Britton-Robinson Buffer Research Articles

Synthesis of pH-Sensitive Nitrogen-Doped Carbon Dots with Biological Imaging Function and Their Application in Cu2+ and Fe2+ Determination by Ratiometric Fluorescent Probes.

pH-sensitive nitrogen-doped carbon dots (N-CDs) were synthesized using immature seeds of elm trees as a carbon source and ethylenediamine as a coreactant through a facile one-step hydrothermal method. The N-CDs were characterized using fluorescence spectroscopy, fluorescence lifetime, ultraviolet-visible absorption, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy, as well as transmission electron microscopy. The N-CDs displayed excellent fluorescence properties and responded to pH changes. The N-CDs exhibited low toxicity and good biocompatibility and had the potential to be used for the biological imaging of HeLa cells and mung bean sprouts. Utilizing the mechanism of fluorescence resonance energy transfer, ratiometric fluorescent probes were prepared by simple mixing of N-CDs and fluorexon in a Britton-Robinson buffer solution. The ratiometric fluorescent probe was used to detect Cu2+ and Fe2+. The linear equations were RCu = -0.0591[Q] + 3.505 (R2 = 0.992) and RFe = -0.0874[Q] + 3.61 (R2 = 0.999). The corresponding limits of detection were 0.5 and 0.31 μM, respectively. The good results had been obtained in the actual samples detection.

The Effect of Rare-Earth Elements on the Morphological Aspect of Borate and Electrocatalytic Sensing of Biological Compounds.

Adjusting the morphological characteristics of a material can result in improved electrocatalytic capabilities of the material itself. An example of this is the introduction of rare-earth elements into the borate structure, which gives a new perspective on the possibilities of this type of material in the field of (bio)sensing. In this paper, we present the preparation of borates including La, Nd and Dy and their application for the modification of a glassy carbon electrode, which is used for the non-enzymatic detection of a biologically relevant molecule, vitamin B6 (pyridoxine). Compared with the others, dysprosium borate has the best electrocatalytic performance, showing the highest current and the lowest impedance, respectively, as determined using cyclic voltammetry and impedance tests. Quantitative testing of B6 was performed in DPV mode in a Britton-Robinson buffer solution with a pH of 6 and an oxidation potential of about +0.8 V. The calibration graph for the evaluation of B6 has a linear range from 1 to 100 μM, with a correlation coefficient of 0.9985 and a detection limit of 0.051 μM. The DyBO3-modified electrode can be used repeatedly, retaining more than 90% of the initial signal level after six cycles. The satisfactory selectivity offered a potential practical application of the chosen method for the monitoring of pyridoxine in artificially prepared biological fluids with acceptable recovery. In light of all the obtained results, this paper shows an important approach for the successful design of electrocatalysts with tuned architecture and opens new strategies for the development of materials for the needs of electrochemical (bio)sensing.

Ultrasensitive and highly selective electrochemical determination of mesalazine in pharmaceutical, biological and environmental samples with the use of Co-Mordenite/Mesoporous Carbon modified Glassy Carbon Electrode

In this paper, an ultrasensitive and highly selective analytical method for the voltammetric determination of the anti-inflammatory drug mesalazine (MES) at the Co-exchanged mordenite/mesoporous carbon modified glassy carbon electrode (Co-MOR/MC-GCE) is presented. The combination of unique properties of zeolite and mesoporous carbon, affirmed by conducting morphology and textural parameters studies, resulted in the fabrication of the unique platform sensing, which exhibited a significant enhancement effect of MES oxidation peak current. In the voltammetric determination of mesalazine by the means of differential pulse voltammetry (DPV), univariate optimization stage of the instrumental parameters and the pH value of the supporting electrolyte was performed. In 0.04 mol L−1 Britton-Robinson buffer solution (pH 2.0), the oxidation peak of MES at 0.41 V vs. Ag | AgCl | 3 M KCl reference electrode revealed a linear response in the range of 0.99 – 99.01 µg L−1 (6.47·10−9 – 6.47·10−7 mol L−1) with the limit of detection (LOD) equal to 0.27 µg L−1 (1.76·10−9 mol L−1). The developed protocol was successfully applied for the direct determination of mesalazine in pharmaceuticals, environmental waters, and biological fluids (human urine and serum) with recovery of 103.4 – 119.3%.

Electrochemical determination of budesonide: a common corticosteroid used to treat respiratory diseases such as COVID-19 and asthma

The outbreak of the COVID-19 pandemic has adversely affected the most important areas of the modern world. One of the challenges related to counteracting the effects of the pandemic it was necessary to develop methods for the quantitative determination of pharmaceuticals used in the treatment of patients suffering from this disease and its long-term effects. Budesonide (BUD) is a widely available and inexpensive corticosteroid used extensively not only among people suffering from COVID-19, but also asthma and other respiratory diseases. A significant increase in the consumption of drugs containing this component requires the development of new BUD determination methods, especially in real samples. This paper presents a new voltammetric method for BUD determination at renewable silver amalgam film electrode (Hg(Ag)FE). The electrochemical measurements were conduced in the supporting electrolyte containing 80% of methyl alcohol, 0.04 mol L−1 Britton–Robinson buffer (pH 3.0) and 20 mg mL−1 of NaClO4 under optimized differential pulse voltammetry (DPV) parameters. Detailed studies of the behaviour of the BUD on the surface of Hg(Ag)FE demonstrated the quasi-irreversible nature of the diffusion-controlled, two electrons and two protons reduction process. A calibration curve in the range from 1.0 to 290 µg mL−1 shows limit of detection and limit of quantification equal to 0.06 and 0.21 µg mL−1, respectively. The impact of numerous interferences over a wide range of concentrations on BUD signals was analysed and evaluated. The utility of the proposed method was verified by the quantitative analysis of BUD in two pharmaceutical products and the spiked water samples.Graphical abstract

A Green Voltammetric Determination of Molnupiravir Using a Disposable Screen-Printed Reduced Graphene Oxide Electrode: Application for Pharmaceutical Dosage and Biological Fluid Forms

A new green-validated and highly sensitive electrochemical method for the determination of molnupiravir (MOV) has been developed using cyclic voltammetry. The proposed analytical platform involves the use of a disposable laboratory-made screen-printed reduced graphene oxide 2.5% modified electrode (rGO-SPCE 2.5%) for the first time to measure MOV with high specificity. The surface morphology of the sensor was investigated by using a scanning electron microscope armed with an energy-dispersive X-ray probe. The fabricated sensor attained improved sensitivity when sodium dodecyl sulfate (SDS) surfactant (3 µM) was added to the supporting electrolyte solution of 0.04 M Britton–Robinson buffer at pH 2. The electrochemical activity of rGO-SPCE was examined in comparison with two different working electrodes in order to demonstrate that it was the most competitive sensor for MOV monitoring. The method was validated using differential pulse voltammetry according to ICH guidelines, resulting in good precision, accuracy, specificity, and robustness over a concentration range of 0.152–18.272 µM, with a detection limit of 0.048 µM. The stability investigation demonstrated that rGO-SPCE 2.5% can provide high-stability behavior towards the analyte throughout a six-week period under refrigeration. The fabricated rGO-SPCE 2.5% was successfully employed for the measurement of MOV in pharmaceutical capsules and human biofluids without the interference of endogenous matrix components as well as the commonly used excipient.

Preparation and Characterization of Patuletin-Loaded Chitosan Nanoparticles with Improved Selectivity and Safety Profiles for Anticancer Applications

Objective. This study aimed to investigate the preparation of patuletin-encapsulated chitosan nanoparticles (PT-CS-NPs) using the ionic gelation method, evaluate their potential as anticancer agents, and invent a new method of differential pulse voltammetric analysis for patuletin (PT). Methods. Computational studies were conducted to assess the affinity of PT for chitosan, confirming a promising interaction. PT-CS-NPs were synthesized based on the computational outputs, resulting in nanoparticles with an angular structure and an average size of 6.168 nm. The cytotoxicity of PT and PT-CS-NP was evaluated in breast and colon cancer cell lines, and selectivity indices were calculated to assess safety profiles. The electrochemical behavior of PT was also investigated using the Britton–Robinson buffer. Results. PT-CS-NP exhibited both potent cytotoxicity and a favorable safety profile, showing the most active and safest pattern of cytotoxicity among the tested compounds. The electrochemical oxidation of PT was observed at 0.531 V vs. Ag/AgCl at pH 4.0.0. The concentration of PT showed a linear relationship with the corresponding peak current over the range of 10.0 x 10 − 9 : 10.0 x 10 − 5 M M, with a minimum limit of detection of 3.4 × 10(−9)M. The proposed method successfully measured PT, with a relative standard deviation below 2%. Conclusion. The preparation of PT-CS-NP via the ionic gelation method resulted in angular nanoparticles with a promising anticancer activity and safety profiles. The electrochemical behavior of PT was characterized, and a reliable method for PT quantification was established.

Caftaric acid oxidation in the presence of cell signaling regulator glutathione: Electrochemical and chromatographic analyses

New antioxidant materials in biomedical applications are an exciting research topic. However, the lack of understanding of the products/intermediates formed and the interaction between nucleophiles and these antioxidants will prevent commercial or industrial applications. To overcome this obstacle, chromatographic techniques, mass spectroscopy, and electrochemical analyses were combined to study the mechanism and products of the expected reaction between antioxidants and nucleophiles. Grape juice contains phenolic compounds such as 2-S-glutathionylcaftaric acid, which is formed as a result of oxidative action. Through UPLC and voltammetric analysis of caftaric acid (CFT) and its quinone with glutathione (GSH), the oxidation and subsequent reactions were monitored. Electrochemical techniques such as cyclic voltammetry (CV) and chronoamperometry (CA) have been used to investigate the electrochemical oxidation characteristics of the investigated CFT in a Britton-Robinson (B-R) buffer electrolyte. As a result of the analysis of ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) results, the oxidation products were identified to suggest the optimal mechanism for the oxidation of CFTs both in the presence and absence of GSH. A reversible oxidation process is observed at pH 1.8 for CFT without glutathione (GSH) at E1/2 = 0.52 V against Ag/AgCl 3.0 M KCl) using cyclic voltammetry. During this electrochemical process, two electrons in the CFT molecule were oxidized along with two protons, forming o-quinone. In the presence of GSH, the formed quinone either reacts with glutathione to form mono- and bi-glutathione CFT conjugates or is reduced by GSH to its original state. As a result of the UPLC-MS analysis, the oxidation products of CFT were identified, and the reaction pathways were proposed.

Valence-Engineered Oxidase-Mimicking Nanozyme with Specificity for Aromatic Amine Oxidation and Identification.

Oxidase-mimicking nanozymes with specificity for catalyzing oxidation of aromatic amines are of great significance for recognition of aromatic amines but rarely reported. Herein, Cu-A nanozyme (synthesized with Cu2+ as a node and adenine as a linker) could specifically catalyze oxidation of o-phenylenediamine (OPD) in Britton-Robinson buffer solution. Such a specific catalytic performance was also corroborated with other aromatic amines, such as p-phenylenediamine (PPD), 1,5-naphthalene diamine (1,5-NDA), 1,8-naphthalene diamine (1,8-NDA), and 2-aminoanthracene (2-AA). Moreover, the presence of salts (1 mM NaNO2, NaHCO3, NH4Cl, KCl, NaCl, NaBr, and NaI) greatly mediated the catalytic activity with the order of NaNO2 < blank ≈ NaHCO3 < NH4Cl ≈ KCl ≈ NaCl < NaBr < NaI, which was due to anions sequentially increasing interfacial Cu+ content via anionic redox reaction, while the effect of cations was negligible. With the increased Cu+ content, Km decreased and Vmax increased, indicating valence-engineered catalytic activity. Based on high specificity and satisfactory activity, a colorimetric sensor array with NaCl, NaBr, and NaI as sensing channels was constructed to identify five representative aromatic amines (OPD, PPD, 1,5-NDA, 1,8-NDA, and 2-AA) as low as 50 μM, quantitatively analyze single aromatic amine (with OPD and PPD as model analysts), and even identify 20 unknown samples with an accuracy of 100%. In addition, the performance was further validated through accurately recognizing various concentration ratios of binary, ternary, quaternary, and quinary mixtures. Finally, the practical applications were demonstrated by successfully discriminating five aromatic amines in tap, river, sewage, and sea water, providing a simple and feasible assay for large-scale scanning aromatic amine levels in environmental water samples.

Electrochemical testosterone biosensor based on pencil graphite electrode electrodeposited with copper oxide nanoparticles

Accurately monitoring the blood levels of testosterone (TST) in a sensitive, simple, and rapid manner is of paramount importance for the diagnosis and treatment of various medical conditions, as well as for controlling pharmaceutical quality and facilitating doping detection. TST, the primary male sex hormone, plays a crucial role in facilitating human physical performance, protein synthesis, and the development of muscle mass. Consequently, TST and its analogues are frequently abused by athletes as performance-enhancing steroid in order to increase muscle mass and enhance their performance. The use of such steroids is strictly prohibited to guarantee fair play. In this study, we employed a pencil graphite electrode that was electrochemically modified with CuO nanoparticles (CuONPs) for determination of TST. The electrode response was significantly enhanced by approximately fourfold compared to the unmodified pencil graphite electrode (PGE) when electrodeposition CuONPs onto PGE surface was performed at a potential of −0.6 V for 200 s. The success of modification was confirmed through morphological analysis using scanning electron microscopy and energy-dispersive x-ray spectroscopy. Using square wave adsorptive stripping voltammetry analysis in Britton–Robinson buffer at pH 6.0, we demonstrated that the proposed sensor exhibited sensitivity to detect TST within a linear range of 5–200 nM. The detection limit of sensor was calculated 4.6 nM (1.32 ng ml−1). The sensor platform developed for the accurate, sensitive, and specific determination of TST holds tremendous potential for the development of point-of-care devices and their integration into lab-on-a-chip research.

Effect of Magnesium Chloride in Supporting Electrolyte for Enhancing Sensitive and Selective Electrochemical Sensor: An Approach for Anti-Rheumatic Sulfasalazine Detection

In this work, an electroanalytical evaluation for voltammetric sensing of the anti-rheumatic sulfasalazine (SSZ) at an unmodified screen-printed graphene electrode (SPGE) is demonstrated. By using the differential pulse (DPV) technique, the SSZ produced a well-defined peak of around −0.3 V (vs Ag AgCl−1) in Britton-Robinson (BR) buffer pH 4. Supporting electrolytes, pH, and salts all significantly impact SSZ reduction. Therefore, their impact on the working solutions was assessed. We discovered that using a mixture of Britton–Robinson (BR) buffer with pH 4 and MgCl2 as a supporting electrolyte can enhance SSZ sensitivity by approximately 1.7 times while simultaneously increasing detection selectivity. Under optimal conditions, the proposed assay demonstrated the ultrasensitive determination of SSZ with a broad linear detection range from 0.01 to 100 μM and a low detection limit of 4.7 nM (S/N = 3). To demonstrate the impact of the proposed method, the sensor has been successfully applied for the quantitative determination of SSZ in pharmaceutical, urine, and artificial serum sample. Therefore, this approach could offer simplicity, and rapidity, and serve as an alternative to the SSZ detection in practical applications.

Advanced electrochemical platform for simple and rapid quantification of tannic acid in beverages using batch injection analysis with amperometric detection

In this work, an advanced electrochemical platform was developed for the simple, rapid and sensitive determination of the polyphenolic compound tannic acid in various beverages using the combination of batch injection analysis with amperometric detection on a screen-printed carbon electrode. Several experimental parameters (pH of supporting electrolyte, detection potential, dispensing rate, injected volume, stirring) were consistently evaluated. The most favorable analytical performance in terms of sensitivity, selectivity, repeatability and sampling frequency was obtained in Britton-Robinson buffer pH 5.0 at a detection potential of +0.6 V vs. Ag/AgCl, a dispensing rate of 204 µL/s and an injected volume of 80 µL under stirring condition (1500 r.p.m.). The presented platform has advantages for routine analysis including portable and small-scale experimental setup, low sample consumption (∼100 µL), simple sample preparation (dilution in supporting electrolyte), high sampling frequency (180 injections per hour), low limit of detection (80 nM) and suitable precision (RSD = 4.2% for 10 μM tannic acid, n = 20). The applicability of the method was verified by analyzing several beverage samples (tea, wine) in spike-recovery assay with the recovery values for tannic acid ranging from 94 to 101 %.

Graphene and gold nanoparticle-based bionanocomposite for the voltammetric determination of bisphenol A in (micro)plastics

The monitoring of endocrine disruptors in the environment is one of the main strategies in the investigation of potential risks associated with exposure to these chemicals. Bisphenol A is one of the most prevalent endocrine-disrupting compounds and is prone to leaching out from polycarbonate plastic in both freshwater and marine environments. Additionally, microplastics also can leach out bisphenol A during their fragmentation in the water environment. In the quest for a highly sensitive sensor to determine bisphenol A in different matrices, an innovative bionanocomposite material has been achieved. This material is composed of gold nanoparticles and graphene, and was synthesized using a green approach that utilized guava (Psidium guajava) extract for reduction, stabilization, and dispersion purposes. Transmission electron microscopy images revealed well-spread gold nanoparticles with an average diameter of 31 nm on laminated graphene sheets in the composite material. An electrochemical sensor was developed by depositing the bionanocomposite onto a glassy carbon surface, which displayed remarkable responsiveness towards bisphenol A. Experimental conditions such as the amount of graphene, extract: water ratio of bionanocomposite and pH of the supporting electrolyte were optimized to improve the electrochemical performance. The modified electrode displayed a marked improvement in current responses for the oxidation of bisphenol A as compared to the uncovered glassy carbon electrode. A calibration plot was established for bisphenol A in 0.1 mol L−1 Britton-Robinson buffer (pH 4.0), and the detection limit was determined to equal to 15.0 nmol L−1. Recovery data from 92 to 109% were obtained in (micro)plastics samples using the electrochemical sensor and were compared with UV–vis spectrometry, demonstrating its successful application with accurate responses.

Green micellar spectrofluorimetric determination of α-mangostin found in herbal products as antioxidant and other biological activities beneficial to human health.

Pharmaceutical product quality control (QC) needs quick, sensitive and economical procedures to deliver high throughput at low cost, which is the key factor considered by such economic facilities. To lessen the risky effects of research laboratories, researchers must take into account the ecological impacts. α-Mangostin (MAG) exhibit anti-inflammatory, antioxidant, anticancer, anti-allergic, antibacterial, antifungal, antiviral and antimalarial activities. Based on the spectrofluorimetric approach, a novel straightforward, sensitive and environmentally friendly method for MAG determination was developed and validated. Many variables were investigated to improve MAG native fluorescence, including solvent type, buffers, pH and additional surfactants. The best MAG fluorescence sensitivity was found in Britton-Robinson buffer (pH4) at 450 nm after irradiation at 350 nm in the concentration range of 5-50 ng ml-1 . The technique was successfully used to determine the presence of MAG in both its approved dose forms and in samples of spiked human plasma, as per FDA standards for validation. According to their evaluation on two recent greenness criteria (GAPI [Green Analytical Procedure Index] and AGREE [Analytical GREEnness]), the suggested approach has been shown to be environmentally beneficial because it normally uses biodegradable chemicals in solvent-free aqueous phases.

Sensitive and selective voltammetric method for determination of quinoline alkaloid, quinine in soft drinks and urine by applying a boron-doped diamond electrode

In this paper, for the first time, the method of determination of the alkaloid of quinoline derivation, quinine (QN), was developed. A miniatured planar electrochemical cell with a working electrode, a boron-doped diamond electrode (BDDE), was used. QN is easily oxidized in a strongly acidic environment – 2 M HClO4 at a potential of Epa = +1.42 V, and in an alkaline environment.Epa = +0.94 – +1.18 V, depending on the pH of the medium at the surface of BDDE. Also, QN is reduced within wide pH ranges at the background of the Britton–Robinson buffer (Epc = −1.11 – −1.51 V). This enables the simultaneous determination of QN by anodic and cathodic currents. The conditions for the determination of QN were optimized. Calibration curves under optimal conditions were obtained using differential pulse voltammetry (DPV) and square-wave voltammetry (SWV). The limit of detection of QN according to the cathodic peak is at the level of 10−7M. According to the peak of QN oxidation, the sensitivity is worse, and the limit of detection of QN is at the level of 10−6M. The developed method was tested in the analysis of soft drinks. The results were compared with those of high performance liquid chromatography. The obtained results were statistically processed using the relative errors and Student t-test. Uric acid, nicotine, and caffeine, which can often be present in biological fluids, do not affect the oxidation and reduction of QN on BDDE. Various methods of urine sample preparation for voltammetric analysis were investigated. The proposed method can determine QN in urine at the level of 1.0 μg/ml of urine.

Two green spectrofluorimetric methods for the assay of atomoxetine hydrochloride in pure form and commercial capsules with application to content uniformity testing.

Atomoxetine hydrochloride (ATX) is a potent and non-stimulant drug which was approved for the treatment of attention-deficit hyperactivity disorder. Owing to its importance, two green, simple and validated spectrofluorimetric methods were developed for its sensitive assay in pure and capsule forms. The first method (Method I) relied on measuring the enhanced fluorescence of ATX by the use of sodium dodecyl sulfate in alkaline medium at λ ex 227 nm/λ em 298 nm. The second method (Method II) involved complex formation of ATX with Erythrosine B (EB) in aqueous acidic solution resulting in quantitative quenching of the EB naive fluorescence. This complex was formed in the presence of Britton-Robinson buffer (pH 4.0). The difference in fluorescence intensity was measured at λ ex 527/λ em550 nm. The calibration curves were linear through the ranges of 0.2-2.0 µg ml-1 for Method I, 0.2-4.0 µg ml-1 for Method II with good correlation coefficient (r = 0.9998) for both methods. The suggested methods were perfectly applied for determination of ATX in its commercial capsules and content uniformity test. The greenness of the proposed methods was confirmed by three different assessment tools and it was found that both methods were green, eco-friendly and environmentally safe.

Halochromic Silk Fabric as a Reversible pH-Sensor Based on a Novel 2-Aminoimidazole Azo Dye

Textiles are important components for the development of lightweight and flexible displays useful in smart materials. In particular, halochromic textiles are fibrous materials with a color-changing ability triggered by pH variations mainly based on pH-sensitive dye molecules. Recently, a novel class of 2-aminoimidazole azo dyes was developed with distinct substituent patterns. In this work, silk fabric was functionalized through exhaustion for the first time with one of these dyes (AzoIz.Pip). The halochromic properties of the dye were assessed in an aqueous solution and after silk functionalization. The solutions and the fabrics were thoroughly analyzed by ultraviolet-visible (UV-vis) spectra, color strength (K/S), color difference (∆E), CIE L*a*b* coordinates, and the ultraviolet protection factor (UPF). The dyeing process was optimized, and the halochromic performance (and reversibility) was assessed in universal Britton-Robinson buffers (ranging from pH 3 to 12) and artificial body fluids (acid and alkaline perspiration, and wound exudate). AzoIz.Pip showed vibrant colors and attractive halochromic properties with a hypsochromic shift from blue (557 nm) to magenta (536 nm) in aqueous buffered solutions. Similarly, the functionalized silk showed a shift in wavelength of the maximum K/S value from 590 nm to 560 nm when pH increases. The silk fabric showed a high affinity to AzoIz.Pip, and promoted additional color stabilization of the dye, avoiding color loss as observed when the dye is in solution at alkaline pH after 24 h. The color reversibility was effective up to the fourth cycle and the fastness tests denoted suitable results, except washing fastness. The cytotoxicity of the silk fabric extracts was assessed, depicting reduced viability of HaCaT cells to <70% only when the dye concentration in the fabric is higher or equal to 64 μg·mL-1. Nevertheless, lower concentrations were also very effective for the halochromic performance in silk. These materials can thus be a helpful tool for developing sensors in several sectors such as biomedicine, packaging, filtration, agriculture, protective apparel, sports, camouflage, architecture, and design.

Carbon Fiber Paper Sensor for Determination of Trimethoprim Antibiotic in Fish Samples.

The increase in anthropogenic pollution raises serious concerns regarding contamination of water bodies and aquatic species with potential implications on human health. Pharmaceutical compounds are a type of contaminants of emerging concern that are increasingly consumed and, thus, being frequently found in the aquatic environment. In this sense, an electrochemical sensor based on an unmodified and untreated carbon fiber paper (CPS-carbon paper sensor) was simply employed for the analysis of trimethoprim antibiotic in fish samples. First, the analytical conditions were thoroughly optimized in order for the CPS to achieve maximum performance in trimethoprim determination. Therefore, an electrolyte (0.1 M Britton-Robinson buffer) pH of 7 was selected and for square wave voltammetry parameters, optimum values of amplitude, frequency and step potential corresponded to 0.02 V, 50 Hz, and 0.015 V, respectively, whereas the deposition of analyte occurred at +0.7 V for 60 s. In these optimum conditions, the obtained liner range (0.05 to 2 µM), sensitivity (48.8 µA µM-1 cm-2), and LOD (0.065 µM) competes favorably with the commonly used GCE-based sensors or BDD electrodes that employ nanostructuration or are more expensive. The CPS was then applied for trimethoprim determination in fish samples after employing a solid phase extraction procedure based on QuEChERS salts, resulting in recoveries of 105.9 ± 1.8% by the standard addition method.

Pulsed-post column derivatization coupled to green liquid chromatography for the determination of glutathione and cysteine based on thioacrylates formation

In the present work, we developed a method for the determination of thiols (cysteine and glutathione) in yeast samples under the new concept of Pulsed-post column derivatization (Pulsed-PCD). For the chromatographic separation of the analytes, 100% aqueous mobile phase was used and the eluted compounds reacted on-line with the injected pulses (100 μL) of the derivatizing reagent (ethyl propiolate + Britton-Robinson buffer). Spectrophotometric detection of the derivatives was carried out at 285 nm. The Pulsed-PCD configuration, the selection of the analytical column and the pulsed-PCD reaction conditions were investigated. The method was validated for the determination of endogenous content of the analytes in dry and fresh yeasts, with LODs of 3.0 μmol L−1. The percent recovery ranged between 85.2 and 114.4% in all cases and the results were compared with a corroborative method based on classical PCD. The analytical greenness of the proposed method was evaluated using two tools; Analytical Eco-Scale and Green Analytical Procedure Index (GAPI). The greenness score of the HPLC-Pulsed-PCD method (score = 77) was compared with that of the corroborative HILIC-PCD method (score = 71) and was found to be greener in terms of the amount of chemicals used and the produced wastes.

A novel electrochemical acetaminophen sensor based on multiwalled carbon nanotube and poly(neutral red) modified electrodes with electropolymerization in ternary deep eutectic solvents

A new electrochemical sensor based on a neutral red (NR) and multiwalled carbon nanotubes (CNT) modified glassy carbon electrode (GCE) with NR electropolymerized in ternary deep eutectic solvents (DES), has been developed. Cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy were used to characterize the performance of the sensor. Differential pulse voltammetry was utilized to evaluate the analytical performance of acetaminophen (APAP) oxidation on the modified electrode (PNR/CNT/GCE) in Britton-Robinson buffer aqueous solution. The combined use of PNR prepared by electropolymerization in novel green DES on CNT led to a large electroactive surface area and a synergistic effect attributed to π–π electronic interactions and resulted in improved performance towards APAP detection, with a high sensitivity (56.4 µA µM−1 cm−2) in the range 2.0–70 µM and a low limit of detection (0.015 µM). The constructed sensor displayed outstanding selectivity to detect APAP in the presence of dopamine, and good repeatability, reproducibility and stability. The sensor was successfully applied to the determination of APAP in pharmaceutical samples, with good recoveries.

A disposable electrochemical sensor based on single-walled carbon nanotubes for the determination of anticancer drug dasatinib

Dasatinib is an anticancer drug that treats acute lymphoblastic leukemia, chronic myelogenous leukemia, and prostate cancer with several side effects. In this research, we suggest nanoparticle-modified screen-printed electrodes (SPCEs) as disposable electrochemical sensors for fast quantification of dasatinib in pharmaceutical formulations. Carbon nanotubes, single-walled carbon nanotubes (SWCNT), graphene, and graphene oxide-modified SPCEs were characterized by scanning electron microscopy. The study also recommends SWCNT-modified SPCEs as the best-performing electrode for determining dasatinib, demonstrating an excellent boosting effect on the oxidation response of dasatinib. This was accomplished using the square-wave voltammetry method. After optimization of the pH condition, pH 5.0 Britton–Robinson buffer, SWCNT-modified SPCEs demonstrated 94% recovery with optimum electro-oxidation activity. The oxidation currents exhibited linear relation with dasatinib concentration in the 0.1–100 µM. Based on the results, a limit of detection of 0.06 µM was obtained in the standard solution. The SWCNT-modified SPCEs have been applied to analyze dasatinib in pharmaceutical tablet samples. The demonstrated performance beats all comparable standard analytical tools and presumably may be used for general drug quantitation in pharmaceutical tablets.Graphical abstract