Solid-phase ultraviolet absorbance spectrophotometric multisensor for the simultaneous determination of butylated hydroxytoluene and co-existing antioxidants

Continuous flow injection and UV spectrophotometric detection have been proposed for simultaneous determination of the two binary mixtures, butylated hydroxytoluene (BHT)/n-propyl gallate (n-PG) and butylated hydroxytoluene (BHT)/butylated hydroxyanisole (BHA), in food and cosmetics samples. The method is based on the different residence times of each antioxidant when the flow cell is packed to a height of 25 mm with silica C₁₈ using methanol-water 50:50% (v/v) as a carrier with a flow rate of 1.25 and 1.10 ml min⁻¹, respectively. The determination of each antioxidant is based on the measurement of its absorbance at its maximum wavelengths using a DAD detector at 30 and 180 s for the mixture n-PG-BHT and 90 and 220 s for BHA-BHT. Calibration graphs were linear over the range 10.0-300.0 μg ml⁻¹ for each antioxidant in both mixtures. The relative standard deviations were 2.5% for BHT and 2.0% for the co-existing antioxidant. Resolution of the n-PG-BHT mixture in ratios between 1:8 and 8:1 and the BHA-BHT mixture in ratios between 1:10 and 10:1 is possible. The method was applied to the determination of both antioxidants in fat foods and cosmetics samples with recoveries ranging between 101 and 105%.     

Glassy carbon electrodes modified with gold nanoparticles for the simultaneous determination of three food antioxidants

Electrochemical behavior of three antioxidants: butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and butylated hydroquinone (TBHQ), was investigated at a glassy carbon electrode modified with gold nanoparticles (AuNPs/GCE). This electrode was characterized by scanning electron microscopy (SEM). The experimental results indicated that the modified electrode was strongly electroactive during the redox reactions of BHA, BHT and TBHQ, and this was confirmed by the observed increased redox peak currents and shifted potentials; in addition, the oxidation products of BHA and TBHQ were found to be the same. The experimental conditions were optimized and the oxidation peaks of BHA and BHT were clearly separated. Based on this, an electrochemical method was researched and developed for the simultaneous determination of BHA, BHT and TBHQ in mixtures with the use of first derivative voltammetry; the linear concentration ranges were 0.10–1.50 μg mL⁻¹, 0.20–2.20 μg mL⁻¹ and 0.20–2.80 μg mL⁻¹, and detection limits were 0.039, 0.080 and 0.079 μg mL⁻¹, for BHA, BHT and TBHQ, respectively. The proposed method was successfully applied for the analysis of the three analytes in edible oil samples.     

Simultaneous determination of N-acetyl-p-aminophenol and p-aminophenol with poly(3,4-ethylenedioxythiophene) modified glassy carbon electrode

A sensitive and selective method was developed for the determination of N-acetyl-p-aminophenol (APAP) and p-aminophenol (PAP) using poly(3,4-ethylenedioxythiophene) (PEDOT)-modified glassy carbon electrode (GCE). Cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical reaction of APAP and PAP at the modified electrode. Both APAP and PAP showed quasireversible redox reactions with formal potentials of 367 mV and 101 mV (vs. Ag/AgCl), respectively, in phosphate buffer solution of pH 7.0. The significant peak potential difference (266 mV) between APAP and PAP enabled the simultaneous determination both species based on differential pulse voltammetry. The voltammetric responses gave linear ranges of 1.0 × 10⁻⁶-1.0 × 10⁻⁴ mol L⁻¹ and 4.0 × 10⁻⁶-3.2 × 10⁻⁴ mol L⁻¹, with detection limits of 4.0 × 10⁻⁷ mol L⁻¹ and 1.2 × 10⁻⁶ mol L⁻¹ for APAP and PAP, respectively. The method was successfully applied for the determination of APAP and PAP in pharmaceutical formulations and biological samples.     

Simultaneous voltammetric determination of paracetamol and caffeine in pharmaceutical formulations using a boron-doped diamond electrode

A simple and highly selective electrochemical method was developed for the single or simultaneous determination of paracetamol (N-acetyl-p-aminophenol, acetaminophen) and caffeine (3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione) in aqueous media (acetate buffer, pH 4.5) on a boron-doped diamond (BDD) electrode using square wave voltammetry (SWV) or differential pulse voltammetry (DPV). Using DPV with the cathodically pre-treated BDD electrode, a separation of about 550 mV between the peak oxidation potentials of paracetamol and caffeine present in binary mixtures was obtained. The calibration curves for the simultaneous determination of paracetamol and caffeine showed an excellent linear response, ranging from 5.0 × 10⁻⁷ mol L⁻¹ to 8.3 × 10⁻⁵ mol L⁻¹ for both compounds. The detection limits for the simultaneous determination of paracetamol and caffeine were 4.9 × 10⁻⁷ mol L⁻¹ and 3.5 × 10⁻⁸ mol L⁻¹, respectively. The proposed method was successfully applied in the simultaneous determination of paracetamol and caffeine in several pharmaceutical formulations (tablets), with results similar to those obtained using a high-performance liquid chromatography method (at 95% confidence level).     

Determination of adrenaline by using inhibited Ru(bpy)3 electrochemiluminescence

Adrenaline was found to inhibit strongly the electrochemiluminescence (ECL) from the Ru(bpy)₃²⁺/tripropylamine system when a working Pt electrode was maintained at 1.05 V (versus Ag/AgCl) in pH 8.0 phosphate buffer. On this basis, a flow injection (FI) procedure with inhibited electrochemiluminescence detection has been developed for determination of adrenaline. The method exhibited a good reproducibility, sensitivity, and stability with a detection limit (signal-to-noise ratio = 3) of 7.0×10⁻⁹ mol l⁻¹ and dynamic concentration range of 2×10⁻⁸ to 1×10⁻⁴ mol l⁻¹. The relative standard deviation was 2.2% for 1.0×10⁻⁶ mol l⁻¹ adrenaline (n=11). The method was successfully applied to the determination of adrenaline in pharmaceutical samples. Moreover, ECL emission spectra, UV-Vis absorption spectra and cyclic voltammograms of Ru(bpy)₃²⁺/tripropylamine/adrenaline were studied. The inhibition mechanism has been proposed as the interaction of electrogenerated Ru(bpy)₃^2+* and the o-benzoquinone derivatives, adrenochrome and adrenalinequinone, at the electrode surface.     

High selective SiO2-Al2O3 mixed-oxide modified carbon paste electrode for anodic stripping voltammetric determination of Pb(II)

The main purpose of this study is to develop an inexpensive, simple, selective and especially highly selective modified mixed-oxide carbon paste electrode (CPE) for voltammetric determination of Pb(II). For the preliminary screening purpose, the catalyst was prepared by modification of SiO₂-Al₂O₃ mixed-oxide and characterized by TG, CHN elemental analysis and FTIR spectroscopy. Using cyclic voltammetry the electroanalytical characteristics of the catalyst have been determined, and consequently the modified mixed-oxide carbon paste electrode was constructed and applied for determination of Pb(II). The electroanalytical procedure for determination of the Pb(II) comprises two steps: the chemical accumulation of the analyte under open-circuit conditions followed by the electrochemical detection of the preconcentrated species using differential pulse anodic stripping voltammetry. During the preconcentration step, Pb(II) was accumulated on the surface of the modifier by the formation of a complex with the nitrogen atoms of the pyridyl groups in the modifier. The peak currents increases linearly with Pb(II) concentration over the range of 2.0 × 10⁻⁹ to 5.2 × 10⁻⁵ mol L⁻¹ (r² = 0.9995).The detection limit (three times signal-to-noise) was found to be 1.07 × 10⁻⁹ mol L⁻¹ Pb(II). The chemical and instrumental parameters have been optimized and the effect of the interferences has been determined. The Proposed method was used for determination of lead ion in the real samples.     

Electrochemiluminescence from Ru(bpy)3 immobilized in poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)-poly(vinyl alcohol) composite films

Electrochemical behavior and electrogenerated chemiluminescence (ECL) of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) immobilized in poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)-poly(vinyl alcohol) (PEDOT/PSS-PVA) composite films via ion-exchange have been investigated with tripropylamine (TPA) as the co-reactant at a glassy carbon electrode. The immobilized Ru(bpy)₃²⁺ performed a surface-controlled electrode reaction. The Ru(bpy)₃²⁺ modified electrode showed a fast ECL response to TPA, and was used for the ECL detection of TPA with high sensitivity. The ECL intensity was linearly related to concentrations of TPA over the range from 0.50 μmol L⁻¹ to 0.80 mmol L⁻¹, and the detection limit was 0.10 μmol L⁻¹ (S/N = 3). The as-prepared electrode exhibited good precision and long-term stability for TPA determination.     

Novel platinum(II) selective membrane electrode based on 1,3-bis(2-cyanobenzene)triazene

A plasticized poly (vinyl chloride) membrane electrode based on 1,3-bis(2-cyanobenzene)triazene (CBT) for highly selective determination of platinum(II) (in PtCl₄²⁻ form) is developed. The electrode showed a good Nernstian response (29.8 ± 0.3 mV decade⁻¹) over a wide concentration range (1.0 × 10⁻⁶ to 1.0 × 10⁻² mol L⁻¹). The limit of detection was 5.0 × 10⁻⁷ mol L⁻¹. The electrode has a response time of about 40 s, and it can be used for at least 1 month without observing any considerable deviation from Nernstian response. The proposed electrode revealed an excellent selectivity toward platinum(II) ion over a wide variety of alkali, alkaline earth, transition, and heavy metal ions, and it could be used in the pH range of 3.2-5.1. The practical utility of the electrode has been demonstrated by its use in determination of platinum ion in, alloy, tap, mineral and river water samples.     

Self-assembled monolayer of nickel(II) complex and thiol on gold electrode for the determination of catechin

Self-assembled monolayers of a nickel(II) complex and 3-mercaptopropionic acid on a gold electrode were obtained for determination of catechin by square wave voltammetry. The complex [Ni^IIL] with L = [N-(methyl)-N′-(2-pyridylmethyl)-N,N′-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-1,3-propanediamine[nickel(II)] was synthesized and characterized by ¹H NMR, IR, and electronic spectroscopies and electrochemical methods. The optimized conditions obtained for the electrodes were 0.1 mol L⁻¹ phosphate buffer solution (pH 7.0), frequency of 80.0 Hz, pulse amplitude of 60.0 mV and scan increment of 10.0 mV. Under these optimum conditions, the resultant peak current on square wave voltammograms increases linearly with the concentration of catechin in the range of 3.31 × 10⁻⁶ to 2.53 × 10⁻⁵ mol L⁻¹ with detection limits of 8.26 × 10⁻⁷ mol L⁻¹. The relative standard deviation for a solution containing 1.61 × 10⁻⁵ mol L⁻¹ catechin solution was 2.45% for eight successive assays. The lifetime of the Ni(II) complex-SAM-Au electrode was investigated through testing every day over 4 weeks. The results showed apparent loss of activity after 20 days. The results obtained for catechin in green tea samples using the proposed sensor and those obtained by electrophoresis are in agreement at the 95% confidence level.     

Zirconium ion selective electrode based on bis(diphenylphosphino) ferrocene incorporated in a poly(vinyl chloride) matrix

A novel potentiometric zirconium - PVC matrix membrane sensor incorporating bis(diphenylphosphino) ferrocene as an electroactive material and tris(2-ethylhexyl)phosphate as solvent mediator is described. In mixed acetate buffer solution of pH 4.8, the sensor displays a rapid and linear response for zirconium ion over the concentration range 1.0 × 10⁻¹ to 1.0 × 10⁻⁷ mol L⁻¹ with a good slope of 59.7 ± 0.3 mV per decade and detection limit 1.8 × 10⁻⁸ mol L⁻¹. The best performance was obtained with membrane composition 33% PVC, 65% TEHP, 1% NaTPB and 1% ionophore. The proposed electrode revealed excellent selectivity for zirconium ion over a wide variety of alkali, alkaline earth, transition and heavy metal ions and could be used in a pH range of 4.15-7.8. The electrode was applied for at least 1 month without any considerable divergence in the potential responses. The practical utility of the electrode has been demonstrated by its use as an indicator electrode in the potentiometric titration of zirconium ions with sodium fluoride and in determination of zirconium ion in some alloy, tape and waste water 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.     

Fast and direct determination of butylated hydroxyanisole in biodiesel by batch injection analysis with amperometric detection

We report here, for the first time, application of batch injection analysis (BIA) with amperometric detection for determination of the phenolic antioxidant butylated hydroxyanisole (BHA) in biodiesel. A sample plug was directly injected onto a boron-doped diamond electrode immersed in 50% v/v hydroethanolic solution with 0.1 mol L⁻¹ HClO₄ using an electronic micropipette. Importantly, the only preparation step required for biodiesel analysis is dilution in the same hydroethanolic electrolyte solution. Our proposed method has several advantages for routine biodiesel analysis, including: a low relative standard deviation between injections (0.29%, n = 20), high analytical frequency (120 h⁻¹), adequate recovery values (93-101%) for spiked samples, satisfactory accuracy (based on comparative determinations by high-performance liquid-chromatography), and a low detection limit (100 ng of BHA per g of biodiesel). Finally, our method can be adapted for the determination of other antioxidants in biodiesel samples.     

Preliminary evaluation of monolithic column high-performance liquid chromatography with tris(2,2′-bipyridyl)ruthenium(II) chemiluminescence detection for the determination of quetiapine in human body fluids

High-performance liquid chromatography (HPLC) with tris(2,2′-bipyridyl)ruthenium(II) chemiluminescence detection methodology is reported for the determination of the atypical antipsychotic drug quetiapine and the observation of its major active and inactive metabolites in human urine and serum. The method uses a monolithic chromatographic column allowing high flow rates of 3 mL min⁻¹ enabling rapid quantification. Flow injection analysis (FIA) with tris(2,2′-bipyridyl)ruthenium(II) chemiluminescence detection and HPLC time of flight mass spectrometry (TOF-MS) were used for the determination of quetiapine in a pharmaceutical preparation to establish its suitability as a calibration standard. The limit of detection achieved with FIA was 2 × 10⁻¹¹ mol L⁻¹ in simple aqueous solution. The limits of detection achieved with HPLC were 7 × 10⁻⁸ and 2 × 10⁻¹⁰ mol L⁻¹ in urine and serum, respectively. The calibration range for FIA was between 5 × 10⁻⁹ and 1 × 10⁻⁶ mol L⁻¹. The calibration ranges for HPLC were between 1 × 10⁻⁷-1 × 10⁻⁴ and 1 × 10⁻⁸-1 × 10⁻⁴ mol L⁻¹ in urine and serum, respectively. The quetiapine concentrations in patient samples were found to be 3 × 10⁻⁶ mol L⁻¹ in urine and 7 × 10⁻⁷ mol L⁻¹ in serum. Without the need for preconcentration, the HPLC detection limits compared favourably with those in previously published methodologies. The metabolites were identified using HPLC-TOF-MS.     

Voltammetric determination of pyridoxine (Vitamin B6) at a carbon paste electrode modified with vanadyl(IV)-Salen complex

The preparation and electrochemical characterization of a carbon paste electrode modified with the N,N-ethylene-bis(salicylideneiminato)oxovanadium(IV) complex [VO(Salen)] as well as its behavior in relation to the oxidation of pyridoxine (Vitamin B₆) are described. The electrochemical behavior of the modified electrode and the electrooxidation of pyridoxine were investigated using cyclic voltammetry. The best voltammetric response was obtained for an electrode composition of 15% (m/m) [VO(Salen)] in the paste, KCl solution of pH 5.5-8.0 and scan rate of 25 mV s⁻¹. A sensitive linear voltammetric response for pyridoxine was obtained in the concentration range of 4.5×10⁻⁴ to 3.3×10⁻³ mol l⁻¹ with a slope of 42.5 μA mmol⁻¹ l, and a detection limit (3σ/slope) of 3.7×10⁻⁵ mol l⁻¹ using linear sweep voltammetry. Among several compounds tested only Vitamin B₁ seems to interfere in the analyte signal. The concentrations of pyridoxine in pharmaceutical formulations using the proposed electrode and an official spectrophotometric method based in the reaction with N,N-diethyl-p-phenylenediamine are in agreement at the 95% confidence level and within an acceptable range of error.     

Simultaneous determination of antioxidants at a chemically modified electrode with vitamin B12 by capillary zone electrophoresis coupled with amperometric detection

In the paper, a new kind of vitamin B₁₂ (acquo-cobalamine) chemically modified electrode was fabricated and applied in capillary zone electrophoresis coupled with amperometric detection (CZE-AD) for simultaneous determination of six antioxidants in fruits and vegetables. The catalytic electrochemical properties of the chemically modified electrode could obviously enhance oxidation peak heights responses by about five times to glutathione, ascorbic acid, vanillic acid, chlorogenic acid, salicylic acid, and caffeic acid compared with common carbon disk electrode. Furthermore, the effects of working electrode potential, pH and concentration of running buffer, separation voltage and injection time on CZE-AD were investigated. Under the optimum conditions, the six analytes could be completely separated and detected in a borate-phosphate buffer (pH 8.4) within 15 min. Their linear ranges were from 2.5 × 10⁻⁷ to 1.0 × 10⁻⁴ mol L⁻¹ and the detection limits were as low as 10⁻⁸ mol L⁻¹ magnitude (S/N = 3). The proposed method has been successfully employed to monitor the six analytes in practical samples with recoveries in the range 96.0-106.0% and RSDs less than 5.0%. Above results demonstrate that capillary zone electrophoresis coupled with electrochemical detection using vitamin B₁₂ modified electrode as detector is of convenient preparation, high sensitivity, good repeatability, and could be used in the rapid determination of practical samples.     

A new ytterbium(III) PVC membrane electrode based on 6-methy-4-{[1-(1H-pyrrol-2-yl)methylidene]amino}-3-thioxo-3,4dihydro-1,2,4-triazin-5(2H)-one

This study presents the development of an original electrode, employing 6-methy-4-{[1-(1H-pyrrol-2-yl)methylidene]amino}-3-thioxo-3,4dihydro-1,2,4-triazin-5(2H)-one (PMTO) as a suitable ionophore. Interestingly, the electrode performance provided a very good response for Yb³⁺ in a wide concentration range (from 1.0 × 10⁻⁶ to 1.0 × 10⁻¹ mol L⁻¹) with a detection limit of 4.6 × 10⁻⁷ mol L⁻¹ and a slope of 19.5 ± 0.3 mV per decade of Yb³⁺ concentration. Furthermore, it possessed a fast response time of about 10 s and it functioned in the pH range of 3.3-8.0 with a usage of at least 2 months without observing any deviations. Noticeably, the proposed electrode revealed an excellent selectivity for Yb³⁺ over a broad variety of alkali, alkaline earth, transition and heavy metal ions. The practical applicability of the electrode was demonstrated by its utilization as an indicator electrode in the potentiometric titration of Yb³⁺ ions with EDTA and in the determination of F⁻ in mouth wash samples. Additionally, it was also applied for the determination of Yb³⁺ ions in binary mixtures.     

Electrochemical determination of iodide on a vanadium oxide-polypropylene carbonate coated glassy carbon electrode

A vanadium oxide-modified glassy carbon electrode was simply and conveniently fabricated by casting vanadium tri(isoproxide) oxide (VO(OC₃H₇)₃) and poly(propylene carbonate) (PPC) onto the glassy carbon electrode surface. The electrochemical properties of iodide at the VO(OC₃H₇)₃-PPC film-modified glassy carbon electrode were investigated by cyclic voltammetry, and an anodic peak was observed at approximately +0.71 V (vs. SCE). Based on this, a sensitive and convenient electrochemical method was proposed for the determination of iodide. Flow injection amperometry (FIA) exhibited a good linear relationship with the concentration of iodide in the range of 5 × 10⁻⁷ mol L⁻¹ and 1 × 10⁻³ mol L⁻¹, and the detection limit was 1 × 10⁻⁷ mol L⁻¹. Quantitative recovery of iodide in synthetic samples has been obtained and the interferences from different cations and anions have been studied. The method has been successfully applied to the determination of iodide in dry edible seaweed. The concentrations of iodide measured by this method are in good agreement with those obtained by spectrophotometric method.     

Tris(2,2'-bipyridyl)ruthenium(II)-Zirconia-Nafion composite modified electrode applied as solid-state electrochemiluminescence detector on electrophoretic microchip for detection of pharmaceuticals of tramadol, lidocaine and ofloxacin

Tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺)-Zirconia-Nafion composite modified glassy carbon disk electrode as a solid-state electrochemiluminescence (ECL) detector is successfully applied to an electrophoretic microchip system with a wall-jet configuration. Pharmaceuticals such as tramadol, lidocaine and ofloxacin were selected to characterize the performance of this microchip capillary electrophoresis (CE)-ECL detection system. Voltammetric and ECL behaviors of immobilized Ru(bpy)₃²⁺ were investigated in lidocaine system. Influences of the separation electric field to cyclic voltammograms (CVs) of the immobilized Ru(bpy)₃²⁺ were also investigated. Tramadol, lidocaine and ofloxacin can be baseline separated without any additives. The detection limits (S/N = 3) were 2.5 × 10⁻⁵ mol L⁻¹ for tramadol, 5.0 × 10⁻⁶ mol L⁻¹ for lidocaine, 1.0 × 10⁻⁵ mol L⁻¹ for ofloxacin under the sample injection of picoliters, and the linear ranges were from 5.0 × 10⁻⁵ to 2.5 × 10⁻³ mol L⁻¹ for tramadol, 1.0 × 10⁻⁵ to 1.0 × 10⁻³ mol L⁻¹ for lidocaine, and 1.0 × 10⁻⁵ to 2.5 × 10⁻³ mol L⁻¹ for ofloxacin, respectively.     

Electrochemiluminescent behaviors of alkaloids and tris(2,2'-bipyridine) ruthenium in organically modified silicate film

Electrogenerated chemiluminescences (ECLs) of alkaloids, such as berberine, trigonelline, allantoin and betaine, were studied in an aqueous alkaline buffer solution (pH 9.5), based on tris(2,2′-bipyridine)ruthenium(II) [Ru(bpy)₃²⁺] immobilized in organically modified silicates (ORMOSILs) film on a glassy carbon electrode (GCE). The immobilized Ru(bpy)₃²⁺ showed good electrochemical and photochemical activities. In a flow system, the eluted alkaloids were oxidized on the modified GCE, and reacted with immobilized Ru(bpy)₃²⁺ at the potential of +1.50 V (versus Ag/AgCl). The luminescence with λ_max 610 nm was caused by a reaction of electrolytically formed Ru(bpy)₃³⁺ with an oxidized amine group to generate Ru(bpy)₃^2+*. The determination limit was 5 × 10⁻⁶ mol L⁻¹, 8 × 10⁻⁶ mol L⁻¹, 2.0 × 10⁻⁵ mol L⁻¹ and 5.0 × 10⁻⁵ mol L⁻¹ for berberine, trigonelline, allantoin and betaine at S/N 3, respectively. In addition, the factors affecting the determination of the four alkaloids were also studied.     

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.