Acetate Buffer Solution Research Articles

Volumetric, Viscometric and Spectroscopic Properties of Glycylglycine in Citrate and Acetate Buffer Solutions at Different Temperatures

Volumetric, Viscometric and Spectroscopic Properties of Glycylglycine in Citrate and Acetate Buffer Solutions at Different Temperatures

Determination of ten aminoglycoside residues in eggs by mixed-mode ion exchange liquid chromatography-tandem mass spectrometry

该研究系统地优化了样品前处理过程及仪器分析中影响氨基糖苷残留分析准确度与灵敏度的各主要因素,建立了鸡蛋中10种氨基糖苷类药物(链霉素、双氢链霉素、潮霉素B、卡那霉素、阿米卡星、妥布霉素、安普霉素、大观霉素、新霉素、庆大霉素)残留量的混合型离子交换液相色谱-串联质谱分析方法。样品经10 mmol/L乙酸铵缓冲溶液(含0.4 mmol/L EDTA和50 g/L三氯乙酸)超声提取,调节pH至6~7后,经PRiME HLB固相萃取柱富集净化,采用SIELC Obelisc R色谱柱分离,以乙腈和1.0%(v/v)甲酸水溶液(含1 mmol/L甲酸铵)为流动相进行梯度洗脱,在正离子、多反应监测模式下经串联质谱仪测定,外标法定量。该方法在5~200 μg/L质量浓度范围内线性关系良好,相关系数(r2)均大于0.99;方法的检出限(LOD, S/N≥3)为2~5 μg/kg,定量限(LOQ, S/N≥10)为5~10 μg/kg。在空白鸡蛋中进行LOQ、20 μg/kg、100 μg/kg 3个水平的加标回收实验,方法的平均回收率(n=6)为68.1%~111.3%,相对标准偏差为1.2%~12.3%。利用该方法对市售的20批次鸡蛋样品进行测定,均未检出目标物。本方法简单、灵敏、准确,可实现鸡蛋中10种氨基糖苷类药物残留的批量检测。

Multi-residue determination of twenty aminoglycoside antibiotics in various food matrices by dispersive solid phase extraction and liquid chromatography-tandem mass spectrometry

An analytical method has been developed for the simultaneous determination of twenty aminoglycosides (AGs) in meat, milk, and egg using liquid chromatography-tandem mass spectrometry. The target analytes were separated on a reverse-phase C18 column and eluted with acetonitrile containing the ion-pairing reagent (heptafluorobutyric acid). For sample preparation, we used ammonium acetate buffer solution and dispersive solid-phase cleanup (C18). Linearity was obtained >0.98 (r2). The trueness (average recoveries) was between 70 and 118%. The precision (coefficient of variation) was in the range of 1–27%. The proposed method provides reliable screening, quantification, and identification of twenty AGs residues in various food matrices. The method was applied to analyze real samples collected from local market, demonstrating that method is robust and useful for determining AGs residues.

Expired streptomycin as corrosion inhibitor for carbon steel in acetic acid - sodium acetate buffer solution

Corrosion inhibition of carbon steel in buffer acid solutions by expired streptomycin was studied by weight loss method, linear polarization, electrochemical impedance spectroscopy, as well as scanning electron microscopy. It was found that streptomycin reduces the metal corrosion rate, and the inhibition efficiency increases proportionally with the drug content. A high efficiency has been obtained for 10–3 M amount of inhibitor. Tafel polarization results indicate that the drug is active especially on the cathodic side and less on the anodic dissolution of iron reaction, acting as a mixed type corrosion inhibitor. The double layer capacitance of the metal - buffer solution interface, polarization resistance and film formation on the carbon steel surface have been emphasized by electrochemical impedance measurements. The scanning electron micrographs of the carbon steel samples in blank solutions have revealed a severe corrosion on the samples surface, while in the presence of the expired drug, the surface has remained almost unaffected. Electrochemical behavior of streptomycin has been also investigated by cyclic voltammetry.

Thermophysical studies of protonated and deprotonated glycine in aqueous sodium acetate buffer solutions at different temperatures

Interactions of glycine in water and in (0.10, 0.50 and 1.00) aqueous sodium acetate buffer solutions of pH (1.00 and 12.40) have been investigated at different temperatures, T/K = (298.15-318.15). Densities, and viscosities, of glycine in water and in aqueous sodium acetate buffer solutions have been measured. The obtained density data have been used to calculate apparent molar volume, , limiting partial molar volume, , limiting partial molar volumes of transfer, . Viscosity B-coefficient, viscosity B-coefficient of transfer, , Activation free energies per mole of the solute, and solvent, have been calculated from viscosity data. Further, second order derivative of partial molar expansion coefficient and dependence of coefficients on temperature is useful in measuring the structure making and breaking behavior of solute in these systems. Pair and triplet interaction coefficients for both the properties were also calculated. Thus, the results obtained from volumetric and viscometric studies are of considerable importance to identify different type of interactions (i.e. H-bonding, van der Waal’s interactions)in these systems.

Highly Sensitive and Stable Determination of As(III) under Near-Neutral Conditions: Benefit from the Synergetic Catalysis of Pt Single Atoms and Active S Atoms over Pt1/MoS2.

Designing new catalysts with high activity and stability is crucial for the effective analysis of environmental pollutants under mild conditions. Here, we developed a superior catalyst of Pt single atoms anchored on MoS2 (Pt1/MoS2) to catalyze the determination of As(III). A detection sensitivity of 3.31 μA ppb-1 was obtained in acetate buffer solution at pH 6.0, which is the highest compared with those obtained by other Pt-based nanomaterials currently reported. Pt1/MoS2 exhibited excellent electrochemical stability during the detection process of As(III), even in the coexistence of Cu(II), Pb(II), and Hg(II). X-ray absorption fine structure spectroscopy and theoretical calculations revealed that Pt single atoms were stably fixed by four S atoms and activated the adjacent S atoms. Then, Pt and S atoms synergistically interacted with O and As atoms, respectively, and transferred some electrons to H3AsO3, which change the rate-determining step of H3AsO3 reduction and reduce reaction energy barriers, thereby promoting rapid and efficient accumulation for As(0). Compared with Pt nanoparticles, the weaker interaction between arsenic species and Pt1/MoS2 enabled the effortless regeneration and cyclic utilization of active centers, which is more favorable for the oxidation of As(0). This work provides inspiration for developing highly efficient sensing platforms from the perspective of atomic-level catalysis and affords references to explore the detection mechanism of such contaminants.

Simple laser-induced graphene fiber electrode fabrication for high-performance heavy-metal sensing

In this paper, we describe the simple fabrication and characterization of a high-performing heavy metal sensor by using laser-induced graphene fiber (LIGF) electrodes for simultaneous detection of cadmium (Cd2+) and lead (Pb2+) ions. Both LIG and LIGF were grown via extremely simple and fast method, compared to conventional graphene synthesis, on a commercial polyimide film by irradiating CO2 infrared laser with the appropriate energy level (46 J/cm2 in this work). Fabricated LIG and LIGF were analyzed by FE-SEM and Raman spectroscopy, which showed that the LIGF structure was composed of randomly stacked three-dimensional porous graphene layers and fibers. On the surface of the LIGF working electrode, bismuth was electro-deposited in-situ for the electrochemical detection of heavy metal ions. The fabricated LIGF electrode heavy metal sensor was used for the simultaneous detection of Cd and Pb ions in 0.1 M acetate buffer solution at pH 4.5 by square wave anodic stripping voltammetry. The fabricated LIGF-based heavy-metal sensor showed high sensitivity (0.19 and 0.20 μA μg−1 L for Cd and Pb ions), broad linear detection ranges (1.0 to 140.0 μg/L for Cd and Pb ions), and low detection limits (0.4 μg/L (S/N = 3) for both Cd and Pb ions), showing great promise in high-performance heavy metal detection applications that require fast and simple manufacturing practices.

Electrochemically Activated Screen-Printed Carbon Electrode for Determination of Ibuprofen

In this study, we present a simple, sensitive and selective analytical procedure for the ibuprofen (IBP) analysis using the commercially available screen-printed carbon electrode electrochemically activated (aSPCE) by cyclic voltammetry in 0.1 M NaOH. The quantitative determinations of IBP were carried out in 0.25 M acetate buffer solution of pH 4.5 ± 0.1 using the differential-pulse voltammetry (DPV). Different experimental parameters for DPV analysis were optimized, including pH and concentration of supporting electrolyte, amplitude (ΔEA), scan rate (ν) and modulation time (tm). The linear ranges of calibration curve were from 0.50–20.0 and 20.0–500.0 µM. The detection and quantification limits were estimated to be 0.059 and 0.20 µM. The aSPCE displayed satisfactory repeatability, reproducibility, and selectivity. Furthermore, the DPV procedure with the use of aSPCE was used to determination of IBP in pharmaceutical formulations. The results achieved by DPV show satisfactory agreement with those obtained by manufacturers (the relative errors are in the range of 3.1–4.7%).

Fabrication of a novel polyaniline/green‐synthesized, silver‐nanoparticle‐modified carbon paste electrode for electrochemical sensing of lead ions

AbstractGreen bioreduction silver nanoparticles (AgNPs) were fabricated from dry Artemisia leaf extracts and used as a modified layer of an AgNP–polyaniline (PANI)–carbon paste electrode (CPE). PANI was synthesized using interfacial polymerization, and the fabricated PANI was mixed with a CPE. PANI was characterized using scanning electron microscopy (SEM), whereas AgNPs were characterized using transmission electron microscopy (TEM), energy‐dispersive X‐ray (EDX) analysis, ultraviolet–visible (UV–Vis), Fourier‐transform infrared (FTIR), and polydispersity index (PDI) measurements. The fabricated electrode was used for the electrochemical detection of Pb2+ ions in acetate buffer solution at pH 5.5 using square‐wave voltammetry (SWV). The AgNP/PANI‐CPE electrode provided a linear response to Pb2+ ions in the concentration range of 0.1–120 μM with a detection limit of 0.04 μM. The AgNP/PANI‐CPE electrode exhibited excellent selectivity, reproducibility, and stability in addition to providing good recovery percentages in waste and tap water samples.

The effect of D-(+)-glucosamine, N-acetyl-D-glucosamine and tetraethylene glycol on the stability of oxytocin in aqueous solution.

The aim of the present study was to identify the effect of D-(+)-glucosamine, N-acetyl-D-glucosamine, tetraethyleneglycol, and the mixture of these additives on the stability of oxytocin in phosphate and acetate buffer solutions, at pH 4.5. Our findings demonstrate that tetraethyleneglycol has a destabilizing effect on oxytocin in both phosphate buffer and acetate buffer. D-(+)-Glucosamine hydrochloride had small to negligible effect at low concentrations, yielding a slight improvement lower concentrations of the additive in the presence of the buffers used, but at higher concentrations it increased the rate of degradation. N-Acetyl-D-glucosamine showed a possibly slight improvement to the stability of oxytocin. It is hypothesized that the different effect of N-acetyl-D-glucosamine compared to D-(+)-glucosamine is a consequence of the free amine group in D-(+)-glucosamine promoting a faster degradation, while the amino group is acetylated in N-acetyl-D-glucosamine and therefore no longer reactive in the same way. While it remains unclear why tetraethyleneglycol has a destabilizing effect on oxytocin, the D-(+)-glucosamine results aid in deepening our understanding of the degradation mechanism of oxytocin.

Hemoglobin-Modified Core–Shell Fe3O4@Au Nanostructures for the Electrochemical Detection of Acrylamid

In this study, electrochemical detection of acrylamide using hemoglobin (Hb)-modified core–shell Fe3O4@Au nanostructures was conducted. Fe3O4 nanoparticles (~4.9 nm) and core–shell Fe3O4@Au (5.0–6.4 nm) nanostructures were successfully synthesized by the thermal decomposition method. Electrochemical investigation revealed that the optimum amount of Hb of 2 mg/mL could be immobilized in 0.1 M acetate buffer solution (pH = 6). Moreover, the detection of acrylamide using Fe3O4@Au/Hb was evaluated by the cyclic voltammetry technique. A linear calibration curve (R2 = 0.98) in the concentration range of 0.1 to 1.0 µM could be achieved with an estimated limit of detection, limit of quantification, and sensitivity of 0.136 µM, 0.453 µM, and 0.4411 µA/µM, respectively. Furthermore, the developed biosensor exhibited high selectivity in the presence of ascorbic acid, melamine, and caffeine. The developed biosensor was applied to the detection of acrylamide in coffee samples and validated using the standard high-performance liquid chromatography (HPLC) method. The concentration of acrylamide in coffee samples was determined to be 37.450 and 35.377 ppm using electrochemical measurement and HPLC, respectively.

Sensitive electrochemical determination of Cefpirome in human urine using differential pulse voltammetry

Cefpirome, which is a fourth-generation cephalosporin, was analyzed for the first time at a glassy carbon electrode using differential pulse voltammetry in this novel method. Different experimental conditions were optimized, such as pH and electrolyte type, to achieve a high peak current. Under the optimum conditions, the oxidation of cefpirome exhibited diffusion-controlled process depending on pH. Cefpirome was electrochemically determined at the linear range between 2-200 µM, and the detection limit was found as 0.167 µM in pH 4.7 acetate buffer solution. Analysis results showed that the proposed electrochemical method could be used for the determination of cefpirome in human urine samples. A linear relationship has been obtained in the concentration range of 2-10 µM. At the same time, the detection limit was found as 0.101 µM for cefpirome in human urine. Moreover, to check the selectivity of the proposed method, the effect of some interference species, including ascorbic acid, uric acid, dopamine, glucose, 〖"Na" 〗^"+" , "K" ^"+" , 〖"Ca" 〗^"+2" , 〖"NO" 〗_"3" ^"-" , have also been investigated. As a result, a simple, sensitive, reproducible, no time-consuming, and more environmentally friendly method was developed when compared to the literature studies.

Improvement of potassium species dispersed on hierarchical zeolite NaY by using combined methods between ultrasound and microwave-assisted impregnation as catalysts for transesterification of refined Jatropha seed oil

Refined Jatropha seed oil, non-edible vegetable oil is an interesting source for biodiesel production because it has low commercial value. Thus, this work aimed to develop a novel method, combined techniques between ultrasound and microwave-assisted impregnation ((UA-IP and MA-IP) for potassium (K) loaded on hierarchical NaY zeolite synthesized from rice husk silica as catalysts for transesterification of Jatropha seed oil. Hierarchical NaY zeolite was impregnated with potassium acetate in an acetic acid buffer solution with various contents (xK/NaY, where X = 6, 8, 10, and 12 wt%) by UA-IP and MA-IP. The best catalyst from the novel method was further compared to the control method, prepared by only UA-IP. Results from XRD and N2-sorption indicated the remaining NaY structure in all samples after calcination. The total surface area determined by BET method decreased with the K loading but basicity increased with K loading suggested by CO2 -TPD. The active species was mainly K2CO3 confirmed by FTIR. When tested in transesterification at a temperature of 60 °C and 3 h with methanol: oil molar ratio of 16:1, the biodiesel yield improved with the K loading and the highest biodiesel yield of 97 ± 1.4% was obtained by 12K/NaY. The 12K/NaY gave a higher yield than 12K/NaY-control (97 ± 1.4% vs 90.7 ± 1.1%), providing the high reusability of five cycles with the biodiesel yield of 88.2 ± 1.3%.

High Performance Liquid Chromatography–Tandem Mass Spectrometry Method for Correlating the Metabolic Changes of Lactate, Pyruvate and L-Glutamine with Induced Tamoxifen Resistant MCF-7 Cell Line Potential Molecular Changes

Breast cancer is one of the most prevalent cancers worldwide usually treated with Tamoxifen. Tamoxifen resistance development is the most challenging issue in an initially responsive breast tumor, and mechanisms of resistance are still under investigation. The objective of this study is to develop and validate a selective, sensitive, and simultaneous high performance liquid chromatography–tandem mass spectrometry method to explore the changes in substrates and metabolites in supernatant media of developed Tamoxifen resistance MCF-7 cells. We focus on the determination of lactate, pyruvate, and L-glutamine which enables the tracking of changes in metabolic pathways as a result of the resistance process. Chromatographic separation was achieved within 3.5 min. using a HILIC column (4.6 × 100 mm, 3.5 µm particle size) and mobile phase of 0.05 M acetic acid–ammonium acetate buffer solution pH 3.0: Acetonitrile (40:60 v/v). The linear range was 0.11–2.25, 0.012–0.227, and 0.02–0.20 mM for lactate, pyruvate, and L-glutamine, respectively. Within- and between-run accuracy was in the range 98.94-105.50% with precision (CV, %) of ≤0.86%. The results revealed a significant increase in both lactate and pyruvate production after acquiring the resistant. An increase in L-glutamine levels was also observed and could be attributed to its over production or decline in its consumption. Therefore, further tracking of genes responsible of lactate, pyruvate, and glutamine metabolic pathways should be performed in parallel to provide in-depth explanation of resistance mechanism.

Development and validation of a new stability indicating RP-UFLC method for the estimation of Bosentan

A new stability-indicating RP-UFLC method has been developed for the estimation of Bosentan in pharmaceutical dosage forms and the method was validated. Bosentan is used to lower the high blood pressure in lungs (pulmonary arterial hypertension). Bosentan acts by blocking the actions of endothelin -1and thereby lowers the blood pressure. Mobile phase mixture consisting of sodium acetate (pH 5.0) buffer solution and acetonitrile (50: 50 v/v) with flow rate 0.7 mL/min were the optimized chromatographic conditions (Detection wavelength 254 nm) for the present study. Linearity was observed in the concentration range of 0.1–100 μg/mL (R2 = 0.9998) with regression equation y = 126698 x – 392.49. The LOQ was found to be 0.08964 µg/mL and the LOD was found to be 0.02913 µg/mL. Stress degradation studies such as acidic, alkaline, oxidation, photolysis and thermal degradations were performed by exposing Bosentan and finally the proposed method was validated as per ICH guidelines. The assay of Bosentan was conducted by applying the proposed method to the marketed formulations. The proposed method is simple, specific, precise, and accurate and can be applied for the estimation of pharmaceutical formulations.

Influence of Bleaching Gel Peroxide Concentration on Color and Penetration through the Tooth Structure

The purpose of this study was to assess the effect of hydrogen peroxide concentration on the bleaching efficacy and penetration through the tooth structure. One hundred enamel/dentin specimens with cylindrical shape were obtained from bovine incisors. The surfaces were polished and the size standardized. They were divided into five groups (n = 20), following the concentration of hydrogen peroxide in the bleaching gels: 20, 25, 30, 35, and 40% (w/w). The specimens were placed over artificial pulpal chambers containing acetate buffer solution and bleached for 30 minutes (three applications of 10 minutes each). Aliquots of the acetate solution were collected, and the peroxide concentration was measured by an analytic spectrophotometer. The color of the samples was analyzed using a colorimetric spectrophotometer at the baseline and 7 days after the bleaching procedure. The color difference was calculated using the ∆Eab formula. The data were analyzed by one-way ANOVA and Tukey's test (p <0.05). The peroxide concentrations of 20-30% showed smaller bleaching effect than the higher concentrations (p = 0.001). The peroxide penetration was significantly higher (p = 0.001) for the more concentrated gels (35 and 40%). The higher peroxide concentrations enhance the bleaching efficacy, but also increased the peroxide penetration through the tooth structure. In-office bleaching gels with higher concentrations of hydrogen peroxide (35 and 40%) present superior whitening efficacy. Nevertheless, they might also intensify the negative biological effects on the pulpal tissue, since they exhibit increased penetration potential. How to cite this article: Torres CRG, Zanatta RF, Godoy MMM, et al. Influence of Bleaching Gel Peroxide Concentration on Color and Penetration through the Tooth Structure. J Contemp Dent Pract 2021;22(5):479-483.

Removal of heavy metals in municipal solid waste incineration fly ash using lactic acid fermentation broth.

Municipal solid waste incineration fly ash (MSWIFA) is considered as a hazardous solid waste because of the high mobility of heavy metals. In this study, the removal of heavy metals in MSWIFA using lactic acid fermentation broth (LAFB) under various leaching protocols (i.e. LAFB addition amount and timing) was investigated. Results revealed that compared with that in pure lactic acid solution, the synergistic effect of various substances in LAFB was more favourable to the dissolution of heavy metals. Although the content of acid-soluble heavy metals in MSWIFA decreased after leaching with LAFB, the leaching toxicity measured by acetic acid buffer solution method increased to varying degrees (except that of Cr). Moreover, the maximum leaching concentration of Pb was 14.1 mg/L (standard limit, 0.25 mg/L), which was not conducive to the landfill treatment of MSWIFA. However, if the LAFB-treated MSWIFA was used in cement kiln for co-disposal, the amount of MSWIFA entering the kiln was 6.0 percentage points higher than that in pure water leaching. Therefore, LAFB leaching instead of water leaching is expected to be an effective pre-treatment method for the utilisation of MSWIFA.

Electrochemical Oxidation of 2,3-Dihydroxypyridine in the Presence of Benzenesulfinic Acid: A Green Method for the Synthesis of a Novel Heterocycle Dye

A green method for the one-pot electrochemical synthesis of a novel highly oxygenated heterocycle dye, 3,8-dihydroxy-4,9-bis(phenylsulfonyl)dipyrano[2,3-b:2′,3′-e]pyrazine-2,7-dione (PSO), is reported. The synthesis of this compound was performed by anodic oxidation of 2,3-dihydroxypyridine (DHP) in the presence of benzenesulfinic acid (BSA) in aqueous acetate buffer solution, using a carbon electrode. The cyclic voltammogram of DHP shows an irreversible anodic peak corresponding to two-electron oxidation of DHP to pyridine-2,3-dione (PDO), while, the CV of the mixture of DHP and BSA exhibits a new anodic peak at more positive potentials which is a confirmation of the reaction between electrogenerated PDO and BSA. Based on the electrochemical evidence, a novel mechanism for the synthesis of PSO is proposed. The synthesis of PSO was conducted in aqueous acetate buffer (pH = 4.0, c = 0.2 M), by controlled potential method (at 0.90 V vs Ag/AgCl electrode, yield 69%) as well as by constant current method (at J = 1.12 mA cm−2, yield 63%) in a divided cell, under green conditions. Furthermore, the pH dependent anodic behavior of 2,3-dihydroxypyridine was investigated. Our data shows that the E pA–pH diagram indicates the presence of five predominant regions. The predominant species across all regions were identified.

Screening of Electrolyte Complexes Formed Between Dextran Sulfate and Amine Structures of Small-Molecule Drugs.

Formation of an electrolyte complex using the electrostatic interactions between a polyanionic polymer and a cationic drug is a simple and efficient method of preparing a colloidal drug carrier system. Dextran sulfate, with a negatively charged sulfate group, was reacted in an acetate buffer solution of pH 3 with positively charged 1° amine, 2° amine, 3° amine, piperazine, and piperidine structures from 24 small-molecule drugs. The electrolyte complex was formed from 15 drugs, 63% of those tested. The tendency to form the electrolyte complex was in the order of piperazine and piperidine >3° amine >>2° amine. The drugs with the 1° amine structure failed to form an electrolyte complex. The mean particle sizes were in the range of 50-740 nm, and most of them showed a submicron colloidal dispersion of <400 nm. Regarding drug encapsulation efficiency (%), 11 drugs with piperazine, piperidine, and 3° amine structures showed 60-98% efficiency, which was fairly high. The results suggest that directly forming the electrolyte complex with dextran sulfate yields promising structural attributes as a submicron colloidal drug carrier system.

A novel, efficient and sensitive method for the simultaneous determination of riboflavin (vitamin B2) and pyridoxine hydrochloride (vitamin B6) in food and pharmacological samples using an electrochemical sensor based on 4,4′-diamino benzophenone

In this study, a method for the sensitive, rapid, efficient and simultaneous determination of the riboflavin (VB2) and pyridoxine (VB6) by voltammetry technique was developed. For this purpose, a novel electrochemical sensor (44-DABP/GC) based on GC electrode modified with 4,4′-diamino benzophenone was fabricated by the cyclic voltammetry. Best analytical performance was obtained in 0.1 M, pH 4.5 acetate buffer solution, with a scanning rate of 100mVs−1, a puls time of 10 ms, a scan increment of 10 mV and a pulse amplitude of 125 mV. 44-DABP/GC electrode exhibited good analytical performance for the determination of VB2 and VB6. Three linear ranges in wide concentration ranges for VB2 from 13 nM to 660 μM, and two linear ranges for VB6 from 15.7 μM to 2210 μM were obtained with the detection limit of 8.52 nM and 4.70 μM, respectively. Besides, repeatability, reproducibility and interference studies were performed. The proposed sensor was applied successfully in food and pharmacological samples.