Dihexadecyl Hydrogen Phosphate Research Articles

Development of Electrochemical Platform Based on Molecularly Imprinted Poly(methacrylic acid) Grafted on Iniferter‐modified Carbon Nanotubes for 17β‐Estradiol Determination in Water Samples

AbstractThis paper describes the development of a new electrochemical sensor for 17β‐estradiol (E2) determination based on glassy carbon electrode (GCE) modified with molecularly imprinted polymer grafted onto iniferter‐multiwall carbon nanotubes surface (MIP‐MWCNT) and dihexadecyl‐hydrogen‐phosphate (DHP). The electrochemical method was based on closed‐circuit preconcentration of E2 in 0.1 mol L−1 phosphate buffer (pH 7.0) during 500 s. Upon preconcentration, E2 was determined by differential pulse voltammetry (DPV) exhibiting a limit of detection of 0.01 μmol L−1. The sensor exhibited higher selectivity toward E2 and it was applied for E2 determination in natural water samples, with accuracy attested by HPLC‐DAD.

Chemically modified electrode based on dihexadecyl hydrogen phosphate and carbonaceous materials: improvement of analytical and electrochemical features applied to uranium determination

This work deals about the evaluation and improvement of analytical and electrochemical features of chemically modified electrode based on dihexadecyl hydrogen phosphate (DPH) and carbonaceous materials. The electrochemical features of films obtained were evaluated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Between the modifications evaluated, the glassy carbon electrode (GCE) modified with CB and DPH (DHP-CB/GCE) showed lower resistance to charge transfer and higher electron transfer rate. Additionally, the highest current of U(VI) was obtained with DHP-CB/GCE in a very stable way, the process present quasi-reversible behavior and it is controlled by a mixture of diffusion and absorption. The best instrumental conditions for U(VI) determination were obtained applying frequency of 15 Hz, amplitude of 100 mV, and deposition potential of − 0.1 V (by square wave cathodic stripping voltammetry). Among the electrolyte compositions (acetate and citrate buffers), ionic strength (from 0.10, 0.15, to 0.20 mol L−1), and pH (from 3.6 to 5.6) evaluated, the highest current of U(VI) were obtained in 0.15 mol L−1 of acetate buffer, pH 5.6. The method was accurate, linear, and sensitive (detection limit of 0.088 μg L−1 using 300 s of deposition).

Electroanalytical determination of eugenol in clove oil by voltammetry of immobilized microdroplets

The determination of eugenol employing voltammetry of immobilized microdroplets (VIM) is reported in this work. The construction of the electrode was based on a glassy carbon substrate modified with carbon black nanoparticles and eugenol standard or clove oil sample within a dihexadecyl hydrogen phosphate (DHP) film. The different experimental parameters related to this proposed procedure, i.e., supporting electrolyte composition, pH, ionic strength, and square-wave voltammetry (SWV) parameters (amplitude, frequency, and step potential) were optimized. By doing that, the SWV measurements were performed on the following optimum experimental conditions: 0.2 mol L−1 phosphate buffer solution (pH 2.0), amplitude 90 mV, frequency 30 Hz, and step potential 5 mV. The analytical curve for eugenol was linear in the wide range from 0.03 to 26 μg (r = 0.999) with limits of detection (LOD) and quantification (LOQ) of 0.13 and 0.42 ng, respectively. Three commercial clove oil samples were successfully immobilized and analyzed using the proposed VIM procedure showing eugenol concentrations ranging from 14.0 to 68.3%. Comparing the results obtained by the proposed and comparative procedure (spectrophotometric), relative standard deviations (RSDs) lower than 5.0% were verified, demonstrating the concordance of the results obtained by both methods.

Square-wave adsorptive stripping voltammetric determination of nanomolar levels of bezafibrate using a glassy carbon electrode modified with multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film

A highly sensitive method for bezafibrate determination using a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film based on square-wave adsorptive stripping voltammetry (SWAdSV) is proposed. The electrochemical behaviour of bezafibrate has been studied by cyclic voltammetry, showing an irreversible anodic peak at a potential of 1.09 V in 0.1 mol L(-1) phosphate buffer solution (pH 2.0). A study of the scan rate showed that the oxidation of bezafibrate is an adsorptive-controlled process, involving the transfer of two electrons and two protons per molecule. The analytical curve was linear over a bezafibrate concentration range from 50 to 910 nmol L(-1), with a detection limit of 16 nmol L(-1). This analytical method was successfully applied for benzafibrate determination in pharmaceutical formulations, with results showing good agreement with those obtained using a comparative spectrophotometric method, and has the potential for field application.

Modification of well-aligned carbon nanotubes with dihexadecyl hydrogen phosphate: application to highly sensitive nanomolar detection of simvastatin

The first usage of dihexadecyl hydrogen phosphate (DHP)-modified highly oriented multi-walled carbon nanotube (MWCNTs) forests in a sensor configuration was developed to investigate the electrochemical oxidation and determination of simvastatin (SV) in pharmaceutical dosage forms. Synthesis of well-aligned MWCNTs on a conductive Ta substrate by catalytic vapor deposition technique using a common chemical, ethylenediamine, and without being plasma-aided was reported. The electrochemical behavior and oxidation of SV at the aligned MWCNTs/DHP/Ta electrode were discussed in detail through cyclic voltammetry and differential pulse voltammetry. This modified electrode showed considerably higher electrocatalytic activity for SV than bare Ta electrode or entangled MWCNTs powder electrode, due to presence of the alignment and mutual separation of CNTs. Under the optimal conditions, the A-MWCNTs/DHP/Ta-modified electrode showed a wide linear range from 0.01 to 1 μM with a detection limit of 0.01 nM demonstrating promising results for the future usage in clinical applications.

Square-wave voltammetric determination of paraquat using a glassy carbon electrode modified with multiwalled carbon nanotubes within a dihexadecylhydrogenphosphate (DHP) film

A simple, highly sensitive square-wave voltammetric method is reported for the sensing of paraquat (PQ) in natural water samples. A glassy carbon electrode modified with functionalized multiwalled carbon nanotubes (MWCNTs) immobilized within a Dihexadecylhydrogenphosphate (DHP) film was prepared and characterized with cyclic, differential-pulse and square-wave voltammetry. The modified electrode was found to exhibit a remarkably enhanced electro-activity toward the sensing of paraquat. Under optimum experimental conditions, using square wave voltammetry, the sensing of paraquat is achievable over the concentration range from 5.0×10−8 to 1.5×10−6molL−1 with a detection limit (3σ) of 1.0×10−8molL−1. The protocol is explored toward potential interferents and is applied for the analysis of paraquat in natural waters with the results agreeing with independently verified HPLC at a 95% confidence level.

Enhanced oxidation and detection of methyl parathion using an acetylene black nanoparticle–dihexadecyl hydrogen phosphate composite film

Download options Please wait... Article information DOI https://doi.org/10.1039/C3AY41574K Article type Paper Submitted 11 Sep 2013 Accepted 18 Sep 2013 First published 19 Sep 2013 Download Citation Anal. Methods, 2013,5, 6637-6641 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Enhanced oxidation and detection of methyl parathion using an acetylene black nanoparticle–dihexadecyl hydrogen phosphate composite film Z. Shi, J. Wang, S. Zhang and X. Tan, Anal. Methods, 2013, 5, 6637 DOI: 10.1039/C3AY41574K To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Zhen Shi Jinshou Wang Shenghui Zhang Xiaohong Tan

Determination of gemfibrozil in pharmaceutical and urine samples by square-wave adsorptive stripping voltammetry using a glassy carbon electrode modified with multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film

Glassy carbon electrode modified with functionalized multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film was used to develop a sensitive and simple square-wave adsorptive stripping voltammetric (SWAdSV) method for the determination of gemfibrozil. The cyclic voltammograms obtained showed one irreversible anodic peak for gemfibrozil at a potential of 1.3V using a 0.1molL−1 phosphate buffer solution (pH2.0). The cyclic voltammetric responses were studied with regard to scan rate, and the number of electrons transferred during the oxidation process was calculated. A calibration curve for gemfibrozil in the concentration range from 75 to 1000nmolL−1 with a detection limit of 53nmolL−1 were obtained. The proposed SWAdSV method was successfully applied to determine gemfibrozil in pharmaceutical and urine samples with good accuracy and precision.

Electrochemical determination of chrysophanol based on the enhancement effect of acetylene black nanoparticles

Acetylene black (AB) nanoparticles were readily dispersed into water in the presence of dihexadecyl hydrogen phosphate. After evaporation of water, the surface of glassy carbon electrode (GCE) was coated with AB nanoparticles as confirmed from the scanning electron microscopy measurements. The transmission electron microscopy images indicated that AB nanoparticles possessed porous structure. Electrochemical behavior of chrysophanol was studied, and a sensitive oxidation peak was observed in pH 3.6 acetate buffer solution. Compared with the bare GCE, the AB nanoparticles-modified GCE greatly increased the oxidation peak current of chrysophanol, showing remarkable signal enhancement effect. The influences of pH value, amount of AB, accumulation potential and time on the signal enhancement of chrysophanol were studied. As a result, a novel electrochemical method was developed for the determination of chrysophanol. The linear range was from 1.5 to 200μgL−1, and the detection limit was 0.51μgL−1 (2.01×10−9M) after 2-min accumulation. Finally, this method was used in traditional Chinese medicines, and the results consisted with the values that obtained by high-performance liquid chromatography.

Enhanced oxidation and detection of toxic ractopamine using carbon nanotube film-modified electrode

Insoluble multi-walled carbon nanotube (MWCNT) was readily dispersed into water in the presence of dihexadecyl hydrogen phosphate, and then used to modify the surface of glassy carbon electrode (GCE) by means of solvent evaporation. Scanning electron microscopy test indicated that the GCE surface was coated with uniform MWCNT film. The resulting MWCNT film-modified GCE greatly enhanced the oxidation signal of ractopamine. The oxidation mechanism was studied, and it was found that the oxidation of ractopamine occurred at two phenolic hydroxyl groups, involving two protons and two electrons. Moreover, the influences of pH value, amount of MWCNT, accumulation potential and time were investigated on the oxidation signal of ractopamine. Based on the strong enhancement effect of MWCNT, a sensitive, rapid and simple electrochemical method was developed for the detection of ractopamine. The linear range was from 50μgL−1 to 2mgL−1, and the detection limit was 20μgL−1. Finally, this method was successfully used to detect the content of ractopamine in pork and liver samples, and the recovery was in the range from 93.1% to 107.2%.

Enhanced oxidation and detection of toxic clenbuterol on the surface of acetylene black nanoparticle-modified electrode

Acetylene black (AB) nanoparticles were easily dispersed into water in the presence of a special surfactant: dihexadecyl hydrogen phosphate (DHP). After that, the AB-DHP composite film was coated on the surface of glassy carbon electrode (GCE) after evaporating water. The resulting AB-DHP film exhibited remarkable enhancement to the oxidation of clenbuterol, and greatly increased the oxidation peak current of clenbuterol. The influences of pH value, amount of AB, accumulation potential and time were studied. As a result, a novel electrochemical method was developed for the detection of clenbuterol. The linear range is from 0.02 to 4mg L−1, and the detection limit is 10μg L−1. The method was successfully used to detect the concentration of clenbuterol in pork and liver samples. The recovery is in the range from 95.2% to 106.8%.

Preparation of parathion imprinted polymer beads and its applications in electrochemical sensing

Parathion imprinted polymer beads were prepared by free radical polymerization using parathion as template, methacrylic acid as functional monomer, divinyl benzene as cross-linking reagent and 2,2′-azobis(isobutyronitrile) as initiator. The obtained molecularly imprinted beads were characterized with transmission electron micrograph. The rebinding properties of these imprinted beads towards parathion were studied by saturation binding experiments using ultraviolet/visible spectroscopy. Effects of the template, functional monomer, cross-linking reagent and initiator on selective adsorption of parathion were investigated. The high selectivity of the imprinted beads was successfully demonstrated by their selective adsorption of free parathion from an ethanol–water (v/v = 1:5) solution. In addition, the parathion imprinted beads were dispersed into dihexadecyl hydrogen phosphate solution at the concentration of 1.0 mg mL −1. By coating this solution onto a glassy carbon electrode surface, a molecularly imprinted electrochemical sensor for parathion was obtained. The electrochemical sensor exhibited good selectivity and fast response to parathion. Under optimized experimental conditions, the peak currents were found linearly proportional to the parathion concentration in the range of 1.0 × 10 −7 mol L −1 to 1.0 × 10 −5 mol L −1 with a detection limit of 5.4 × 10 −8 mol L −1 (S/N = 3). The developed sensor was successfully employed for the determination of parathion in pear juice samples.

Trace determination of zirconium by adsorptive anodic stripping voltammetry of its complex with alizarin violet using a glassy carbon electrode modified with acetylene black-dihexadecyl hydrogen phosphate composite film

We report on a novel electrochemical method for the sensitive determination of trace zirconium (Zr) at a glassy carbon electrode modified with a film of acetylene black containing dihexadecyl hydrogen phosphate and in the presence of alizarin violet (AV). The method is based on the preconcentration of the Zr(IV)-AV complex at a potential of −200 mV (vs. SCE). The adsorbed complex is then oxidized, producing a response with a peak potential of 526 mV. Compared to the poor electrochemical signal at the unmodified GCE, the electrochemical response of Zr(IV)-AV complex is greatly improved, as confirmed by the significant increase in peak current. The effects of experimental conditions on the oxidation current were studied and a calibration plot established. The oxidation current is linearly related to the Zr(IV) concentration in the 8.0 pM to 10 nM concentration range (cAV = 0.2 μM) and 10 nM ~0.6 μM (cAV = 2.0 μM), and the detection limit (S/N = 3) is as low as 4.0 pM for a 3-min accumulation time. The method was successfully employed to the determination of zirconium in standard ore samples.

Sensing of nitric oxide using a glassy carbon electrode modified with an electrocatalytic film composed of dihexadecyl hydrogen phosphate, platinum nanoparticles, and acetylene black

Platinum nanoparticles were electrodeposited onto a film of dihexadecyl hydrogen phosphate deposited on a glassy carbon electrode (GCE) and modified with dispersed acetylene black. Scanning electron microscopy and electrochemical impedance spectroscopy revealed that this nanocomposite has a uniform nanostructure and a large surface area that enables fast electron-transfer kinetics. The modified GCE showed high electrocatalytic activity for the oxidation of nitric oxide (NO). Under optimal conditions, the oxidation peak current of nitric oxide is linearly related to the concentration of NO in the concentration range between 0.18 and 120 μM, and the detection limit is as low as 50 nM (at an S/N of 3). The modified electrode was successfully applied to sensing of NO as released from rat liver.

The amperometric determination of indole-3-acetic acid based on CeCl3-DHP film modified gold electrode

An amperometric sensor for the determination of indole-3-acetic acid (IAA) based on the CeCl3-DHP film modified gold electrode was developed. CeCl3 was dissolved into water in the presence of dihexadecyl hydrogen phosphate (DHP). The IAA sensor was prepared via evaporating solvent of the CeCl3-DHP dispersion on the gold electrode surface. The amperometric response of IAA on the CeCl3-DHP film modified gold electrode was investigated. The experimental results indicate that the passivation of the electrode due to the adsorption of the oxidation product of IAA decreases significantly at the CeCl3-DHP film modified gold electrode, in contrast to that at the bare and the DHP modified gold electrode. The experimental parameters were optimized and an electrochemical method for the determination of IAA was established. The oxidation peak current is linearly with the concentration of IAA from 1 × 10−7 to 2 × 10−5 mol l−1 and the detection limit is 3 × 10−8 mol l−1. The relative standard deviation of eight measurements is 3.2% for 5 × 10−7 mol l−1 IAA. The IAA in plant leaves were extracted and determined by the IAA sensor.

LC-ED with an Acetylene Black–Dihexadecyl Hydrogen Phosphate Composite Film-Modified Electrode for in Vivo Analysis of Thiols in Rat Striatal Microdialysate

Liquid chromatography with electrochemical detection (LC-ED), coupled with in vivo microdialysis sampling, has been used for analysis of thiols. An acetylene black–dihexadecyl hydrogen phosphate (AB–DHP) composite film-modified electrode was used as working electrode. The AB–DHP-modified electrode enabled efficient electrocatalytic oxidation of l-cysteine (l-Cys) and glutathione (GSH) with relatively high sensitivity, stability, and longevity. The peak currents of l-Cys and GSH were linear in the concentrations ranges 2.0 × 10−7–2.0 × 10−4 and 3.0 × 10−7–5.0 × 10−4 mol L−1, respectively, with calculated detection limits (S/N = 3) of 1.0 × 10−7 and 2.0 × 10−7 mol L−1, respectively. The method has been successfully used to measure the amounts of l-Cys and GSH in striatal microdialysate of freely moving rats.

Enhanced electrochemical detection of erythromycin based on acetylene black nanoparticles

Acetylene black nanoparticles (AB) were dispersed into water in the presence of dihexadecyl hydrogen phosphate (DHP), and used to modify the surface of glassy carbon electrode (GCE) via solvent evaporation. Due to the high sorption ability, large surface area and numerous active sites, the AB-modified GCE showed a strong enhancement effect on the oxidation of erythromycin, and greatly increased the peak current. The oxidation mechanism was investigated at the surface of AB-modified GCE, and two oxidation peaks were observed for erythromycin. The first oxidation peak is attributed to the removal of one electron from the nitrogen atom to form an aminium cation radical, and the second peak is due to the oxidation of the chemical product of aminium cation radical. The influence of pH value, amount of AB, accumulation potential and time was also studied, and a novel electrochemical method was developed for the determination of erythromycin. The linear range is from 2 × 10 −7 to 1 × 10 −5 M, and the limit of detection is 8 × 10 −8 M (58.72 μg L −1).

Electrochemical determination of xanthine and hypoxanthine in rat striatum with an acetylene black-dihexadecyl hydrogen phosphate composite film modified electrode by HPLC coupled with in vivo microdialysis

The fabrication and application of a new electrochemical detector for use in HPLC is presented. The detector consists of an electrode modified with a composite film composed of acetylene black and dihexadecyl hydrogen phosphate. The electrochemistry of xanthine and hypoxanthine at this chemically modified electrode (CME) was investigated by cyclic voltammetry. It is found that the CME exhibits efficient electrocatalytic activity towards xanthine and hypoxanthine, with good sensitivity, stability, and lifetime. The linear ranges cover three orders of magnitude, and the detection limits are 6.0 × 10−8 mol L−1 for xanthine and 2.5 × 10−7 mol L−1 for hypoxanthine (at an S/N ratio of 3). The method was coupled to in-vivo microdialysis sampling and successfully applied to quantify xanthine and hypoxanthine in rat striatal microdialysates of freely moving rats.

10.1007/s11175-008-2007-4

The electrochemical response of phenol at acetylene black (AB)-dihexadecyl hydrogen phosphate (DHP) composite modified glassy carbon electrode in the presence of cetyltrimethylammonium bromide (CTAB) was investigated. In this system, a sensitive oxidation peak at 0.62 V (SCE) was obtained. The electrode process and the influence of CTAB on the oxidation of phenol were explored by chronocoulometry and linear sweep voltammetry (LSV). Experimental conditions for the determination of phenol were optimized. In the range of 5.0 × 10−7 to 1.2 × 10−5 M, the phenol concentration was linear with the oxidation peak current and the detection limit was found to be 1.0 × 10−7 M for 3 min accumulation. The method was applied for the determination of phenol in lake water and the results were satisfactory.

Voltammetric determination of ethamsylate in bulk solution and pharmaceutical tablet by nano-material composite-film coated electrode

A sensitive electrochemical method was described for voltammetric determination of ethamsylate at a glassy carbon electrode (GCE) coated with a nano-material thin film. In this work, a nanometer material, namely, multi-wall carbon nanotubes (MWCNT) was dispersed successfully into water in the presence of dihexadecyl hydrogen phosphate (DHP) and a MWCNT–DHP composite film was conveniently obtained on the GCE surface. The electrochemical behavior of ethamsylate at this modified electrode was investigated and a pair of reversible redox peak was observed. Compared with the electrochemical response of ethamsylate at the bare GCE, the separation of peak potential (Δ E p) of ethamsylate decreased obviously from 438 to 40 mV and the current density of redox peaks increased greatly. Based on this, differential pulse voltammetry (DPV) was employed to determine ethamsylate. Various experimental parameters such as pH value of the supporting electrolyte, the amount of modifier and so on were optimized. Under optimal conditions, a linear response of ethamsylate was obtained in the range from 1.0 × 10 − 6 to 2.0 × 10 − 5 mol/L, and the detection limit was 6.0 × 10 − 7 mol/L. The proposed method was successfully applied to detect ethamsylate in pharmaceutical samples.