy matrix. The overall numbers of electrons involved in HA oxidation, the electron transfer coefficient, catalytic rate constant, and diffusion coefficient are investigated by chronoamperometry. The sensor presents two wide linear ranges of 4.5 × 10⁻⁷–1.2 × 10⁻³ M and 1.2 × 10⁻³–19 × 10⁻³ M with the detection limit of 4.5 × 10⁻⁸ M (s/n = 3). In addition, the proposed electrode shows excellent sensitivity, selectivity, reproducibility, and stability properties.     

FAD-modified SiO2/ZrO2/C ceramic electrode for electrocatalytic reduction of bromate and iodate

SiO₂/ZrO₂/C carbon ceramic material with composition (in wt%) SiO₂ = 50, ZrO₂ = 20, and C = 30 was prepared by the sol–gel-processing method. A high-resolution transmission electron microscopy image showed that ZrO₂ and the graphite particles are well dispersed inside the matrix. The electrical conductivity obtained for the pressed disks of the material was 18 S cm⁻¹, indicating that C particles are also well interconnected inside the solid. An electrode modified with flavin adenine dinucleotide (FAD) prepared by immersing the solid SiO₂/ZrO₂/C, molded as a pressed disk, inside a FAD solution (1.0 × 10⁻³ mol L⁻¹) was used to investigate the electrocatalytic reduction of bromate and iodate. The reduction of both ions occurred at a peak potential of −0.41 V vs. the saturated calomel reference electrode. The linear response range (lrr) and detection limit (dl) were: BrO₃ ⁻, lrr = 4.98 × 10⁻⁵–1.23 × 10⁻³ mol L⁻¹ and dl = 2.33 μmol L⁻¹; IO₃ ⁻, lrr = 4.98 × 10⁻⁵ up to 2.42 × 10⁻³ and dl = 1.46 μmol L⁻¹ for iodate.     

Simultaneous and sensitive determination of procaine and its metabolite for pharmaceutical quality control and pharmacokinetic research by using a graphite paste electrode

A simple, rapid, sensitive, and accurate method for simultaneous electrochemical determination of procaine and its metabolite (p-aminobenzoic acid, PABA) for pharmaceutical quality control and pharmacokinetic research was developed using a graphite paste electrode. The differential pulse voltammetric results revealed that procaine and p-aminobenzoic acid, respectively, showed well-defined anodic oxidation peaks on a carbon paste electrode with a current peak separation of 155 mV at a scan rate of 100 mV s⁻¹. This well separation of the current peaks for these two compounds in voltammetry enables us to simultaneously determine them. Good linearity (r > 0.998) between oxidation peak current and concentration was obtained in the range of 5.0 × 10⁻⁷–5.0 × 10⁻⁵ M for procaine and 5.0 × 10⁻⁷–2.0 × 10⁻⁵ M for PABA in pH 4.50 acetate buffer solution. The detection limit for both analytes is 5 × 10⁻⁸ M (S/N = 3:1). The present voltammetric method has been successfully used to determine trace p-aminobenzoic acid in procaine hydrochloride injection and procaine in plasma with a linear relationship of current to its concentration ranging from 1.0 × 10⁻⁶ to 5.0 × 10⁻⁵ M (correlation coefficient of 0.9981) with a low detection limit of 5.0 × 10⁻⁷ M (S/N = 3:1). This validated method is promising to the study of pharmacokinetics in Sprague–Dawley rat and rabbit plasma after an intravenous administration of procaine hydrochloride injection.     

Immobilization of flavine adenine dinucleotide onto nickel oxide nanostructures modified glassy carbon electrode: fabrication of highly sensitive persulfate sensor

A simple method was used to fabricate flavin adenine dinucleotide (FAD)/NiOx nanocomposite on the surface of glassy carbon (GC) electrode. Cyclic voltammetry technique was applied for deposition nickel oxide nanostructures onto GC surface. Owing to its high biocompatibility and large surface area of nickel oxide nanomaterials with immersing the GC/NiOx-modified electrode into FAD solution for a short period of time, 10–140 s, a stable thin layer of the FAD molecules immobilized onto electrode surface. The FAD/NiOx films exhibited a pair of well-defined, stable, and nearly reversible CV peaks at wide pH range (2–10). The formal potential of adsorbed FAD onto nickel oxide nanoparticles film, E ^o′ vs. Ag/AgCl reference electrode is −0.44 V in pH 7 buffer solutions was similar to dissolved FAD and changed linearly with a slope of 58.6 mV/pH in the pH range 2–10. The surface coverage and heterogeneous electron transfer rate constant (k _s ) of FAD immobilized on NiOx film glassy carbon electrode are 4.66 × 10⁻¹¹ mol cm⁻² and 63 ± 0.1 s⁻¹, indicating the high loading ability of the nickel oxide nanoparticles and great facilitation of the electron transfer between FAD and nickel oxide nanoparticles. FAD/NiOx nanocomposite-modified GC electrode shows excellent electrocatalytic activity toward S₂O₈²⁻ reduction at reduced overpotential. Furthermore, rotated modified electrode illustrates good analytical performance for amperometric detection of S₂O₈²⁻. Under optimized condition, the concentration calibration range, detection limit, and sensitivity were 3 μM–1.5 mM, 0.38 μM and 16.6 nA/μM, respectively.     

Voltammetric detection of paraquat pesticide on a phthalocyanine-based pyrolitic graphite electrode

This work describes the application of an ordinary pyrolitic graphite electrode modified by metallophthalocyanine allied to square wave voltammetry for the study of the electrochemical behavior of the herbicide paraquat and the development of a method for its analytical determination in natural water samples. Preliminary experiments indicated that the best responses, considering the intensities of the current and voltammetric profile for the paraquat reduction process, were obtained when the electrode modified by cobalt phthalocyanine was employed, which had a better catalytic activity as a result of this modification compared with that for an unmodified electrode and electrodes modified by iron, manganese and the acid form of the phthalocyanines. Studies of the concentration of cobalt phthalocyanine and the adsorption time showed that 1.0 × 10⁻⁴ mol L⁻¹ cobalt phthalocyanine with an adsorption time of 10 min was sufficient to obtain reliability and stability of modification for employment in the development of the electroanalytical procedure for paraquat determination in natural water samples. The variation in pH of a 0.10 mol L⁻¹ Britton–Robinson buffer solution and the square wave parameters indicated that the best conditions to reduce paraquat were pH 7.0, a frequency of 100 s⁻¹, a scan increment of 2 mV and a square wave amplitude of 50 mV. Under such conditions, the variation of paraquat concentrations from 5.00 × 10⁻⁷ to 2.91 × 10⁻⁵ mol L⁻¹ showed a linear relation, with detection and quantification limits of 26.53 and 88.23 μg L⁻¹; those values were lower than the maximum limits for drinking water permitted by the Brazilian Environmental Council (100 μg L⁻¹), indicating that the method could be employed to analyze paraquat in drinking water samples.     

Fast and sensitive determination of captopril by voltammetric method using ferrocenedicarboxylic acid modified carbon paste electrode

A ferrocenedicarboxylic acid modified carbon paste electrode was constructed and used as a fast and sensitive tool for the determination of captopril at trace level. It has been shown by direct current cyclic voltammetry and double step chronoamperometry that ferrocenedicarboxylic acid can catalyze the oxidation of captopril in aqueous buffer solution and produces a sharp oxidation peak current at about +0.49 vs. Ag/AgCl reference electrode. The square wave voltammetric peak currents of the electrode increased linearly with the corresponding captopril concentration in the range of 3.0 × 10⁻⁷–1.4 × 10⁻⁴M with a detection limit of 9.1 × 10⁻⁸ M. The influence of pH and potential interfering substances on the determination of captopril were studied. Electrochemical impedance spectroscopy was used to study the charge transfer properties at the electrode–solution interface. Finally, the sensor was examined as a selective, simple, and precise new electrochemical sensor for the determination of captopril in real samples, such as drug and urine, with satisfactory results.     

Solid state electrochemical of the erbium hexacyanoferrate-modified carbon ceramic electrode and its electrocatalytic oxidation of <Emphasis Type="SmallCaps">l</Emphasis>-cysteine

A kind of erbium hexacyanoferrate (ErHCF)-modified carbon ceramic electrodes (CCEs) fabricated by mechanically attaching ErHCF samples to the surface of CCEs derived from sol–gel technique was proposed. The resulting modified electrodes exhibit well-defined redox responses with the formal potential of +0.215 V [vs saturated calomel electrode (SCE)] at a scan rate of 20 mV s⁻¹ in 0.5 M KCl (pH 7) solution. The voltammetric characteristics of the ErHCF-modified CCEs were investigated by voltammetry. Attractively, the ErHCF-modified CCEs presented good electrocatalytic activity with a marked decrease in the overvoltage about 400 mV for l-cysteine oxidation. The calibration plot for l-cysteine determination was linear at 5.0 × 10⁻⁶–1.3 × 10⁻⁴ M with a linear regression equation of I(A) = 0.558 + 0.148c (μM) (R ² = 0.9989, n = 20), and the detection limit was 2 × 10⁻⁶ M (S/N = 3). At last, the ErHCF-modified CCEs were used for amperometric detection of l-cysteine in real samples.     

Silica-modified electrode for the selective detection of mercury

Pure silica particles were dispersed within carbon paste and the resulting modified electrode was applied to the selective voltammetric detection of mercury(II) species after their accumulation at open circuit. The remarkable selectivity observed between pH 4 and 7 was attributed to the intrinsic adsorption mechanism which involves a condensation reaction between mercury(II) hydroxide and hydroxyl groups on the silica surface, leading to the formation of an inner-sphere-type surface complex. After optimization with respect to the electrode composition, the detection medium, and the voltammetric scan mode, a linear response was obtained in the concentration range between 2 × 10⁻⁷ M to 1 × 10⁻⁵ M, by applying anodic stripping square wave voltammetry. Various silica samples were used and their sorption behavior was discussed in relation to their specific surface area and porosity. The effect of chloride and pH on the accumulation of mercury(II) on silica was also investigated. Received: 4 September 1999 / Accepted: 5 January 2000     

Covalent modification of a glassy carbon electrode with penicillamine for simultaneous determination of hydroquinone and catechol

A simple and highly selective electrochemical method has been developed for the simultaneous determination of hydroquinone (HQ) and catechol (CC) at a glassy carbon electrode covalently modified with penicillamine (Pen). The electrode is used for the simultaneous electrochemical determination of HQ and CC and shows an excellent electrocatalytical effect on the oxidation of HQ and CC upon cyclic voltammetry in acetate buffer solution of pH 5.0. In differential pulse voltammetric measurements, the modified electrode was able to separate the oxidation peak potentials of HQ and CC present in binary mixtures by about 103 mV although the bare electrode gave a single broad response. The determination limit of HQ in the presence of 0.1 mmol L⁻¹ CC was 1.0 × 10⁻⁶ mol L⁻¹, and the determination limit of CC in the presence of 0.1 mmol L⁻¹ HQ was 6.0 × 10⁻⁷ mol L⁻¹. The method was applied to the simultaneous determination of HQ and CC in a water sample. It is simple and highly selective.     

Method validation in quantitative electrochemical analysis of colchicine using glassy carbon electrode

A cathodic differential pulse voltammetric determination of colchicine was validated using a glassy carbon electrode in HClO₄/H₃PO₄ 0.01 M. Colchicine gives an irreversible, diffusion-controlled peak at −862 mV vs. Ag/AgCl reference electrode. The cathodic peak is strongly influenced by a more alkaline environment with a shift towards more negative potentials. Method optimization was carried out in parallel for three types of electrodes (glassy carbon, mercury film and bismuth film coated glassy carbon). The cathodic peak current is higher using film-coated electrodes, but shows poorer intra-day reproducibility and a longer analysis time due to film renewal. Thus, a bare glassy carbon electrode was used to determine colchicine in the concentration range of 2.4 − 50 μg mL⁻¹ (R ² = 0.9998, n = 5), with a calculated detection limit of 0.80 μg mL⁻¹. The proposed method was characterized according to ICH Harmonized Tripartite Guidance Q2(R1) by validation parameters (selectivity, linearity, accuracy, fidelity, limit of detection, limit of quantification) and it was successfully applied for the determination of colchicine from tablets, without the interference of the excipients. The method’s performances were evaluated and compared with both a known polarographic method and the official quantitative spectrophotometric determination from the Romanian Pharmacopoeia, Xth edition, respectively.      

Electrocatalytic oxidation of quinine sulfate at a multiwall carbon nanotubes-ionic liquid modified glassy carbon electrode and its electrochemical determination

The electrocatalytic oxidation of quinine sulfate (QS) was investigated at a glassy carbon electrode, modified by a gel containing multiwall carbon nanotubes (MWCNTs) and room-temperature ionic liquid of 1-Butyl-3-methylimidazolium hexafluorophate (BMIMPF₆) in 0.10 M of phosphate buffer solution (PBS, pH 6.8). It was found that an irreversible anodic oxidation peak of QS with E _pa as 0.99 V appeared at MWCNTs-RTIL/glassy carbon electrode (GCE). The electrode reaction process was a diffusion-controlled one and the electrochemical oxidation involved two electrons transferring and two protons participation. Furthermore, the charge-transfer coefficient (α), diffusion coefficient (D), and electrode reaction rate constant (k _f) of QS were found to be 0.87, 7.89 × 10⁻³ cm²⋅s⁻¹ and 3.43 × 10⁻² s⁻¹, respectively. Under optimized conditions, linear calibration curves were obtained over the QS concentration range 3.0 × 10⁻⁶ to 1.0 × 10⁻⁴ M by square wave voltammetry, and the detection limit was found to be 0.44 μM based on the signal-to-noise ratio of 3. In addition, the novel MWCNTs-RTIL/GCE was characterized by the electrochemical impedance spectroscopy and the proposed method has been successfully applied in the electrochemical quantitative determination of quinine content in commercial injection samples and the determination results could meet the requirement.