Electrodeposition of gold nanoclusters on overoxidized polypyrrole film modified glassy carbon electrode and its application for the simultaneous determination of epinephrine and uric acid under coexistence of ascorbic acid

A novel biosensor was fabricated by electrochemical deposition of gold nanoclusters on ultrathin overoxidized polypyrrole (PPyox) film, formed a nano-Au/PPyox composite on glassy carbon electrode (nano-Au/PPyox/GCE). The properties of the nanocomposite have been characterized by field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD) and electrochemical investigations. The nano-Au/PPyox/GCE had strongly catalytic activity toward the oxidation of epinephrine (EP), uric acid (UA) and ascorbic acid (AA), and resolved the overlapping voltammetric response of EP, UA and AA into three well-defined peaks with a large anodic peak difference. The catalytic peak currents obtained from differential pulse voltammetry increased linearly with increasing EP and UA concentrations in the range of 3.0 × 10⁻⁷ to 2.1 × 10⁻⁵ M and 5.0 × 10⁻⁸ to 2.8 × 10⁻⁵ M with a detection limit of 3.0 × 10⁻⁸ and 1.2 × 10⁻⁸ M (s/n = 3), respectively. The results showed that the modified electrode can selectively determine EP and UA in the coexistence of a large amount of AA. In addition, the sensor exhibited excellent sensitivity, selectivity and stability. The nano-Au/PPyox/GCE has been applied to determination of EP in epinephrine hydrochloride injection and UA in urine samples with satisfactory results.     

A novel protocol for ultra-trace detection of pesticides: Combined electrochemical reduction of Ellman's reagent with acetylcholinesterase inhibition

This paper proposed a novel method for ultra-trace detection of pesticides combining electrochemical reduction of Ellman's reagent with acetylcholinesterase (AChE) inhibition. The amperometric biosensor, fabricated by immobilizing AChE on multi-walled carbon nanotubes-chitosan (MWCNTs-Chi) nanocomposites modified glassy carbon electrode, enjoyed high sensitivity owing to the excellent conductivity and favourable biocompatibility of MWCNTs-Chi nanocomposites. Meanwhile, the sensitivity of the biosensor was further enhanced using the electrochemical reduction signal of DTNB for determination. Under optimum conditions, methyl parathion was detected based on its inhibition effect on AChE activity and the subsequent change in electrochemical reduction response of DTNB. Good relationship was obtained between the reduction current and pesticide concentration in the ranges of 5.0 × 10⁻⁷ to 1.0 × 10⁻¹² M with a detection limit of 7.5 × 10⁻¹³ M (S/N = 3). Moreover, the proposed protocol was successfully employed for the determination of methyl parathion in water and soil samples.     

Potentiometric stripping analysis of antimony based on carbon paste electrode modified with hexathia crown ether and rice husk

An electrochemical method based on potentiometric stripping analysis (PSA) employing a hexathia 18C6 (HT18C6) and rice husk (RH) modified carbon paste electrode (HT18C6–RH-CPE) has been proposed for the subnanomolar determination of antimony. The characterization of the electrode surface has been carried out by means of scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and chronocoulometry. By employing HT18C6–RH-CPE, a 12-fold enhancement in the PSA signal (dt/dE) was observed as compared to plain carbon paste electrode (PCPE). Under the optimized conditions, dt/dE (s V⁻¹) was proportional to the Sb(III) concentration in the range of 1.42 × 10⁻⁸ to 6.89 × 10⁻¹¹ M (r = 0.9944) with the detection limit (S/N = 3) of 2.11 × 10⁻¹¹ M. The practical analytical utilities of the modified electrode were demonstrated by the determination of antimony in pharmaceutical formulations, human hair, sea water, urine and blood serum samples. The prepared modified electrode showed several advantages, such as simple preparation method, high sensitivity, very low detection limit and excellent reproducibility. Moreover, the results obtained for antimony analysis in commercial and real samples using HT18C6–RH-CPE and those obtained by inductively coupled plasma-atomic emission spectrometry (ICP-AES) are in agreement at the 95% confidence level.     

Zeolite A functionalized with copper nanoparticles and graphene oxide for simultaneous electrochemical determination of dopamine and ascorbic acid

A novel Cu-zeolite A/graphene modified glassy carbon electrode for the simultaneous electrochemical determination of dopamine (DA) and ascorbic acid (AA) has been described. The Cu-zeolite A/graphene composites were prepared using Cu²⁺ functionalized zeolite A and graphene oxide as the precursor, and subsequently reduced by chemical agents. The composites were characterized by X-ray diffraction, Fourier transform infrared spectra and scanning electron microscopy. Based on the Cu-zeolite A/graphene-modified electrode, the potential difference between the oxidation peaks of DA and AA was over 200 mV, which was adequate for the simultaneous electrochemical determination of DA and AA. Also the proposed Cu-zeolite/graphene-modified electrode showed higher electrocatalytic performance than zeolite/graphene electrode or graphene-modified electrode. The electrocatalytic oxidation currents of DA and AA were linearly related to the corresponding concentration in the range of 1.0 × 10⁻⁷–1.9 × 10⁻⁵ M for DA and 2.0 × 10⁻⁵–2.0 × 10⁻⁴ M for AA. Detection limits (<!-- no-mfc -->S/N<!-- /no-mfc --> = 3) were estimated to be 4.1 × 10⁻⁸ M for DA and 1.1 × 10⁻⁵ M for AA, respectively.     

Simultaneous voltammetric determination of acetaminophen and tramadol using Dowex50wx2 and gold nanoparticles modified glassy carbon paste electrode

A glassy carbon paste electrode (GCPE) modified with a cation exchanger resin, Dowex50wx2 and gold nanoparticles (D50wx2–GNP–GCPE) has been developed for individual and simultaneous determination of acetaminophen (ACOP) and tramadol (TRA). The electrochemical behavior of both the molecules has been investigated employing cyclic voltammetry (CV), chronocoulometry (CC), electrochemical impedance spectroscopy (EIS) and adsorptive stripping square wave voltammetry (AdSSWV). The studies revealed that the oxidation of ACOP and TRA is facilitated at D50wx2–GNP–GCPE. Using AdSSWV, the method allowed simultaneous determination of ACOP and TRA in the linear working range of 3.34 × 10⁻⁸ to 4.22 × 10⁻⁵ M with detection limits of 4.71 × 10⁻⁹ and 1.12 × 10⁻⁸ M (S/N = 3) for ACOP and TRA respectively. The prepared modified electrode shows several advantages such as simple preparation method, long-time stability, ease of preparation and regeneration of the electrode surface by simple polishing and excellent reproducibility. The high sensitivity and selectivity of D50wx2–GNP–GCPE were demonstrated by its practical application in the determination of both ACOP and TRA in pharmaceutical formulations, urine and blood serum samples.     

Study of the electrochemical behavior of isorhamnetin on a glassy carbon electrode and its application

The electrochemical behavior of isorhamnetin (ISO) at a glassy carbon electrode was studied in a phosphate buffer solution (PBS) of pH 4.0 by cyclic voltammetry (CV) and differential pulse voltammetric method (DPV). A well-defined redox wave of ISO involving one electrons and one proton appeared. The electrode reaction is a reactant weak adsorption-controlled process with a charge transfer coefficient (α) of 0.586. Based on the understanding of the electrochemical process of ISO at the glassy carbon electrode, analysis of ISO can be realized. Under optimal conditions, the oxidation peak current showed linear dependence on the concentration of ISO in the range of 1.0 × 10⁻⁸ to 4.0 × 10⁻⁷ M and 1.0 × 10⁻⁶ to 1.0 × 10⁻⁵ M. The detection limit is 5.0 × 10⁻⁹ M. This method has been successfully applied to the detection of ISO in tablets.     

Ultrasensitive electrochemical sensor for p-nitrophenyl organophosphates based on ordered mesoporous carbons at low potential without deoxygenization

p-Nitrophenyl organophosphates (OPs) including paraoxon, parathion and methyl parathion, etc, are highly poisonous OPs, for which sensitive and rapid detection method is most needed. In this work, an ultrasensitive electrochemical sensor for the determination of p-nitrophenyl OPs was developed based on ordered mesoporous carbons (OMCs) modified glassy carbon electrode (GCE) (OMCs/GCE). The electrochemical behavior and reaction mechanism of p-nitrophenyl OPs at OMCs/GCE was elaborated by taking paraoxon as an example. Experimental conditions such as buffer pH, preconcentration potential and time were optimized. By using differential pulse voltammetry, the current response of the sensor at −0.085 V was linear with concentration within 0.01–1.00 μM and 1.00–20 μM paraoxon. Similar linear ranges of 0.015–0.5 μM and 0.5–10 μM were found for parathion, and 0.01–0.5 μM and 0.5–10 μM for methyl parathion. The low limits of detection were evaluated to be 1.9 nM for paraoxon, 3.4 nM for parathion and 2.1 nM for methyl parathion (S/N = 3). Common interfering species had no interference to the detection of p-nitrophenyl OPs. The sensor can be applicable to real samples measurement. Therefore, a simple, sensitive, reproducible and cost-effective electrochemical sensor was proposed for the fast direct determination of trace p-nitrophenyl OPs at low potential without deoxygenization.     

Electrodeposited nitrogen-doped graphene/carbon nanotubes nanocomposite as enhancer for simultaneous and sensitive voltammetric determination of caffeine and vanillin

A nitrogen-doped graphene/carbon nanotubes (NGR–NCNTs) nanocomposite was employed into the study of the electrochemical sensor via electrodeposition for the first time. The morphology and structure of NGR–NCNTs nanocomposite were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. Meanwhile, the electrochemical performance of the glassy carbon electrode (GCE) modified with electrodeposited NGR–NCNTs (ENGR–NCNTs/GCE) towards caffeine (CAF) and vanillin (VAN) determination was demonstrated by cyclic voltammetry (CV) and square wave voltammetry (SWV). Under optimal condition, ENGR–NCNTs/GCE exhibited a wide linearity of 0.06–50 μM for CAF and 0.01–10 μM for VAN with detection limits of 0.02 μM and 3.3 × 10⁻³ μM, respectively. Furthermore, the application of the proposed sensor in food products was proven to be practical and reliable. The desirable results show that the ENGR–NCNTs nanocomposite has promising potential in electrocatalytic biosensor application.     

An enzymeless organophosphate pesticide sensor using Au nanoparticle-decorated graphene hybrid nanosheet as solid-phase extraction

A sensitive enzymeless organophosphate pesticides (OPs) sensor is fabricated by using Au nanoparticles (AuNPs) decorated graphene nanosheets (GNs) modified glassy carbon electrode as solid phase extraction (SPE). Such a nanostructured composite film, combining the advantages of AuNPs with two dimensional GNs, dramatically facilitates the enrichment of nitroaromatic OPs onto the surface and realizes their stripping voltammetric detection of OPs by using methyl parathion (MP) as a model. The stripping voltammetric performances of captured MP were evaluated by cyclic voltammetric and square-wave voltammetric analysis. The combination of the nanoassembly of AuNPs-GNs, SPE, and stripping voltammetry provides a fast, simple, and sensitive electrochemical method for detecting nitroaromatic OPs. The stripping analysis is highly linear over the MP concentration ranges of 0.001-0.1and 0.2-1.0 μg mL⁻¹ with a detection limit of 0.6 ng mL⁻¹. This designed enzymeless sensor exhibits good reproducibility and acceptable stability.     

Study on electrochemical behavior of tryptophan at a glassy carbon electrode modified with multi-walled carbon nanotubes embedded cerium hexacyanoferrate

Electrochemical behavior of cerium hexacyanoferrate (CeHCF) incorporated on multi-walled carbon nanotubes (MWNTs) modified GC electrode is investigated by scanning electron microscopy (SEM) and electrochemical techniques. The CeHCF/MWNT/GC electrode showed potent electrocatalytic activity toward the electrochemical oxidation of tryptophan in phosphate buffer solution (pH 7.0) with a diminution of the overpotential of 240 mV. The anodic peak currents increased linearly with the concentration of tryptophan in the range of 2.0 × 10⁻⁷ to 1.0 × 10⁻⁴ M with a detection limit of 2.0 × 10⁻⁸ M (at a S/N = 3). And the determination of tryptophan in pharmaceutical samples was satisfactory.     

A novel bimediator amperometric sensor for electrocatalytic oxidation of gallic acid and reduction of hydrogen peroxide

A novel bimediator amperometric sensor is fabricated for the first time by surface modification of graphite electrode with thionine (TH) and nickel hexacyanoferrate (NiHCF). The electrochemical behavior of the TH/NiHCF bimediator modified electrode was characterized by cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The TH/NiHCF bimediator modified electrode exhibited a pair of distinct redox peaks for NiHCF and TH with formal potentials of 0.33 V and −0.27 V vs. SCE at a scan rate of 50 mV s⁻¹ in 0.1 M NaNO₃ and 0.1 M NH₄NO₃ respectively. The electrocatalytic activity of the bimediator modified electrode towards oxidation of gallic acid with NiHCF and reduction of hydrogen peroxide with TH was evaluated and it was observed that the modified electrode showed an electrocatalytic activity towards the oxidation of gallic acid in the concentration range of 4.99 × 10⁻⁶–1.20 × 10⁻³ M with a detection limit of 1.66 × 10⁻⁶ M (S/N = 3) and reduction of H₂O₂ in the concentration range of 1.67 × 10⁻⁶–1.11 × 10⁻³ M with a detection limit of 5.57 × 10⁻⁷ M (S/N = 3). The bimediator modified electrode was found to exhibit good stability and reproducibility.     

Bifunctional polydopamine@Fe3O4 core–shell nanoparticles for electrochemical determination of lead(II) and cadmium(II)

The present paper has focused on the potential application of the bifunctional polydopamine@Fe₃O₄ core–shell nanoparticles for development of a simple, stable and highly selective electrochemical method for metal ions monitoring in real samples. The electrochemical method is based on electrochemical preconcentration/reduction of metal ions onto a polydopamine@Fe₃O₄ modified magnetic glassy carbon electrode at −1.1 V (versus SCE) in 0.1 M pH 5.0 acetate solution containing Pb²⁺ and Cd²⁺ during 160 s, followed by subsequent anodic stripping. The proposed method has been demonstrated highly selective and sensitive detection of Pb²⁺ and Cd²⁺, with the calculated detection limits of 1.4 × 10⁻¹¹ M and 9.2 × 10⁻¹¹ M. Under the optimized conditions, the square wave anodic stripping voltammetry response of the modified electrode to Pb²⁺ (or Cd²⁺) shows a linear concentration range of 5.0–600 nM (or 20–590 nM) with a correlation coefficient of 0.997 (or 0.994). Further, the proposed method has been performed to successfully detect Pb²⁺ and Cd²⁺ in aqueous effluent.     

Square wave adsorptive cathodic stripping voltammetry automated by sequential injection analysis Potentialities and limitations exemplified by the determination of methyl parathion in water samples

This paper describes the development and evaluation of a sequential injection method to automate the determination of methyl parathion by square wave adsorptive cathodic stripping voltammetry exploiting the concept of monosegmented flow analysis to perform in-line sample conditioning and standard addition. Accumulation and stripping steps are made in the sample medium conditioned with 40 mmol L⁻¹ Britton-Robinson buffer (pH 10) in 0.25 mol L⁻¹ NaNO₃. The homogenized mixture is injected at a flow rate of 10 μL s⁻¹ toward the flow cell, which is adapted to the capillary of a hanging drop mercury electrode. After a suitable deposition time, the flow is stopped and the potential is scanned from −0.3 to −1.0 V versus Ag/AgCl at frequency of 250 Hz and pulse height of 25 mV. The linear dynamic range is observed for methyl parathion concentrations between 0.010 and 0.50 mg L⁻¹, with detection and quantification limits of 2 and 7 μg L⁻¹, respectively. The sampling throughput is 25 h⁻¹ if the in line standard addition and sample conditioning protocols are followed, but this frequency can be increased up to 61 h⁻¹ if the sample is conditioned off-line and quantified using an external calibration curve. The method was applied for determination of methyl parathion in spiked water samples and the accuracy was evaluated either by comparison to high performance liquid chromatography with UV detection, or by the recovery percentages. Although no evidences of statistically significant differences were observed between the expected and obtained concentrations, because of the susceptibility of the method to interference by other pesticides (e.g., parathion, dichlorvos) and natural organic matter (e.g., fulvic and humic acids), isolation of the analyte may be required when more complex sample matrices are encountered.     

Analysis of parabens in cosmetics by low pressure liquid chromatography with monolithic column and chemiluminescent detection

This paper presents an application of chromatographic separation based on an ultra-short monolithic column and chemiluminescent detection in an FIA type instrument manifold for the determination of four paraben mixtures: methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP). The separation is achieved in 150 s using two consecutive carriers: first 12% ACN:water that changes 75 s after injection to 27% ACN:water. The detection is based on the oxidation of the hydrolysis product of parabens, p-hydroxybenzoic acid, with Ce(IV) in the presence of Rhodamine 6G which evokes chemiluminescence of sufficient intensity to enable a sensitive determination of these species. After optimization of the variables involved, the analytical method is characterized, displaying the following values for concentration ranges, detection limits and precision, as relative standard deviation at low concentration (0.15 mg l⁻¹)—MP: from 9.9 × 10⁻⁷ to 3.3 × 10⁻⁴ M; 1.9 × 10⁻⁸; 5.6%; EP: from 9.0 × 10⁻⁷ to 3.3 × 10⁻⁴ M; 2.8 × 10⁻⁸; 3.5%; PP: from 8.3 × 10⁻⁷ to 9.9 × 10⁻⁵ M; 2.3 × 10⁻⁸; 4.2%; and BP: from 7.7 × 10⁻⁷ to 9.9 × 10⁻⁵ M; 4.2 × 10⁻⁸ M; 6.2%. The method was applied and validated satisfactorily for the determination of these parabens in cosmetic samples, comparing the results against a liquid chromatography reference method.     

Electrochemical study of nitrobenzene reduction using novel Pt nanoparticles/macroporous carbon hybrid nanocomposites

Novel Pt nanoparticles (PN) ensemble on macroporous carbon (MPC) hybrid nanocomposites (PNMPC) were prepared through a rapidly and simple one-step microwave-assisted heating procedure. The obtained PNMPC was characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and electrochemical methods. The electrochemical reduction of nitrobenzene (NB) was thoroughly investigated at the PNMPC modified glassy carbon (GC) electrode, and the catalytic rate constant was calculated to be 3.14 × 10⁴ M⁻¹ s⁻¹ for NB. A sensitive NB sensor was developed based on the PNMPC/GC electrode, which showed a wide linear range (1–200 μM), low detection limit (50 nM), high sensitivity (6.93 μA μM⁻¹), excellent anti-interference ability and good stability. And moreover, the electrode was successfully applied to the determination of NB in real samples.     

An electrochemical sensor prepared by sonochemical one-pot synthesis of multi-walled carbon nanotube-supported cobalt nanoparticles for the simultaneous determination of paracetamol and dopamine

Multi-walled carbon nanotubes (MWCNTs) functionalized by cobalt nanoparticles were obtained using a single step chemical deposition method in an ultrasonic bath. The composite material was characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The electroactivity of the cobalt-functionalized MWCNTs was assessed in respect to the electrooxidation of paracetamol (PAR) and dopamine (DA). It was found that the carbon nanotube supported cobalt nanoparticles have significantly higher catalytic properties. The proposed electrode has been applied for the simultaneous determination of PAR and DA. The modified electrode could resolve the overlapped voltammetric waves of PAR and DA into two well-defined voltammetric peaks with peak to peak separation of about 203 mV. On the other hand, the presence of potential drug interfering compounds AA and UA did not affect the voltammetric responses of PAR and DA. The current of oxidation peaks showed a linear dependent on the concentrations of PAR and DA in the range of 5.2 × 10⁻⁹–4.5 × 10⁻⁷ M (R² = 0.9987) and 5.0 × 10⁻⁸–3.0 × 10⁻⁶ M (R² = 0.9999), respectively. The detection limits of 1.0 × 10⁻⁹ M and 1.5 × 10⁻⁸ M were obtained for PAR and DA, respectively. The proposed electrode showed good stability (peak current change: 4.9% with and RSD of 2.6% for PAR; 5.5% with and RSD of 3.0% for DA over 3 weeks), reproducibility (RSD 2.3% for PAR and RSD 1.5% for DA), repeatability (RSD 2.25% for PAR and RSD 2.50% for DA) and high recovery (99.7% with an RSD of 1.3% for PAR; 100.8% with an RSD of 1.8% for DA). The proposed method was successfully applied to the determination of PAR and DA in pharmaceuticals.     

Seed-mediated synthesis of copper nanoparticles on carbon nanotubes and their application in nonenzymatic glucose biosensors

In this paper, for the first time, Cu nanoparticles (CuNPs) were prepared by seed-mediated growth method with Au nanoparticles (AuNPs) playing the role of seeds. Carbon nanotubes (CNTs) and AuNPs were first dropped on the surface of glassy carbon (GC) electrode, and then the electrode was immersed into growth solution that contained CuSO₄ and hydrazine. CuNPs were successfully grown on the surface of the CNTs. The modified electrode showed a very high electrochemical activity for electrocatalytic oxidation of glucose in alkaline medium, which was utilized as the basis of the fabrication of a nonenzymatic biosensor for electrochemical detection of glucose. The biosensor can be applied to the quantification of glucose with a linear range covering from 1.0 × 10⁻⁷ to 5 × 10⁻³ M and a low detection limit of 3 × 10⁻⁸ M. Furthermore, the experiment results also showed that the biosensor exhibited good reproducibility and long-term stability, as well as high selectivity with no interference from other oxidable species.     

Simultaneous determination of epinephrine, uric acid and xanthine in the presence of ascorbic acid using an ultrathin polymer film of 5-amino-1,3,4-thiadiazole-2-thiol modified electrode

This paper describes the simultaneous determination of epinephrine (EP), uric acid (UA) and xanthine (XN) in the presence of ascorbic acid (AA) using electropolymerized ultrathin film of 5-amino-1,3,4-thiadiazole-2-thiol (p-ATT) modified glassy carbon (GC) electrode in 0.2 M phosphate buffer solution (pH 5). Although bare GC electrode resolves the voltammetric signals of AA and XN, it fails to resolve the voltammetric signals of EP and UA in a mixture. However, the p-ATT modified electrode not only separates the voltammetric signals of AA, EP, UA and XN with potential difference of 150, 120 and 400 mV between AA-EP, EP-UA and UA-XN, respectively but also shows higher oxidation current for these molecules. The p-ATT modified electrode exhibits excellent selectivity towards the oxidation of EP, UA and XN in the presence of 40-fold higher concentration of AA. Further, the p-ATT modified electrode was also used for the selective determination of EP in the presence of 40-fold higher concentrations of AA, UA and XN. Using amperometric method, we achieved the lowest detection of 40 nM EP and 60 nM each UA and XN. The amperometric current response was increased linearly with increasing EP concentration in the range of 4.0 × 10⁻⁸ to 4.0 × 10⁻⁵ M and the detection limit was found to be 27 × 10⁻¹¹ M (S/N = 3). The practical application of the present modified electrode was demonstrated by determining the concentration of EP in epinephrine tartrate injection and XN in human urine samples.     

para-Sulfonatocalix[6]arene-modified silver nanoparticles electrodeposited on glassy carbon electrode: Preparation and electrochemical sensing of methyl parathion

In this paper, a new electrochemical sensor, based on modified silver nanoparticles, was fabricated using one-step electrodeposition approach. The para-sulfonatocalix[6]arene-modified silver nanoparticles coated on glassy carbon electrode (pSC₆-Ag NPs/GCE) was characterized by attenuated total reflection IR spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), etc. The pSC₆ as the host are highly efficient to capture organophosphates (OPs), which dramatically facilitates the enrichment of nitroaromatic OPs onto the electrochemical sensor surface. The combination of the host-guest supramolecular structure and the excellent electrochemical catalytic activities of the pSC₆-Ag NPs/GCE provides a fast, simple, and sensitive electrochemical method for detecting nitroaromatic OPs. In this work, methyl parathion (MP) was used as a nitroaromatic OP model for testing the proposed sensor. In comparison with Ag NPs-modified electrode, the cathodic peak current of MP was amplified significantly. Differential pulse voltammetry was used for the simultaneous determination of MP. Under optimum conditions, the current increased linearly with the increasing concentration of MP in the range of 0.01-80 μM, with a detection limit of 4.0 nM (S/N = 3). The fabrication reproducibility and stability of the sensor is better than that of enzyme-based electrodes. The possible underlying mechanism is discussed.     

Synthesis of Cu-mediated nano-sized salbutamol-imprinted polymer and its use for indirect recognition of ultra-trace levels of salbutamol

Cu²⁺-mediated salbutamol-imprinted polymer nanoparticles, synthesized by precipitation polymerization, were mixed with graphite powder and n-eicosane in order to fabricate a modified carbon paste electrode. This electrode was then applied for indirect differential pulse voltammetry determination of salbutamol. In the presence of Cu²⁺ ions, the formed Cu²⁺–salbutamol complex was adsorbed in to the pre-designed cavities of the MIP particles, situated on the electrode surface. Since the electrochemical signal of salbutamol was intrinsically small, the oxidation peak of the participant Cu²⁺, after reduction step, was recorded and used as an indication of salbutamol amount, adsorbed in the electrode. Different variables influencing the sensor performance were studied and the best conditions were chosen for the determination purpose. Correlation between the sensor response to salbutamol and its concentration was linear in the range of 1.0 × 10⁻⁹–5.5 × 10⁻⁸ M. Detection limit was calculated equal to 6.0 × 10⁻¹⁰ M (S/N). Five replicated determination of salbutamol (1 × 10⁻⁸ M) resulted in standard error of 3.28%, meaning a satisfactory precision of the determination method. The prepared sensor was applied for real sample analysis. In order to minimize the interference effect, the synthesized polymer was successfully used as a solid phase sorbent for salbutamol extraction, before analysis of real samples by the developed sensor.