Britton-Robinson Research Articles

Determination of chloramphenicol by differential pulse voltammetry at carbon paste electrodes – The use of sodium sulfite for removal of oxygen from electrode surface

The possibility of determination of chloramphenicol by differential pulse voltammetry at four different carbon paste electrodes, in the full pH range (2–12) of Britton–Robinson (BR) buffer was investigated. Electrodes were prepared by mixing spectroscopic graphite powder or glassy carbon microbeads with mineral oil (Nujol) or tricresyl phosphate. Under optimal conditions (BR buffer pH 12, the electrode prepared from glassy carbon microbeads and tricresyl phosphate), linear calibration graph was obtained only in 10–5 M chloramphenicol concentration range. Determination of lower concentrations of chloramphenicol was complicated by irreproducible peak of oxygen from the carbon paste which overlapped with peak of chloramphenicol. Addition of sodium sulfite removed the oxygen peak without influence on the peak of chloramphenicol. Under optimal conditions (electrode paste made from glassy carbon microbeads, BR buffer pH 10 and 0.5 M sodium sulfite), straight calibration line was obtained in the 10–6 and 10–5 M chloramphenicol concentration range. Limit of determination was 5 × 10–7 mol/l.

Voltammetric Reduction Behavior and Electrode Kinetics

The electrochemical reduction behavior of cefepime and cefpirome has been studied using cyclic voltammetry in Britton Robinson (BR) buffer ranging from pH 2.0 to 12.0. Cefepime and cefpirome are found to give two well defined peaks and these peaks are attributed to the reduction of the azomethine group (>C=N-) by two electron process in two steps. Kinetic parameters such as diffusion coefficient (D) and forward rate constant (K o f,h) values are evaluated and a reduction mechanism is proposed. The result indicates that the process of both the compounds is irreversible and diffusion controlled. A simple and rapid differential pulse polarographic method has been developed for the determination of cefepime and cefpirome in pharmaceutical formulations and spiked urine samples using the standard addition method. The lower detection limits are found to be 4.6×10 -8 mol. L -1 and 8.52×10 -8 mol. L -1 for cefepime and cefpirome, respectively.

Adsorptive cathodic stripping voltammetric determination of curcumin in turmeric and human serum

A simple, rapid, reliable and fully validated differential pulse adsorptive cathodic stripping voltammetric procedure has been developed for determination of the curcumin in human serum and turmeric, based on its electrochemical reduction at a hanging mercury drop electrode. The Britton–Robinson (BR) buffer of pH 9.5 was found to be reasonable as a supporting electrolyte for the assay of the compound. The effect of different parameters, such as pH, accumulation potential and accumulation time, on the sensitivity of method was evaluated. Under the optimized conditions (accumulation potential –0.3 V, accumulation time 50 s, BR buffer pH 9.5), curcumin was generated one irreversible cathodic peak. This cathodic peak showed a linear dependence on the concentration of curcumin over the range of 5.0 × 10–9–2.8 × 10–7 mol l–1. The obtained detection limit under the optimal experimental conditions is 1.5 × 10–9 mol l–1 after 50 s of the accumulation time. The relative standard deviation of 1.12% for concentration of 5.0 × 10–8 mol l–1 with 50 s accumulation time was obtained. The procedure was used successfully to the assay of the curcumin in turmeric and spiked human serum, and a good agreement was obtained between the results of the proposed method and high performance liquid chromatography (HPLC) analysis.

Square-wave cathodic adsorptive stripping voltammetry of risperidone

Electrochemical properties and diffusion-adsorption behavior of risperidone (RPN), an antiphyscotic drug, on hanging mercury drop electrode (HMDE) were carried out in Britton–Robinson (BR) buffer. Some electrochemical parameters such as diffusion coefficient, number of transferred electrons and proton participated to its reduction mechanism and surface coverage coefficient were calculated from the results of cyclic voltammetry, square-wave voltammetry and constant potential electrolysis. RPN was found to be reduced with single two-electron/two-proton quasi-reversible mechanism controlled mainly by adsorption with some diffusion contribution at the potential about –1.58 V (vs Ag|AgCl electrode). Experimental parameters were optimized to develop a new, accurate, rapid, selective and simple square-wave cathodic adsorptive stripping voltammetric (SWCAdSV) method for direct determination of RPN in pharmaceutical dosage forms, spiked human urine and human serum samples without time-consuming steps prior to drug assay. This method was based on the relation between the peak current and the concentration of RPN and it was recognized that peak current of reduction wave linearly changes with the concentration of RPN in the concentration range of 1.5–150 nM, when optimum preconcentration potential –0.65 V and optimum preconcentration time 60 s were applied. In this method, limit of detection (LOD) was found as 5.18 nM (2.12 ppb). The method was successfully applied to determine the RPN content of commercial pharmaceutical preparations, spiked human serum and spiked human urine. The method was found to be highly accurate and precise, having a relative standard deviation of less than 4.80% for all applications.

A novel apigenin modified glassy carbon sensor electrode for the determination of copper ions in soil samples

In this study, electrochemical modification of a glassy carbon (GC) electrode with apigenin was carried out and the modified electrode was used for determination of copper(II) (Cu(II)) in soil samples. The GC was modified through the electrochemical polymerization of apigenin (PolyApi/GC) on the electrode surface in aqueous media. The electrode surface was modified with apigenin in phosphate buffer solution (PBS), pH 7, from 0 mV to +1400 mV potential ranges, using 100 mV s−1 sweep rate and 30 cycles by cyclic voltammetry (CV). The surface characterizations of this sensor electrode were performed by CV, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Britton-Robinson (BR) buffer solution at pH 5 was used for determination of Cu(II) by differential pulse voltammetry (DPV). The detection limit was obtained as lower as 1.0 × 10−11 M. By using this calibration curve, the amount of Cu(II) was determined as 7.34 × 10−7 M in soil samples. The results showed that pH, incubation time and interferences of some cations and anions were significant.

English

The redox characteristics of the drug Bicalutamide at a glassy-carbon electrode (GCE) was investigated for the first time in aqueous media by differential-pulse voltammetry (DPV) and cyclic voltammetry (CV). In Britton-Robinson (BR) buffer of pH 2.0-10.0, an irreversible and diffusion-controlled reduction voltagram were developed. The dependence of the CV response of the developed cathodic peak on the sweep rate ( �) and on depolarizer concentration was typical electrode-coupled chemical reaction mechanism (EC) in which an irreversible reaction is interposed between the charges. In BR buffer of pH 6 - 7, a well defined cathodic peak was developed and the plot of peak current height of the DPV against Bicalutamide concentration at this peak potential was linear in the range 1×10 �8 - 2.6 ×10 �5 M with lower limits of detection (LOD) and quantization (LOQ) of 8 x 10 -8 M and 1 ×10 �7 M, with good selectivity and sensitivity. A relative standard deviation (RSD) for Bicalutamide at a concentration of 4.5×10 �5 M was 2.48% (n=6). The proposed method was successfully applied to Bicalutamide determination in pharmaceutical samples and results are very good correlations with previously reported methods.

Voltammetric assay of anti‐anginal drug nicorandil in different solvents

Voltammetric behaviour and assay of nicorandil were investigated using square-wave and cyclic voltammetry. Voltammograms in Britton-Robinson (BR) buffer exhibited one well-defined and two merged reduction peaks. The influence of different buffers, electrolytes, pH, scan rates, and concentration of the drug on cathodic peak current was studied. On the basis of electrochemical behaviour of nicorandil, a direct square-wave voltammetric procedure for quantitation of nicorandil has been developed and validated. The proposed square-wave voltammetric method allows quantitation over the range 12.5-62.5 µg mL(-1) with correlation coefficient of 0.992. The limit of quantification and limit of detection were 21.95 µg mL(-1) and 6.58 µg mL(-1) , respectively. Precision and accuracy were also checked and found within limits. The developed square-wave method has also been successfully applied for the determination of nicorandil in pharmaceutical formulations.

Study on the ternary mixed ligand complex of palladium(II)–aminophylline–fluorescein sodium by resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectrum and its analytical application

The interaction between palladium(II)–aminophylline and fluorescein sodium was investigated by resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectrum. In pH 4.4 Britton–Robinson (BR) buffer medium, aminophylline (Ami) reacted with palladium(II) to form chelate cation([Pd(Ami)] 2+), which further reacted with fluorescein sodium (FS) to form ternary mixed ligand complex [Pd(Ami)(FS) 2]. As a result, resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering spectrum (FDS) were enhanced. The maximum scattering wavelengths of [Pd(Ami)(FS) 2] were located at 300 nm (RRS), 650 nm (SOS) and 304 nm (FDS). The scattering intensities were proportional to the Ami concentration in a certain range and the detection limits were 7.3 ng mL −1 (RRS), 32.9 ng mL −1 (SOS) and 79.1 ng mL −1 (FDS), respectively. Based on it, the new simple, rapid, and sensitive scattering methods have been proposed to determine Ami in urine and serum samples. Moreover, the formation mechanism of [Pd(Ami)(FS) 2] and the reasons for enhancement of RRS were fully discussed.

Determination of quantitative phenol in tap water samples as electrochemical using 3,3'-diaminobenzidine modified glassy carbon sensor electrode

In this paper, the amount of phenol in Meram, Karatay and Selçuklu regions in Konya tap water samples was quantified in aqueous medium by using 3,3'-diaminobenzidine (DAB) modified glassy carbon (GC) electrode. The electrode surface was modified with DAB in 0.1 M tetrabutylammonium tetrafluoroborate (TBATFB) using 100 mV s − 1 scanning rate between −0.5 V and + 1.5 V with 10 cycles. For the calibration curve, a series of standard phenol solution between 1.0 × 10 −12 M and 1.0 × 10 −3 M was prepared using pH 12. The prepared standard solutions were used for the chemical binding of phenol to the modified electrode surface between 0.0 V and + 1.1 V potential range using 100 mV s −1 scanning rate with 10 cycles. By using this calibration method, the amount of phenol was determined as 1.23 × 10 −10 M, 3.03 × 10 −8 M and 1.99 × 10 −9 M in natural tap water samples in Britton–Robinson (BR) buffer solution at pH 12. Detection limit was obtained as low as 1.0 × 10 −10 M. The presence of DAB, phenol at the GC surface and phenol of DAB modified GC electrode surface was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).

Study on the interaction between palladium(II)-chlorpromazine hydrochloride and sodium tungstate by the resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectra and its analytical application

The interaction between palladium(II)-chlorpromazine hydrochloride and sodium tungstate was investigated by ultraviolet-visible absorption, resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS) spectroscopy. In pH 5.3 Britton-Robinson (BR) buffer medium, chlorpromazine hydrochloride (CPZ) reacted with Pd(II) to form 2:1 cationic chelate, which further reacted with Na2WO4 to form a 1:1 ternary ion-association complex ([Pd(CPZ)2]·WO4). As a result, the signal intensities of RRS, SOS and FDS were enhanced greatly, and the enhancements of scattering were proportional to the CPZ concentration in a certain range. Their maximum wavelengths were located at 310 nm, 570 nm and 391 nm, respectively and the detection limits (3σ) were 1.6 ng/mL (RRS method), 3.2 ng/mL (SOS method) and 5.6 ng/mL (FDS method). The optimum reaction conditions, the influences of coexisting substances and analytical application were mainly investigated by RRS method due to its highest sensitivity. A highly sensitive, simple, rapid and new method had been proposed to determine CPZ in the pharmaceutical form and residue of CPZ in pork. In addition, the Gibbs free energy change (δGf) of ion-association reaction was computed by using B3LYP/3-21g*/LanL2dz method. The formation of ion-association and the reasons for the enhancement of RRS were also discussed.

Electrochemical Oxidation of Cytosine on Carbon Paste Electrode and Its Determination

AbstractIn this paper electrochemical oxidation of cytosine was investigated on a carbon paste electrode for the first time. In pH 5.0 Britton‐Robinson (B‐R) buffer solution a well‐define irreversible oxidation peak appeared at the potential of 1.480 V (vs. SCE), which indicated the electrooxidation of cytosine on the electrode. The electrochemical behaviors of cytosine were carefully investigated by cyclic voltammetry at the selected conditions. The electrochemical parameters such as electron transfer number (n), electron transfer coefficient (α) and electrode reaction standard rate constant (ks) was calculated with the results as 2.14, 0.15 and 1.049 × 10−3 s−1, respectively. Under the optimal conditions a good linear relationship was constructed between the cytosine concentration and the differential pulse voltammetric current in the range from 10.0 to 1000.0 μmol/L with the linear regression equation as Ip(μA) = 0.0519C (μmol/L) + 0.419 (γ = 0.999) and the detection limit as 1.9 μmol/L (3σ;).

Interaction of an antidepressant buzepide methiodide with DNA immobilized on the glassy carbon electrode

In the present study, a DNA-biosensor was prepared using immobilization technique to investigate the interaction between an antidepressant, buzepide methiodide (BZP) and calf thymus DNA. BZP showed a quasireversible peak in Britton–Robinson (BR) buffer of pH 5 at bare glassy carbon electrode (GCE). At DNA modified GCE, the peak potential of BZP was observed to be shifted towards positive potential revealing intercalative mode of binding. The binding constant and stoichiometry between DNA and BZP are calculated to be 1.908 × 10 5 M −1 and 0.982, respectively. The spectroscopic techniques viz., spectrofluorescence and UV–vis absorption have also been employed to understand the interaction between BZP and DNA. The results serve as a reference for the interaction of BZP with DNA base pairs in the natural environment of living cells.

Study on the Interaction between a Novel Ionic Liquid Probe and Anionic Surfactants Using Resonance Light Scattering Spectra and Its Analytical Application

AbstractThe interaction between anionic surfactants (AS) and 1‐hexadecyl‐3‐methylimidazolium bromide [C16mim]Br was studied by using resonance light scattering (RLS) technique, UV‐Vis spectrophotometry and fluorometric methods. In Britton Robinson (BR) buffer (pH 6.0), [C16mim]Br reacted with AS to form supermolecular complex which resulted in enhancement in RLS intensity. Their maximum RLS wavelengths were all at 390 nm. Some important interacting experimental variables, such as the solution acidity, [C16mim]Br concentration, salt effect and addition order of the reagents, were investigated and optimized. Under the optimum conditions, quantitative determination ranges were 0.001–7 μg·mL−1 for dodecyl sodium sulfate (SDS), 0.001–6 μg·mL−1 for sodium dodecylbenzene sulfonate (SDBS) and 0.005–7 μg·mL−1 for sodium lauryl sulfonate (SLS), respectively, while the detection limits were 1.3 ng·mL−1 for SDS, 1.0 ng·mL−1 for SDBS and 5.1 ng·mL−1 for SLS, respectively. Based on the ion‐association reaction, a highly sensitive, simple and rapid method has been established for the determination of AS.

Determination of Chondroitin Sulfate A by Resonance Rayleigh Scattering and Resonance Non-linear Scattering with Proteins as Probes

In a pH 2. 5 ～ 4. 0 Britton-Robinson( BR) buffer medium,some proteins such as bovine serum albumin( BSA) ,Chymotrypsin( Chy) and α-amylase( α-Amy) can react with chondroitin sulfate A( CS) via electrostatic force,hydrogen bond force or/and hydrophobic force to form binding products. As a result,the resonance Rayleigh scattering( RRS) ,second-order scattering( SOS) and frequency doubling scattering( FDS) were enhanced greatly with new scattering spectra appeared. The increments of scattering intensity( ΔI) were proportional to the concentration of CS in certain ranges. The detection limits( 3σ) of CS in Chy,BSA and α-Amy systems were 1. 4,2. 0 and 1. 8 μg/L( RRS method) ,2. 3,2. 9 and 2. 5 μg/L( SOS method) ,5. 8,13. 2 and 9. 6 μg/L ( FDS method) ,respectively. Among them,the RRS method exhibited the highest sensitivity and the Chy-CS system was more sensitive than others. The characteristics of the spectra and optimal conditions of RRS method were investigated. The effects of external substances were tested. The established methods have a good selectivity and can be applied to the determination of CS in eye drops with satisfactory results.

Determination of anionic surfactant in surface water by resonance light-scattering technology

A sensitive and rapid method, without any extraction procedure, for the determination of the anionic surfactant expressed in the terms of sodium dodecyl benzene sulfonate (SDBS) by the resonance light scattering (RLS) technique is described in this paper. In the pH value 3.0 Britton-Robinson (BR) buffer, Victoria blue B (VBB) reacted with SDBS and produced large particles which resulted in the remarkable enhancement of the RLS intensity of VBB. The enhanced RLS intensity of the assay system was proportional to the concentration of SDBS in the range of 0.08–3.0 mg L–1 and the correlation coefficient was r = 0.9996. The detection limit was 0.013 mg L–1. This method was applied to determine the anionic surfactant in the surface water samples and satisfactory results were obtained. The reaction mechanism was also studied and the interaction between VBB and SDBS was mainly governed by electrostatic effect and the π–π stacking effect.

Direct electrochemistry of hemoglobin in a nafion and CuS microsphere modified carbon ionic liquid electrode and its electrocatalytic behavior

Direct electrochemistry of hemoglobin (Hb) was realized on a Nafion and CuS microsphere composite film modified carbon ionic liquid electrode (CILE) with N-butylpyridinium hexafluorophosphate (BPPF6) as binder. Scanning electron microscopy (SEM), UV-Vis absorption spectroscopy and cyclic voltammetry were used to characterize the fabricated Nafion/CuS/Hb/CILE. Experimental results showed that a pair of well-defined quasi-reversible redox peaks appeared with the formal potential as -0.386 V (vs. SCE) in pH 7.0 Britton-Robinson (B-R) buffer solution, which was attributed to the Hb heme Fe(III)/Fe(II) redox couples. The electrochemical parameters of Hb in the composite film were carefully investigated with the charge transfer coefficient (α), the electron transfer number (n) and the electron transfer rate constant (ks) as 0.505, 1.196 and 0.610 s -1 , respectively. The composite film provided a favorable microenvironment for retaining the native structure of Hb. The presence of CuS microspheres showed great improvement on the electron transfer rate of Hb with the CILE, which maybe due to the contribution of specific characteristics of CuS microspheres and the inherent advantages of ionic liquid on the modified electrode. The fabricated Hb modified electrode showed good electrocatalytic ability in the reduction of H2O2. The proposed bioelectrode can be used as a new third generation H2O2 biosensor.

Absorption Spectra of Reaction System of Tetracaine Hydrochloride with Erythrosin and Its Analytical Application

In a Britton-Robinson ( BR) buffer solution of pH = 4. 0,erythrosine reacted with tetracaine hydrochloride( TC.HCl) to form a 1∶1 ion-association complex. As a result the absorption spectra of solution changed,and an obvious fading peak at 516 nm and a coloring revealing peak at 558 nm appeared. In the range of 0. 1 × 10 -6 to 7. 2 × 10 -6 g/mL,there is linearity between the concentration of TC.HCl and absorbency of the solution at the fading peak and coloring revealing peak. Based on it,a new spectrophotometry for the determination of TC.HCl was proposed. The molar absorptivity is 3. 30 × 104 L/( mol.cm) for the fading method,2. 22 × 104 L/( mol.cm) for the revealing method and 5. 52 × 104 L/( mol.cm) for the dualwavelength method. The optimum reaction conditions and primary chemistry characteristics were discussed. The reaction mechanism was dicussed by quantum chemistry AM1 method. The method has been applied to the determination of TC.HCl in human serum and urine samples with satisfactory results. The mean recovery is from 98. 1% to 103. 3%.

Part 1. Spectrophotometric determination of trace mercury (II) in dental-unit wastewater and fertilizer samples using the novel reagent 6-hydroxy-3-(2-oxoindolin-3-ylideneamino)-2-thioxo-2H-1,3-thiazin-4(3H)-one and the dual-wavelength β-correction spectrophotometry

A simple and low cost method was developed and validated for the determination of trace mercury (II) ions in dental-unit wastewater and fertilizer samples. The method was based upon the reaction of mercury (II) ions with the novel reagent 6-hydroxy-3-(2-oxoindolin-3-ylideneamino)-2-thioxo-2H-1,3-thiazin-4(3H)-one, the formed complex shows an absorption maximum at 505 nm (lambda(max)) in Britton-Robinson (B-R) buffer (pH 4-6).The corrected absorbance of the formed complex at lambda(max) was obtained employing beta-correction spectrophotometric method. Beer's-Lambert law and Ringbom's plots of the colored Hg-reagent complex were obeyed in the concentration range of 0.2-2.0 and 0.32-0.96 microg mL(-1) mercury (II) ions, respectively with a relative standard deviation in the range of 2.1+/-1.3%. The limits of detection (LOD) and quantification (LOQ) of the procedure were 0.026 and 0.086 microg mL(-1) Hg(2+), respectively. The proposed method was applied for the analysis of mercury (II) in dental-unit wastewater and fertilizer samples. The validation of the method was tested by comparison with the data obtained by the inductively coupled plasma-mass spectrometry (ICP-MS). The statistical treatment of data in terms of Student's t-tests and variance ratio f-tests has revealed no significance differences.

Voltammetry of resazurin at a mercury electrode

AbstractElectrochemical behavior of resazurin on HMDE in Britton-Robinson (B-R) buffers (pH 2.0–10.0) was studied using the square-wave voltammetry (SWV), square-wave adsorptive stripping voltammetry (SWAdSV), and cyclic voltammetry (CV) techniques. The voltammogram of resazurin in B-R buffer at pH < 4.0 exhibited two cathodic reduction peaks. The voltammetric peaks were obtained at −0.144 V (reversible) and −1.250 V (irreversible) at pH 3.2, and correspond to the reduction of resorufin to dihydroresorufin and to the catalytic hydrogen wave, respectively. At pH > 4.0, a new irreversible cathodic reduction peak, assigned to the protonation of N-oxide on the phenoxazin ring, was observed. Electrochemical parameters (I p/E p, I p/v, I p/pH, I p/t acc) of the compound were determined. From the voltammetric data, electrochemical reduction mechanisms for all peaks have been suggested. Maximum peak current for the reversible peak was obtained at pH 4.1. A linear relationship between the current and concentration was determined, and also the lowest detection limit was found as 3.25 × 10−8 mol L−1 and 1.98 × 10−10 mol L−1 for SWV and SWAdSV, respectively.

Utility of Ion-Pair and Charge Transfer Complexation for Spectrophotometric Determination of Domperidone and Doxycycline in Bulk and Pharmaceutical Formulations

Four simple, sensitive, and accurate spectrophotometric methods (A-D) have been developed for the determination of domperidone (I) and doxycycline (II) in bulk and in pharmaceutical formulations. The first two methods (A and B) are based on the formation of yellow ion-pair complexes between the examined drugs with bromocresol green (BCG) and methyl orange (MO) as chromophoric reagents in Britton-Robinson (B-R) universal buffer of pH 3.0 and 2.2, respectively. The formed complexes were extracted with chloroform and measured at 420 nm and 424 nm for I and II using BCG, respectively and 480 nm for the studied drugs using MO. The last two methods (C and D) are based on charge transfer complex formation between the studied drugs and tetracyanoethylene (TCNE); and 7,7,8,8-tetracyanoquinodimethane (TCNQ). Different variables affecting the reactions were studied and optimized. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9992 - 0.9998) were found between the absorbance and the concentration of I in the range of 1.4-22.4μg mL −1 , whereas that for II in the range 1.4-25.5μg mL −1 . For more accurate analysis, Ringbom optimum concentration range was found to be between 3.0-21.5 and 3.0-23.5μg mL −1 , for I, and II, respectively. Sandell’s sensitivity, correlation coefficient, and limits of detection and quantification were calculated for each method. A Job’s plot of the absorbance versus the molar ratio of drug to each of formed complex under consideration indicated (1:1) ratio. No interference was observed from common pharmaceutical excipients and additives. Statistical comparison of the results with those obtained by the official method shows excellent agreement and indicates no significant difference in accuracy and precision.