BR Buffer Solution Research Articles

Sensing ivacaftor accomplished using the square-wave voltammetric technique with the assistance of a cationic surfactant on a boron-doped diamond electrode

This investigation aims to describe the voltammetric analysis of ivacaftor (IVA) by utilizing the boron-doped diamond (BDD) electrode to add a cationic surfactant. Cyclic voltammetry via Britton-Robinson (BR, 0.04 mol L−1, pH 2.0) buffer was used to perform determinations of the IVA demonstrating irreversible behaviors, adsorption-controlled and well-defined (+1.04 V, PA1) and an ill-defined (+1.42 V, PA2) oxidation peaks (vs. Ag/AgCl). The findings revealed that the oxidation peaks of IVA are pH-dependent (ranging from 2.0 to 5.0). The use of cetyltrimethylammonium bromide (CTAB, cationic surfactant) in the chosen supporting electrolyte enormously raised the oxidation peak currents of IVA. For the measurement of IVA in a 0.04 mol L−1 BR buffer solution with a pH of 2.0, the linear relationship was discovered to exist under the conditions of the experimental optimal parameters involving 2 × 10−4 mol L−1 CTAB at +1.11 V (vs. Ag/AgCl) (after an accumulation of 60 s at the open-circuit condition). The linear concentration was discovered using 0.25 to 10.0 μg mL−1 (6.4 × 10−7-2.5 × 10−5 mol L−1) and the limit of detection 0.073 μg mL−1 (1.9 × 10−7 mol L−1). The devised methodology was effectively employed to determine IVA in pharmaceutical formulation. To the best of our understanding, it represents the first electroanalytical method for detecting IVA by voltammetry.

Development of environmentally friendly voltammetric methods for the individual and simultaneous determination of antihypertensives: Validation and application

In this study, voltammetric methods were developed and validated for the individual determination of lisinopril (LSNP) and its association with hydrochlorothiazide (HCTZ) employing a cathodically pretreated boron-doped diamond (CP-BDD) electrode. The studies of the experimental and instrumental parameters that affect the performance of both methods were carefully carried out by optimizing each parameter. The methods were validated by evaluating the figures of merits recommended by the validation guidelines. The method for the individual determination of LSNP presented a linear working range between 9.99 and 196.01 nmol L−1, with a limit of detection of 3.05 nmol L−1 by differential pulse voltammetry in BR buffer solution (pH 2.0). Simultaneous analytical curves over the concentration ranges of 0.40–3.99 and 0.050–1.045 μmol L−1 for HCTZ and LSNP, respectively, were obtained by square-wave voltammetry in Britton-Robinson buffer solution (pH 3.0). The limit of detection values calculated were 0.052 μmol L−1 and 0.020 μmol L−1, respectively for HCTZ and LSNP. The sensitivity observed for individual analytical curves of HCTZ and LSNP was statistically equal to that obtained for the simultaneous analytical curves at the 95 % confidence level. The developed methods were applied to determine these drugs in environmental, biological, and pharmaceutical samples, with satisfactory results. The method's greenness was assessed demonstrating that both validated methods constitute a greener alternative to conventional analytical methods reported in the literature.

Optimization of voltammetric parameters for sensitive and simultaneous determination of ferulic acid and vanillin using a glassy carbon electrode based on 2-aminonicotinic acid in the presence of surfactant media

The electrochemical sensor for simultaneous determination of ferulic acid (FA) and vanillin (VA) was prepared by electrochemical deposition of 2-aminonicotinic acid (2-ANA) on the glassy carbon (GC) electrode. The voltammetric determination of FA and VA was performed in the BR buffer solution in the presence of sodium dodecyl sulfate as a surfactant with SWV. The parameters of the SWV technique were optimized by response surface methodology experimental design. Under optimized conditions, the 2-ANA/GC modified electrode presented a linear working range of 2.8 × 10−8 M to 7.50 × 10−6 M and 7.50 × 10−6 M to 2.45 × 10−5 M for FA, 3.06 × 10−8 M to 1.27 × 10−5M for VA. The detection limit (LOD) values for FA and VA were 6.87 nM and 9.23 nM, respectively. Using the 2-ANA/GC sensor, concentrations of FA and VA in instant coffee and milk samples were determined with %recovery values between 103.40 and 97.07 and %RSD values between 0.76 and 4.40.

Electrochemical determination of aripiprazole based on aluminium oxide nanoparticles modified carbon paste electrode.

The electrochemical oxidation of aripiprazole was explored at a carbon paste electrode modified with aluminium oxide nanoparticles by cyclic voltammetry and square-wave anodic adsorptive stripping voltammetry. Experimental parameters such as carbon paste composition, scan rate, buffer pH, accumulation time, and accumulation potential were optimized in order to obtain high analytical performance. The incorporation of aluminium oxide nanoparticles into the carbon paste matrix enhanced the effective surface area of the carbon paste electrode and improved the sensitivity. On the aluminium oxide nanoparticles modified carbon paste electrode, aripiprazole exhibited an irreversible anodic peak at +1.17 V in pH 1.8 BR buffer solution. Under optimum conditions, the peak current exhibited a linear dependence with aripiprazole concentration between 0.03 and 8.0 μM with a detection limit of 0.006 μM. The analytical applicability of the voltammetric method was evaluated by quantification of ARP in human serum samples and pharmaceutical formulations.

Resonance Rayleigh scattering method for highly sensitive detection of copper ions in water based on salicylaldeoxime-copper (Ⅱ)- 2-methylimidazole supramolecular

In weakly acidic BR buffer solution, a convenient and sensitive resonance Rayleigh scattering (RRS) method for the detection of Cu(Ⅱ) was developed based on the formation of salicylaloxime-Cu(Ⅱ) supramolecular complex by complexation reaction. The coordination reaction of salicylaldehyde oxime with Cu(Ⅱ) led to the significant enhancement of the resonance Rayleigh scattering intensity of the solution, and the increase of the resonance Rayleigh scattering intensity was proportional to the concentration of Cu (Ⅱ). When organic compounds with different molecular structures were introduced into the system, the resonant Rayleigh scattering intensity of the solution system changed differently. The interaction between the compounds and the spatial structure of the complexes were characterized by transmission electron microscopy (TEM), Fourier real-time infrared spectroscopy (FT-IR), zeta potential and particle size. The results showed that when 2-methylimidazole was introduced, the layered texture of Cu(Ⅱ)-CH3COO--H2PO4- -salicylaldoxime system changed to porous reticular spatial structure, and the RRS value increased significantly. Under the optimal conditions, in the range extending from 0.08 to 2.81 µmol/L, the equation of linear regression was ΔI = 3202c + 10.88 (c, µmol/L) with a correlation coefficient 0.9996, and the detection limit was estimated to be 4.23 × 10-2 µmol/L. The method was successfully applied for the determination of Cu(Ⅱ) in tap and river water sample, suggesting its great potential toward Cu(Ⅱ) analysis.

Electrochemical determination of phosphodiesterase-3 enzyme inhibitor drug Milrinone with nanodiamond modified paste electrode

Milrinone (MIL) is an essential cardiac inotrope drug for cardiovascular disease. In this study, a simple nanosensor based on a nanodiamond carbon paste electrode modified with flower-like ZnO particles was developed to determine MIL electrochemically rapidly and accurately. The flower-like ZnO nanoparticles were synthesized by a simple and cheap sonochemical method. The structure and morphology of the ZnO nanoparticles were investigated by Fourier transform infrared spectrometer and scanning electron microscopy. The electron transfer properties of bare carbon paste electrodes, nD@CPE, CPE/ZnO, and flower-like carbon paste electrodes modified with ZnO and decorated with nanodiamonds (nD@CPE/ZnO) were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was confirmed that the nanosensor, which was electrochemically characterized by EIS and CV, was designed to increase electrical conductivity and facilitate electron transfer upon the modification of CPE with nanomaterials. The electrochemical behavior of MIL on the modified electrode was investigated by differential pulse voltammetry (DPV). Owing to the developed nD@CPE/ZnO nanosensor, the peak current of 10 µM MIL in pH 4.0 BR buffer solution was found to be approximately 19 times higher in DPV compared to bare CPE. Under optimum conditions, the constructed nanosensor offered a linear calibration curve of concentration ranging from 0.2 to 10 µM with the detection limit (LOD) and quantification limit (LOQ) 41 nM and 136 nM, respectively, for MIL in pH 4.0 Britton Robinson buffer solution. The same electrode was used for stability control after 7 days and its current response was found to decrease to 96.7%. The developed method was successfully used for the determination of MIL in human serum and urine samples. The method based on the use of modified nD@CPE/ZnO, showed linearity from 0.6 to 10 µM in serum and 0.8–10 µM in urine. LOD values were found as 128 nM and 176 nM in serum and urine samples, respectively. According to these results, this optimized method showed reasonable sensitivity for the determination of MIL in serum and urine samples.

Developing an electroanalytical procedure for the determination of caffeic acid phenethyl ester at a boron-doped diamond electrode by the use of cationic surfactant media

The aim of the present work is to describe voltammetric analysis of caffeic acid phenethyl ester (CAPE) by using a boron-doped diamond (BDD) electrode in the presence of the cationic surfactant. Using cyclic voltammetry, CAPE demonstrated a single well-defined, quasi-reversible, adsorption-controlled by oxidation and reduction peak at approximately +0.44 V & +0.22 V respectively, (vs. Ag/AgCl) in the Britton-Robinson buffer (BR, 0.04 mol L−1, pH 5.0). The obtained results showed that the oxidation peaks of CAPE are pH dependent (ranging from 2.0 to 6.0). The oxidation peak currents of CAPE were significantly increased by using cetyltrimethylammonium bromide (CTAB, cationic surfactant) in the selected supporting electrolyte. Under the optimum parameters of experiment, the linear relationship was found for CAPE determination in 0.04 mol L−1 BR buffer solution (pH 5.0) including 1 × 10−4 mol L−1 CTAB at +0.41 V (vs. Ag/AgCl) (after 30 s accumulation at the open-circuit condition). The linear range was found with 0.01 to 1.0 μg mL−1 (3.5 × 10−8–3.5 × 10−6 mol L−1) via the detection limit 0.0028 μg mL−1 (9.8 × 10−9 mol L−1). The developed approach was used successfully to detect CAPE concentration in the model urine samples. To our knowledge, this is the first approach for electrochemically analyzing of CAPE.

Preparation of mixed-valent manganese-vanadium oxide and Au nanoparticle modified graphene oxide nanosheets electrodes for the simultaneous determination of hydrazine and nitrite

• Mixed valent metal–metal oxides were performed by SEM-EDX, XPS, CV, EIS techniques. • Simultaneous and individual determination of hydrazine and nitrite. • LOD for LSV 3.0 and 10.0 µM for hydrazine and nitrite, respectively. • AuNP/MnOx-VOx/ERGO was tested in river water and food samples. In this study, for the first time in the literature, simultaneous and individual determination of hydrazine and nitrite have performed by combining the triple electrocatalytic properties of electrochemically reduced graphene oxide (ERGO), multivalent metal oxide (MnOx-VOx) films and gold nanoparticles (AuNPs). Characterization studies of AuNP/MnOx-VOx/ERGO electrode were performed using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) methods. The determinations of hydrazine and nitrite in pH 8 BR buffer solution were studied using linear sweep voltammetry (LSV) and amperometry methods. The limit of detection (LOD) for simultaneous detection was 3.0 and 10.0 µM for hydrazine and nitrite, respectively, and the LOD for amperometric detection was 0.1 and 0.33 µM, respectively. AuNP/MnOx-VOx/ERGO electrode was tested for the determination of hydrazine and nitrite in river water and food samples, and this electrode provides a recovery of 91.0% to 113.0%. Also, the electrode has practical preparation, good repeatability, selectivity, accuracy.

A modified sensitive palladium-copper oxide and multiwalled carbon nanotubes electrochemical sensor for detection of ametridione pesticide

Glassy carbon electrode modified sensitive Pd-CuO/MWCNTs electrochemical nanosensor was used for detection of ametridione pesticide in water samples. The morphology characteristics of Pd-CuO/MWCNTs are examined by scanning electron microscopy and EDX. The ametridione pesticide under voltammetric investigation involves irreversible, 4e? electron reduction based on the protonation of the two carbonyl groups (>C=O). The voltammetric method was applied for the detection of ametridione in BR buffer solution at pH 5.0 as a supporting electrolyte. The detection limit, limit of quantification and concentration ranges of the proposed method were 0.0796 ?g?mL?1 (signal/noise=3), 0.5560 ?g?mL?1 and 0.1 to 10.0 ?g?mL?1, respectively. The electrochemical sensor was successfully applied for the detection of ametridione in tap, agricultural run-off and river water samples showing >98% mean recoveries.
 

Investigation of electrochemical oxidation mechanism, rapid and low-level determination for whitening cosmetic: arbutin in aqueous solution by nano sepiolite clay

Arbutin (AR) is one of the important chemical agents that has the lack of adverse effects in cosmetic applications, which has still biological importance and the increasing interest toward arbutin in the cosmetic industry. Electrochemical sensors have received much attention because of their high sensitivity, simplicity, and fast. In this work, an electroanalytical method has been developed and validated for the quantification of AR on nano sepiolite-clay carbon paste electrode. The electrochemical oxidation mechanism of AR was also investigated in the aqueous medium. Nano-sepiolite clay modified carbon paste electrode was used as rapid and the low-level electrochemical sensor for determination of AR. The electrochemical responses of AR were compared on the surfaces of the bare and nano sepiolite modified carbon paste electrode using the cyclic voltammetric method in the BR buffer solution. The results showed the superior electrocatalytic performance on the peak current of AR at the modified carbon electrode. The stripping conditions and experimental parameters (pH, the effect of modifier content, accumulation potential, and time) were optimized to obtain the best oxidation signal of AR. Under the optimized conditions, linear calibration curves were obtained in the concentration range of 0.0362–80.0 µM (with the detection limit of 10.8 nM) with square-wave adsorptive stripping voltammetry. The method was successfully applied for the determination of AR in the cosmetic Tritone cream sample. This work confirms thus that electrochemical sensors may be the potential future candidate for rapid, sensitive, low-level, and reproducible analysis.

Easily Prepared Co3O4Doped Porous Carbon Material Decorated with Single‐wall Carbon Nanotubes Applied in Voltammetric Sensing of Antioxidant α‐lipoic Acid

AbstractThe homemade, porous carbon material, thermolysis prepared from Novolac phenol‐formaldehyde resin, in situ modified with Co3O4nanoparticles and mixed with single‐wall carbon nanotubes, was used in selective sensing of prominent antioxidant α‐lipoic acid (LA). XRD, SEM and EIS measurements were used for characterization of material composition, structure, morphology and improved conductivity. The quantification of LA at TPCo3O4&SWCNTCPE was done by a square‐wave voltammetric technique in BR buffer solution at pH 6. The linear working range was recorded from 2 to 100 μM of LA and the proposed electrode material was successfully applied in the determination of LA in dietary supplements.

Development of an electroanalytical methodology using differential pulse voltammetry for amiloride determination

In this work, an analytical electrochemical method was developed using a glassy carbon electrode (GCE) for the determination of amiloride (AMI). To study the electrochemical behavior of AMI, the cyclic voltammetry and differential pulse voltammetry techniques were used, adding a AMI solution in 0.1 mol L−1 BR buffer solution (pH 2.0) to the electrochemical cell. A reversible AMI oxi-reduction process was revealed in the scan rate of + 0.4 to − 0.1 V. The DPV parameters optimized were the scan rate (10 mV s−1) and amplitude (70 mV). After parameters optimization, the linear working range was from 9.90 to 90.9 μmol L−1, with detection limit of 5.19 μmol L−1 and quantification limit of 17.3 μmol L−1. The validity of the electroanalytical method for the determination of AMI in biological fluids (urine and serum) was demonstrated. The proposed method is advantageous due to its good sensitivity, speed, simplicity, precision, and accuracy towards AMI quantification.

Electrochemical Performance of pH Sensor Based on LbL Films of Polyaniline-Gum Arabic Nanocomposite and Graphene Oxide

Miniaturized pH sensors have attracted the attention mostly due to their applications for monitoring chemical and biological processes. The modification of electrodes by Layer-by-Layer (LbL) technique results in films with nanometric structure for application in devices with different sizes. In this paper, an electrode modified with LbL films of polyaniline-gum Arabic nanocomposite (PANI-GA) and graphene oxide (GO), designed (PANI-GA/GO)3, was applied as a potentiometric pH sensor based on states of oxidation PANI. The pH measurements were performed in BR buffer solution and a linear range was observed from pH 2 to 7. The detection limit (DL) and quantification limit (QL) were of pH = 0.465 and 1.55, respectively. Analytical curves were obtained in triplicate and inter-assay precision was calculated for the system, demonstrating good results with relative standard deviation (RSD) of 3.7% for five measurements in different days. The (PANI-GA/GO)3 LbL film showed promising results for its use in the development of potentiometric pH sensor.

Determination of tramadol in pharmaceutical forms and urine samples using a boron-doped diamond electrode

The present work describes the electroanalytical investigation and a novel voltammetric method for the cheap, fast and simple quantification of tramadol (TRH) using a boron-doped diamond electrode. TRH displayed one well-defined, irreversible and adsorption-controlled oxidation peak at about 1.58 V (vs. Ag/AgCl) in Britton?Robinson buffer (BR, 0.1 mol L-1, pH 3.0) using the cyclic voltammetry technique. The voltammetric responses of the oxidation peaks are dependent on pH and their sensitivity was significantly enhanced in the presence of surfactant media (sodium dodecyl sulphate, SDS). Under the optimized experiment conditions, employing the square-wave stripping mode, it was found that there was an excellent correlation between oxidation peak current and the TRH concentration in the range 0.25 to 50.0 ?g mL-1 (8.34?10-7?1.67?10-4 mol L-1), with a detection limit of 0.072 ?g mL-1 (2.40?10-7 mol L-1) in 0.1 mol L-1 BR buffer (pH 3.0) solution comprising 8?10-4 mol L-1 SDS at 1.52 V (after 30 s accumulation at open-circuit conditions). The developed approach could be used for the quantification of TRH in pharmaceutical formulations and spiked human urine samples with acceptable recoveries.

Electrochemical evaluation and voltammetric determination of laxative drug bisacodyl on boron-doped diamond electrode

Electroanalytical chemistry plays a very important role concerning the development of environmentally friendly and time-saving analytical methods. This work reports the first voltammetric determination of bisacodyl (BIS) using boron-doped diamond electrode (BDDE). On the cathodically pretreated BDDE, BIS presented an irreversible and diffusion controlled anodic peak at 1.55 V (vs Ag/AgCl (3.0 mol L–1 KCl)) in BR buffer solution (pH 5.0). Using optimized experimental conditions, the anodic current was linear with the BIS concentration range of 1.00–44.0 μmol L–1, with limit of detection of 0.343 μmol L–1. The viability of the proposed method was successfully evaluated by quantification of BIS in commercial pharmaceutical formulations and the accuracy of the developed analytical procedure was statistically proven by comparison with a validated spectrophotometric method.

Study on Dissociation Equilibria of Eberconazole Nitrate in Micellar Media by Spectrophotometry

The equilibrium dissociation constant (KD) is the basic parameter to evaluate the binding property of the chemical structure of compounds. Thus, a variety of analytical methods have been established to determine the KD values, including radioligand binding assay, surface plasmon resonance method, fluorescence energy resonance transfer method, affinity chromatography, and isothermal titration calorimetry. Here we present a detailed overview of the dissociation equilibria of Eberconazole nitrate (EBZ) in homogeneous and heterogeneous systems, focusing primarily on methods that are based on spectrophotometrically of the dissociation reaction. The Dissociation equilibria of Eberconazole nitrate (EBZ) in homogeneous and heterogeneous systems were studied spectrophotometrically in Britton-Robinson’s (BR) buffer at 25°C. Acidity constant of EBZ in BR buffer was found to be 9.5. The effect of anionic, cationic and non-ionic surfactants applied in the concentration exceeding critical micellar concentration (cmc) on acid – base properties of EBZ were also examined. The results revealed a shift of pKa values in micellar media comparing to the values obtained in BR buffer. These shifts in pKa values are more in cationic and anionic micellar media compared with that of non-ionic. The observed differences in pKa values between micellar media and BR buffer solution ranged between -6.0 to -2.0 units. The micellar-mediated pKa shifts can be attributed to the differences between the mean intrinsic solvent properties of the interfacial and bulk phases, with an additional contribution from the electrostatic micellar surface potential in the case of the charged aqueous micellar solutions.

Simultaneous Electrochemical Evaluation of Ascorbic Acid, Epinephrine and Uric Acid at Disposable Pencil Graphite Electrode: Highly Sensitive Determination in Pharmaceuticals and Biological Liquids by Differential Pulse Voltammetry.

As is known, AA, EP and UA can also coexist in biological fluids. Therefore, the determination of the levels of these compounds in biological fluids is extremely important both for the diagnosis and treatment of the related diseases. In the presence of many interfering substances in biological fluids such as blood and urine samples, it is very important that these compounds can be selectively analyzed. All electrochemical experiments were performed using an Autolab PGSTAT 128N potentiostat. Before beginning the electrochemical measurements, the PGE was activated. The electrochemical pretreatment of PG was exercised by anodically +1.40 V for 60 s. Then, measurements were performed with CV (-0.4 V to 1.2 V) and DPV (-0.2 V to 0.7 V) for single and simultaneous voltammetric behaviour of AA, EP, and UA in the electrochemical method. The anodic peak potentials of AA and UA were observed at about +0.32 V and +0.62 V, respectively. On the other hand, for EP, while anodic peak potential was observed at about +0.53 V, in the reverse scan, cathodic peak potentials were observed at about +0.41 V and +0.007 V. The reduction peak observed at +0.3 V with the oxidation peak observed at +0.53 V are the reversible peaks. In the method developed for the electrochemical simultaneous determination of AA, EP and UA using PGE with DPV technique in BR buffer solution (pH 4.0), the anodic peak potentials are sufficiently separated from each other. A voltammetric method was developed for the simultaneous determination of AA, EP and UA with PGE for the first time. Here, the most important thing is that the simultaneous determination of AA, EP and UA was successfully achieved with that targeted voltammetric method which was sensitive, low-cost, practical and well-repeated; and that these were proven to be selectively applicable in pharmaceutical products and biological liquids.

Glassy carbon electrode modified with a nanocomposite of multi-walled carbon nanotube decorated with Ag nanoparticles for electrochemical investigation of Isoxsuprine

A highly sensitive voltammetric sensor is prepared using multi-walled carbon nanotube decorated with silver nanoparticles (AgNPs-MWCNTs) and is applied for the determination of Isoxsuprine (ISOX). The characterization of the prepared nanocomposite is performed using energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscope (TEM), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry techniques. The electrochemical behavior of ISOX is studied on the surface of the modified electrode by linear sweep and cyclic voltammetry methods. Under the optimized conditions such as pH of the supporting electrolyte, accumulation time and amount of the casted modifier, a significant electrochemical improvement is observed toward the electro-oxidation of ISOX on the surface of AgNPs-MWCNTs glassy carbon electrode (AgNPs-MWCNTs/GCE), in comparison to MWCNTs/GCE and bare GCE. At the surface of the modified electrode two oxidation peaks are observed for ISOX at potentials around 0.63 V (peak I) and 0.82 V (peak II) in BR buffer solution of pH 7.0. By using two anodic peaks of ISOX, two linear dynamic ranges of 0.04–5.0 μmol L−1 and 0.2–5.0 μmol L−1 with detection limits of 12 nmol L−1 and 60 nmol L−1are obtained for peaks I and II, respectively. The modified electrode showed a simple fabrication procedure, high sensitivity, stability and good reproducibility in response to ISOX. The AgNPs-MWCNTs/GCE is successfully applied for the accurate determination of trace amounts of ISOX in pharmaceutical and clinical preparations.

Study on simultaneous determination of three nitroimidazole residues in honey by high performance liquid chromatography–resonance Rayleigh scattering spectra

A novel and high sensitivity method that high performance liquid chromatography combined with resonance Rayleigh scattering is established for the determination of nitroimidazole residues in honey, including Metronidazole (MNZ), Ornidazole (ONZ) and Tinidazole imidazole (TNZ). In pH 3.8 BR buffer solution, the three nitroimidazole drugs separated by HPLC, and then reacted with a post-column derivatization Phloxine B (PB) in the reaction tube to form 1:1 ion-association complex, which Leads to significant enhancement of the RRS signal. This paper optimized the experimental conditions of post-column derivation and discussed the mechanism of reaction for the enhancement of RRS signal. Under the optimal experimental conditions, the RRS signals of the three nitroimidazole drugs were enhanced with the increase of its concentration in the respective linear range. The detection limit (S/N) of MNZ, ONZ and TNZ was: 0.013 μg·mL−1, 0.049 μg·mL−1 and 0.27 μg·mL−1, respectively. The recovery rate was 97.4%–102.2%, and the relative standard deviation (RSD) does not exceed 5.3%, the reliability of this technique is verified, and the result of this method is satisfyingly.

Preparation and characterization of a carbon nanotube-based ceramic electrode and its potential application at detecting sulfonamide drugs

In this work, we report the construction, characterization, and the potential application of carbon-ceramic electrodes prepared with functionalized multi-walled carbon nanotubes (CCE/f-MWCNT) to detect two sulfonamide drugs: sodium sulfacetamide (SFC) and sulfadiazine (SFD). Prior to the construction of CCE/f-MWCNT, MWCNT samples were functionalized by using an acid treatment (HNO3/HClO4), and then characterized by FTIR spectroscopy, XRD, FESEM, and Raman spectroscopy. These techniques were also employed to characterize the prepared carbon-ceramic electrodes, and the obtained results demonstrated that the MWCNT were properly dispersed in the silica matrix. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy experiments showed that the f-MWCNT could enhance the electrochemical performance of the electrodes, as a consequence of its high electrical conductivity and large surface area. The antibacterial drugs were determined with CCE/f-MWCNT by employing CV and differential pulse voltammetry (DPV). A linear relationship between DPV peak currents and SFC and SFD concentrations was verified separately in the range from 9.9 to 177.0 µmol L− 1 in 0.04 mol L− 1 BR buffer solution pH 6.0. Detection and quantification limits were found to be 1.06 and 3.54 µmol L− 1 for SFC and 2.31 and 7.71 µmol L− 1 for SFD, respectively. Besides the good sensitivity, the CCE/f-MWCNT showed reproducibility and specificity, since its response was not significantly affected by the presence of electroactive interfering compounds. The promising analytical performance of the CCE/f-MWCNT was confirmed by determining SFC and SFD in commercial veterinary formulations, with percent recoveries ranging from 99.9 to 101.1% for SFC and from 99.8 to 102.2% for SFD.