Selective electrochemical molecular recognition of benzenediol isomers using molecularly imprinted TiO2 film electrodes

In this paper, selective recognition of benzenediol isomers was studied using molecularly imprinted TiO₂ film formed on a graphitic electrode. The imprinting process was investigated in detail using IR. The electrode process for p-hydroquinone follows a E_rC_r mechanism. The cavities formed by p-phthalic acid have good selectivity toward p-hydroquinone among the isomers. The complex ratio between p-hydroquinone and binding sites was estimated to be 1:2 with an apparent equilibrium constant of 2.98×10⁶ l² mol⁻². For o-hydroquinone and m-benzenediol, the ratio decreased to 1:1 with an apparent equilibrium constant of 1.20×10³ and 1.35×10³ l mol⁻¹. The apparent complexing ratio and equilibrium constants could shed some insight on the nature of isomeric selectivity of the recognition sites with respect to different isomers of benzenediol. The cavities designed by o-phthalic acid present good selectivity toward o-hydroquinone.     

Detection of nicotine based on molecularly imprinted TiO2-modified electrodes

Amperometric detection of nicotine (NIC) was carried out on a titanium dioxide (TiO₂)/poly(3,4-ethylenedioxythiophene) (PEDOT)-modified electrode by a molecular imprinting technique. In order to improve the conductivity of the substrate, PEDOT was coated onto the sintered electrode by in situ electrochemical polymerization of the monomer. The sensing potential of the NIC-imprinted TiO₂ electrode (ITO/TiO₂[NIC]/PEDOT) in a phosphate-buffered saline (PBS) solution (pH 7.4) containing 0.1 M KCl was determined to be 0.88 V (vs. Ag/AgCl/saturated KCl). The linear detection range for NIC oxidation on the so-called ITO/TiO₂[NIC]/PEDOT electrode was 0-5 mM, with a sensitivity and limit of detection of 31.35 μA mM⁻¹ cm⁻² and 4.9 μM, respectively. When comparing with the performance of the non-imprinted one, the sensitivity ratio was about 1.24. The sensitivity enhancement was attributed to the increase in the electroactive area of the imprinted electrode. The at-rest stability of the ITO/TiO₂[NIC]/PEDOT electrode was tested over a period of 3 days. The current response remained about 85% of its initial value at the end of 2 days. The ITO/TiO₂[NIC]/PEDOT electrode showed reasonably good selectivity in distinguishing NIC from its major interferent, (−)-cotinine (COT). Moreover, scanning electrochemical microscopy (SECM) was employed to elucidate the surface morphology of the imprinted and non-imprinted electrodes using Fe(CN)₆³⁻/Fe(CN)₆⁴⁻ as a redox probe on a platinum tip. The imprinted electrode was further characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR).     

New triiodomercurate-modified carbon paste electrode for the potentiometric determination of mercury

A new tetrazolium-triiodomercurate-modified carbon paste electrode has been described for the sensitive and selective determination of mercury. The electrode shows a stable, near-Nernstian response for 1×10⁻³ to 6×10⁻⁶ M [HgI₃]⁻ at 25 °C over the pH range of 4.0-9.0, with an anionic slope of 55.5±0.4 mV. The lower detection limit is 4×10⁻⁶ M with a fast response time of 30-50 s. Selectivity coefficients of a number of interfering anions and iodo complexes of some metal ions have been estimated. The interference from many of the investigated ions is negligible. The determination of 1-200 μg/ml of mercury in aqueous solutions shows an average recovery of 98.5% and a mean relative standard deviation of 1.6% at 50.0 μg/ml. The direct determination of mercury in spiked wastewater, metal amalgams and dental alloy gave results that compare favorably with those obtained by the cold vapor atomic absorption spectrometric method. Potentiometric titration of mercury and phenylmercury acetate with standard potassium iodide has been monitored using the developed triiodomercurate-carbon paste electrode (CPE) as an end point indicator electrode.     

Synthesis of a novel bistriazene reagent 4,4′-bis[3-(4-phenylthiazol-2-yl)triazenyl]biphenyl and its highly sensitive color reaction with mercury(II)

We report the synthesis of a novel bistriazene, 4,4′-bis(3-(4-phenylthiazol-2-yl)triazenyl)biphenyl (BPTTBP), and its highly sensitive color reaction with Hg²⁺. The new reagent was synthesized in good yield by coupling 2-amino-4-phenylthiazole with 4,4′-biphenyldiamine bisdiazonium salt. Using a blend of surfactants N-cetylpyridinium chloride (CPC) and polyethylene glycol n-octanoic phenyl ether (OP) as a micelle sensitizer, the red colored reagent assembles with Hg²⁺ in pH 9.8 borate buffer according to a 1:1 stoichiometry, forming a blue oligomeric/polymeric chelating complex with a high apparent stability constant (1.1 × 10⁸ M⁻¹). Whereas the maximum absorption of reagent occurs at 510 nm with an extinct coefficient of 1.35 × 10⁴ M⁻¹ cm⁻¹, the complex absorbs at 611 nm, with an apparent extinct coefficient of 1.04 × 10⁵ M⁻¹ cm⁻¹. Beer's law is obeyed in the range of 0-15 μg/25 mL Hg²⁺, and Sandell's sensitivity is 1.92 × 10⁻³ μg/cm². In the presence of thiourea and Na₄P₂O₇ as masking agents, the method was found free from interferences of foreign ions commonly occurring with mercury. The optimized protocol has been successfully applied to spectrophotometric determination of mercury in waste water samples. The features of the new reagent associated with its special structure were discussed, and an unprecedented “domino effect” was proposed to account for its unique chelating stoichiometry with Hg²⁺.     

A validated stripping voltammetric procedure for quantification of the anti-hypertensive and benign prostatic hyperplasia drug terazosin in tablets and human serum

The electrochemical behavior of terazosin at the hanging mercury drop electrode was studied in Britton-Robinson buffer (pH 2-11), acetate buffer (4.5-5.5), and in 0.1 M solution of each of sodium sulfate, sodium nitrate, sodium perchlorate and potassium chloride as supporting electrolytes. The square-wave adsorptive cathodic stripping voltammogram of terazosin exhibited a single well-defined two-electron irreversible cathodic peak which may be attributed to the reduction of CO double bond of the drug molecule. A fully validated, simple, high sensitive, precise and inexpensive square-wave adsorptive cathodic stripping voltammetric procedure was described for determination of terazosin in bulk form, tablets and human serum. A mean recovery for 1×10⁻⁸ M terazosin in bulk form, following preconcentration onto the hanging mercury drop electrode for 60 s at a −1.0 V (versus Ag/AgCl/KCl_s), of 99±0.7% (n=5) was obtained. Limits of detection (LOD) and quantitation (LOQ) of 1.5×10⁻¹¹ and 5×10⁻¹¹ M bulk terazosin were achieved, respectively. The proposed procedure was successfully applied to determination of the drug in its Itrin^® tablets and human serum samples. The achieved LOD and LOQ of the drug in human serum samples were 5.3×10⁻¹¹ and 1.8×10⁻¹⁰ M THD, respectively. The pharmacokinetic parameters of the drug in human plasma were estimated as: C_max=77.5 ng ml⁻¹, t_max=1.75 h, AUC_0-t=602.3 ng h ml⁻¹, K_e=0.088 h⁻¹ and t_1/2=11.32 h) which are favorably compared with those reported in literature.     

Cathodic adsorptive stripping voltammetric determination of uranium (VI) complexed with 2, 6-pyridinedicarboxylic acid

Uranium (VI) (U(VI)) forms a complex with dipicolinic acid (2, 6-pyridinedicarboxylic acid).This complex can be used for a highly sensitive and selective determination of uranium by adsorptive cathodic stripping voltammetry (ACSV) using a hanging mercury drop electrode (HMDE) as working electrode. Influence of effective parameters such as pH, concentration of ligand, accumulation potential and accumulation time on the sensitivity and selectivity were studied. The detection limit (3σ of the blank value) obtained under the optimal experimental conditions is 0.27 × 10⁻⁹ M after 150 s of the accumulation time. The peak current is proportional to the concentration of U(VI) in the range of 1 × 10⁻⁹ to 1.2 × 10⁻⁷ M. The relative standard deviation of 2.5% at the 3.5 × 10⁻⁸ M level was obtained. The interference of some metal ions and anions were studied. The application of this method was tested in the determination of uranium in synthetic and natural water samples.     

Schiff bases as cadmium(II) selective ionophores in polymeric membrane electrodes

The construction and performance characteristics of polymeric membrane electrodes based on two neutral ionophores, N,N′-[bis(pyridin-2-yl)formylidene]butane-1,4-diamine (S₁) and N-(2-pyridinylmethylene)-1,2-benzenediamine (S₂) for quantification of cadmium ions, are described. The influences of membrane compositions on the potentiometric response of the electrodes have been found to substantially improve the performance characteristics. The best performance was obtained with the electrode having a membrane composition (w/w) of (S₁) (2.15%):PVC (32.2%):o-NPOE (64.5%):KTpClPB (1.07%). The proposed electrode exhibits Nernstian response in the concentration range of 7.9 × 10⁻⁸ to 1.0 × 10⁻¹ M Cd²⁺ with limit of detection 5.0 × 10⁻⁸ M, performs satisfactorily over wide pH range (2.0-8.0) with a fast response time (10 s). The sensor has been found to work satisfactorily in partially non-aqueous media up to 30% (v/v) content of methanol, ethanol and acetonitrile and could be used for a period of 2 months. The analytical usefulness of the proposed electrode has been evaluated by its application in the determination of cadmium in real samples. The practical utility of the membrane electrode has also been observed in the presence of surfactants.     

A highly selective mercury electrode based on a diamine donor ligand

(H₂NCHMeCH₂NH₂)(H₂O)₂HgCl₂ (I) was synthesised, characterised and used for the fabrication of a potentiometric sensor for Hg²⁺ metal ions. Membrane having I as electroactive material, sodium tetraphenyl borate (NaTPB) as an anion excluder, dibutylamine (DBA) as plasticizer in PVC matrix in the percentage ratio of 10:3:150:150 (I:NaTPB:DBA:PVC) (w/w) exhibits a linear response to Hg²⁺ ions in a concentration range of 1.25 × 10⁻⁵ to 1.0 × 10⁻¹ M having a detection limit of 8.9 × 10⁻⁶ with a slope of 25 ± 0.1 mV over the pH range 6.6-9.3. Selectivity coefficients for Hg(II) relative to a number of interfering ions were investigated. The electrode is highly selective for Hg²⁺ ions over a large number of mono-, bi-, and trivalent cations. Normal interferents like Ag⁺ and Cd²⁺ do not interfere in the working of the electrode. The electrode has also been used successfully in mixtures having a 10% (v/v) methanol and acetone content without showing any considerable change in working concentration range or slope. These electrodes have been found to be chemically inert showing a fast response time of 10 s and were used over a period of 4 months with good reproducibility (s = ±0.2). The electrode was used for determination of mercury in binary mixtures with 100% recovery and thus the proposed sensor can be used for real sample analysis.     

Construction of a novel molecularly imprinted sensor for the determination of O,O-dimethyl-(2,4-dichlorophenoxyacetoxyl)(3′-nitrophenyl)methinephosphonate

A novel voltammetric sensor for O,O-dimethyl-(2,4-dichlorophenoxyacetoxyl)(3′-nitrophenyl)methinephosphonate (Phi-NO₂) based on molecularly imprinted polymer (MIP) film electrode is constructed by using sol-gel technology. The sensor responds linearly to Phi-NO₂ over the concentration range of 2.0 × 10⁻⁵ to 1.0 × 10⁻⁸ mol L⁻¹ and the detection limit is 1.0 × 10⁻⁹ mol L⁻¹ (S/N = 3). This sensor provides an efficient way for eliminating interferences from coexisting substances in the solution. The high sensitivity, selectivity and stability of the sensor demonstrates its practical application for a simple and rapid determination of Phi-NO₂ in cabbage samples.     

Langmuir-Blodgett film of p-tert-butylthiacalix[4]arene modified glassy carbon electrode as voltammetric sensor for the determination of Hg(II)

The π-A isotherms and UV-vis spectra of the transferred films suggested that the monolayer of p-tert-butylthiacalix[4]arene can coordinate with Hg²⁺ at the air-water surface. From these observations, a glassy carbon electrode coated with Langmuir-Blodgett film of p-tert-butylthiacalix[4] arene as a new voltammetric sensor is designed for the determination of trace amounts of Hg²⁺. Compared with bare glassy carbon electrode and modified glassy carbon electrode using direct coating method, the Langmuir-Blodgett film-modified electrode can greatly improve the measuring sensitivity of Hg²⁺. Under the selected conditions, the Langmuir-Blodgett film-modified electrode in 0.1 mol L⁻¹ H₂SO₄ + 0.01 mol L⁻¹ KCl solution shows a linear voltammetric response for Hg²⁺ in the range of 5.0 × 10⁻¹⁰ to 1.5 × 10⁻⁷ mol L⁻¹, with a detection limit of 2.0 × 10⁻¹⁰ mol L⁻¹. The proposed method was also applied to determine Hg²⁺ in water samples (tap, lake and river water). In addition, the fabricated electrode exhibited a distinct advantage of simple preparation, non-toxicity, good reproducibility and good stability.     

Sensitized extraction spectrophotometric determination of Hg(II) with dithizone after its flotation as ion-associate using iodide and ferroin

This paper describes a simple and highly selective method for the separation, preconcentration and spectrophotometric determination of extremely low concentration of mercury. The method is based on the flotation of an ion-associate of HgI₄²⁻ and ferroin between aqueous and n-heptane interface at pH 5. The ion-associate was then separated and treated with ammonia and dithizone solutions to extract only the mercury chelate with CH₂Cl₂. The measurement is feasible when the volume of the water sample containing Hg(II) was varied over 50-800 ml. Beer's law was obeyed over the concentration range of 8 × 10⁻⁹ to 1.6 × 10⁻⁷ mol l⁻¹ with an apparent molar absorptivity of 6.53 × 10⁶ l mol⁻¹ cm⁻¹ for a 500 ml aliquot of the water sample. The detection limit (n = 7) was 5.0 × 10⁻¹⁰ mol l⁻¹ and the R.S.D. (n = 5) for 8.0 × 10⁻⁷ mol l⁻¹ of Hg(II) was 3.7%. A notable advantage of the method is that the determination of Hg(II) is free from the interference of almost all cations and anions found in the environmental and waste water samples. The determination of Hg(II) in tap, synthetic sea water and human hair samples was carried out by the present method and cold vapor atomic absorption spectrometry (CV-AAS). The results were satisfactorily comparable so that the applicability of the proposed method was confirmed to the real samples.     

A strategy for improving the sensitivity of molecularly imprinted electrochemical sensors based on catalytic copper deposition

A novel method to improve the sensitivity of molecularly imprinted polymer sensors was developed. Oxytetracycline (OTC), which was selected as the template molecule, was first rebound to the imprinted cavities. Gold nanoparticles were then labeled with the amino groups of OTC molecules via electrostatic adsorption and non-covalent interactions. Copper ions were catalytically reduced by the gold nanoparticles, and copper was deposited onto the electrode. The deposited copper was electrochemically dissolved, and its oxidative currents were recorded by differential pulse voltammetry (DPV). OTC could be determined indirectly within the concentration range of 3.0 × 10⁻¹⁰ to 1.5 × 10⁻⁷ mol L⁻¹ with a detection limit of 6.8 × 10⁻¹¹ mol L⁻¹.     

Determination of Hg on poly(vinylferrocenium) (PVF)-modified platinum electrode

A new surface based on poly(vinylferrocenium) (PVF⁺)-modified platinum electrode was developed for determination of Hg²⁺ ions in aqueous solutions. The polymer was electrodeposited on platinum electrode by constant potential electrolysis as PVF⁺ClO₄⁻. Cl⁻ ions were then attached to the polymer matrix by anion exchange and the modified electrode was dipped into Hg²⁺ solution. Hg²⁺ was preconcentrated at the polymer matrix by adsorption and also complexation reaction with Cl⁻. Detection of Hg²⁺ was carried out by differential pulse anodic stripping voltammetry (DPASV) after reduction of Hg²⁺. Mercury ions as low as 5 × 10⁻¹⁰ M could be detected with the prepared electrode and the relative standard deviation was calculated as 6.35% at 1 × 10⁻⁶ M concentration (n = 6). Interferences of Ag⁺, Pb²⁺ and Fe³⁺ ions were also studied at two different concentration ratios with respect to Hg²⁺. The developed electrode was applied to the determination of Hg²⁺ in water samples.     

Linear polyamines as carriers in thiocyanate-selective membrane electrodes

The polyamines, octyl-[2-(2-octylamino-ethylamino)-ethyl]-amine (L¹) and octyl-{2-[2-(2-octylamino-ethylamino)-ethylamino]-ethyl}-amine (L²), have been used as anion ionophores in PVC-based membrane ion-selective electrodes. Different electrodes were prepared containing L¹, or L², and o-nitrophenyl octyl ether (NPOE) or bis(2-ethylhexyl)sebacate (DOS) as plasticizers. The response of the electrodes was tested in two different buffers, HEPES-KOH (pH 7) and MES-KOH (pH 5.6). Electrodes containing L¹ and L² with NPOE (E1 and E2, respectively) showed a Nernstian response for thiocyanate with a good response time. The detection limit, linear range and slope for electrode E1 were 3.8 × 10⁻⁶ mol dm⁻³, 1 × 10⁻⁵ to 1 × 10⁻¹ mol dm⁻³ and −57.2 mV decade⁻¹ at pH 5.6 and 4.47 × 10⁻⁶ mol dm⁻³, 1.95 × 10⁻⁵ to 1 × 10⁻¹ mol dm⁻³ and −58.1 mV decade⁻¹ at pH 7.0. For electrode E2 the detection limit, linear range and slope found were 2.63 × 10⁻⁶ mol dm⁻³, 7.94 × 10⁻⁶ to 1 × 10⁻¹ mol dm⁻³ and −58.5 mV decade⁻¹ at pH 5.6 and 1.23 × 10⁻⁵ mol dm⁻³, 7.95 × 10⁻⁵ to 1 × 10⁻¹ mol dm⁻³ and −46.0 mV decade⁻¹ at pH 7. In contrast, electrodes containing DOS as plasticizers gave only response at pH 5.6 (detection limit, linear range and slope at pH 5.6 were 3.16 × 10⁻⁵ mol dm⁻³, 1 × 10⁻⁴ to 1 × 10⁻¹ mol dm⁻³ and −52.6 mV decade⁻¹). Selectivity coefficients for different anions with respect to thiocyanate were calculated. The electrode E2 at pH 5.6 was also used for the determination of SCN⁻ by potentiometric titrations with Ag⁺ ions with good results. The electrode E2 was also used to determine concentrations of thiocyanate in biological samples.     

Electrochemical determination of L-phenylalanine at polyaniline modified carbon electrode based on β-cyclodextrin incorporated carbon nanotube composite material and imprinted sol-gel film

A sensitive and selective electrochemical sensor based on a polyaniline modified carbon electrode for the determination of l-phenylalanine has been proposed by utilizing β-cyclodextrin (β-CD) incorporated multi-walled carbon nanotube (MWNT) and imprinted sol-gel film. The electrochemical behavior of the sensor towards l-phenylalanine was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric i-t curve. The surface morphologies of layer-by-layer assembly electrodes were displayed by scanning electron microscope (SEM). The response mechanism of the imprinted sensor for l-phenylalanine was based on the inclusion interaction of β-CD and molecular recognition capacity of the imprinted film for l-phenylalanine. A linear calibration plot was obtained covering the concentration range from 5.0 × 10⁻⁷ to 1.0 × 10⁻⁴ mol L⁻¹ with a detection limit of 1.0 × 10⁻⁹ mol L⁻¹. With excellent sensitivity, selectivity, stability, reproducibility and recovery, the electrochemical imprinted sensor was used to detect l-phenylalanine in blood plasma samples successfully.     

Study of beta-cyclodextrin/fluorinated trimethyl ammonium bromide surfactant inclusion complex by fluorinated surfactant ion selective electrode

The construction and performance of a liquid membrane electrode responsive to N-(1,1,2,2-tetrahydroperfluorooctyl)-N,N,N-trimethylammonium bromide (FTABr) and its use for the study of β-cyclodextrin/fluorinated surfactant inclusion complex is described. The electrode is based on the use of tetrahydroperfluorooctyltrimethylammonium-tetraphenylborate ion pair as electro active material in polyvinyl chloride (PVC) matrix plasticized using 2-Nitrophenyl octyl ether (NPOE). The electrode exhibits a fast, stable, reproducible and “Nernstian” response (59 ± 2 mV) for FTABr over the concentration range of 10⁻⁵ to 2 × 10⁻³ mol L⁻¹ at 298 K. The lowest detection limit is 2 × 10⁻⁶ mol L⁻¹ and the response time is around 20-30 s. The validity of the electrode, for detection of fluorinated surfactant ions and hence to carry out electrochemical measurements to study micellization of fluorinated surfactant, is verified by comparing the critical micelle concentration (cmc) value of FTABr obtained by using the electrode, with that obtained by surface tension measurements. Association constant K for β-cyclodextrin/FTABr complex is evaluated from the potentiometric measurements carried out using this electrode and is observed to be ∼1.26 × 10⁵. The results suggest that β-cyclodextrin forms an equimolar association complex with the FTA⁺ surfactant ion.     

Comparison of pyrimethanil-imprinted beads and bulk polymer as stationary phase by non-linear chromatography

A pyrimethanil-imprinted polymer (P1) was prepared by iniferter-mediated photografting a mixture of methacrylic acid and ethylene dimethacrylate onto homemade near-monodispersed chloromethylated polydivinylbenzene beads. The chromatographic behaviour of a column packed with these imprinted beads was compared with another column packed with irregular particles obtained by grinding a bulk pyrimethanil-imprinted polymer (P2). The comparison was made using the kinetic model of non-linear chromatography, studying the elution of the template and of two related substances, cyprodinil and mepanipyrim. Extension of the region of linearity, capacity factors for the template and the related substances, column selectivity, binding site heterogeneity, apparent affinity constant (K) and lumped kinetic association (k_a) and dissociation rate constant (k_d) were studied during a large interval of solute concentration, ranging between 1 and 2000 μg/ml. From the experimental results obtained, in the linearity region of solute concentration column selectivity and binding site heterogeneity remained essentially the same for the two columns, while column capacity (at 20 μg/ml, P1 = 23.1, P2 = 11.5), K (at 20 μg/ml, P1 = 8.3 × 10⁶ M⁻¹, P2 = 2.5 × 10⁶ M⁻¹) and k_a (at 20 μg/ml, P1 = 3.5 μM⁻¹ s⁻¹, P2 = 0.47 μM⁻¹ s⁻¹) significantly increased and k_d (at 20 μg/ml, P1 = 0.42 s⁻¹, P2 = 0.67 s⁻¹) decreased for the column packed with the imprinted beads. These results are consistent with an influence of the polymerisation method on the morphology of the resulting polymer and not on the molecular recognition properties due to the molecular imprinting process.     

Al(III)-selective electrode based on newly synthesized xanthone derivative as neutral ionophore

The suitability of a xanthone derivative, 1-hydroxy-3-methyl-9H-xanthen-9-one (HMX) as a neutral ionophore for the preparation of a polyvinylchloride (PVC) membrane electrode for aluminum(III) ions was investigated. The prepared electrode exhibits a Nernstian response for Al³⁺ ions over a wide concentration range (1.0 × 10⁻⁶ to 1.6 × 10⁻¹ M) with a limit of detection 6.0 × 10⁻⁷ M. It has a relatively fast response time and can be used for at least three months without any considerable divergence in potentials. The proposed membrane electrode revealed very good selectivity for Al³⁺ ions over a wide variety of other cations and could be used at a working pH range of 3.0-8.5. It was used as an indicator electrode in potentiometric titration of aluminum ions with EDTA and in the determination of Al³⁺ in different real samples.     

Biomimetic sensor based on MnMn complex as manganese peroxidase mimetic for determination of rutin

A novel biomimetic sensor for rutin determination based on a dinuclear complex [Mn^IIIMn^II(Ldtb)(μ-OAc)₂]BPh₄ containing an unsymmetrical dinucleating ligand, 2-[N,N-bis(2-pyridylmethyl)-aminomethyl]-6-[N-(3,5-di-tert-butyl-2-oxidoben-zyl)-N-(2-pyridylamino)aminomethyl]-4-methylphenol (H₂Ldtb), as a manganese peroxidase mimetic was developed. Several parameters were investigated to evaluate the performance of the biomimetic sensor obtained after the incorporation of the dinuclear complex in a carbon paste. The best performance was obtained in 75:15:10% (w/w/w) of the graphite powder:Nujol:Mn^IIIMn^II complex, 0.1 mol L⁻¹ phosphate buffer solution (pH 6.0) and 4.0 × 10⁻⁵ mol L⁻¹ hydrogen peroxide. The response of the sensor towards rutin concentration was linear using square wave voltammetry in the range of 9.99 × 10⁻⁷ to 6.54 × 10⁻⁵ mol L⁻¹ (r = 0.9998) with a detection limit of 1.75 × 10⁻⁷ mol L⁻¹. The recovery study performed with pharmaceuticals ranged from 96.6% to 103.2% and the relative standard deviation was 1.85% for a solution containing 1.0 × 10⁻³ mol L⁻¹ rutin (n = 6). The lifetime of this biomimetic sensor was 200 days (at least 750 determinations). The results obtained for rutin in pharmaceuticals using the biomimetic sensor and those obtained with the official method are in agreement at the 95% confidence level.