Perchloric Acid Solutions Research Articles

Polyvinylpyrrolidone as a Corrosion Inhibitor for Carbon Steel in a Perchloric Acid Solution: Effect of Structural Size

Polymers are materials composed of macromolecules characterized by duplicates of smaller molecules that are covalently bonded together to provide a set of properties. Corrosion inhibition by such compounds is usually attributed to their adsorption on the metal-solution interface. The inhibition effect of different sizes of polyvinylpyrrolidone (PVP) on the corrosion of carbon steel (C-steel) in solutions of perchloric acid was investigated. The inhibition efficiency increases as the size of the inhibitor and its concentration increases, but decreases as the temperature increases and can reach a value of 81.53% and 5.0x10^-3 mol L^-1(PVP: 58,000 g mol^-1) at 30°C. The most remarkable inhibition efficiency was confirmed by the presence of the film formed on the metal surface by scanning electron microscopy. The kinetic and thermodynamic parameters for the corrosion of C-steel and adsorption of the inhibitor were determined and discussed. The combination of PVP with potassium iodide produced a strong synergistic effect on the inhibition of C-steel corrosion leading to a significant improvement in the inhibition efficiency. Quantum chemical parameters were studied using density functional theory to determine the possible relationship between the inhibitor and its electronic properties.

A quantitative simulation method for electrochemical infrared and Raman spectroscopies of single-crystal metal electrodes

In-situ electrochemical infrared (EC-IR) and Raman (EC-Raman) spectroscopies are powerful tools for characterizing electrochemical interfacial structures. However, the electrochemical interfaces even for model systems such as single-crystal electrode/electrolyte interfaces are usually very complexly related to the applied potential, adsorbates, electrolyte ions and solvent. As a result, the observed EC-IR and -Raman spectra including the potential-dependent vibrational frequencies and spectral intensities are difficult to be unambiguously interpreted for over four decades. By combining vibrational spectra simulations with electrochemical interface models, we developed a computational method capable of quantitatively simulating EC-IR and EC-Raman spectra observed in the classic metal single-crystal electrochemical systems. In this work, we introduce in detail the theoretical derivation and the optimization of computational parameters for the method. The selections of applied potential, vibrational model, as well as electrode surface configuration are further elaborated for the exact simulation of electrochemical infrared and Raman spectra of the ordered CO adstructures at the Pt(1 1 1) electrode/0.1 M perchloric acid solution interface. The developed method can be expanded to simulate the spectral features in different specific adsorption systems for understanding more complicated materials and interface structures.

Spectroelectrochemical and DFT approaches to the study of croconic acid adsorption at gold electrodes in acidic solutions

• Croconate anions adsorb at Au electrodes in croconic acid-containing solutions. • Croconate species bons in a bidentate configuration with O atoms on top positions. • Adsorption occurs with the molecular plane (quasi) normal to the metal surface. • Adsorption causes significant changes on the geometry and symmetry of croconate. • Collective vibrations broaden and split croconate bands at high coverage. The adsorption of species coming from croconic acid (4,5-dihydroxy-4-cyclopentene-1,2,3-trione, H 2 C 5 O 5 , CA) at gold electrodes was studied spectroelectrochemically in aqueous perchloric acid solutions. Voltammetric experiments suggest the existence of reversible adsorption processes in the potential range between 0.30 and 0.80 V vs RHE. Surface-Enhanced Infrared Reflection Absorption Spectroscopy experiments under Attenuated Total Reflection conditions (ATR-SEIRA) show potential-dependent adsorbate bands in the latter potential range that, according to Density Functional Theory calculations, can be assigned to adsorbed croconate. Calculated optimized geometry corresponds to bonding of croconate species to the gold surfaces involving two oxygen atoms in a bidentate configuration, with the molecular plane perpendicular to the metal surface for low and high crocoanate coverage. For intermediate coverage, lateral repulsions between neighbor croconate adsorbates give rise to the tilting of the molecular plane. The broadening and splitting at high electrode potentials of the C O stretching bands for adsorbed croconate can be explained by invoking the existence of collective vibrational modes appearing at high coverage. The cyclic voltammograms recorded in the CA-containing solutions also show the existence of reversible redox processes at potentials below 0.30 V involving adsorbed species, which are detected in the collected ATR-SEIRA spectra.

Oxygen Reduction on Glassy Carbon-Supported PdAu Nanoparticles in Perchloric Acid Solution

Oxygen Reduction on Glassy Carbon-Supported PdAu Nanoparticles in Perchloric Acid Solution

Structure-Dependence of the Atomic-Scale Mechanisms of Pt Electrooxidation and Dissolution

For current low-temperature hydrogen-oxygen fuel cells, as used e.g. in the upcoming generation of commercial fuel cell vehicles, platinum is still the catalyst of choice, especially for the cathode side. However, catalyst lifetime and performance remain a problem for large-scale commercialization. It has been known for some time that electrochemical oxidation and subsequent oxide reduction lead to irreversible structural changes as well platinum dissolution but the fundamental understanding of these complex processes is still rudimentary. A detailed atomistic picture of the steps by which these ultrathin oxide layers form existed up to now only for the close-packed Pt(111) surface [1]. Here, previous in situ studies by surface X-ray diffraction (SXRD) techniques established the precise locations of the first Pt atoms that move out of their lattice sites in a place-exchange process [2] and found good agreement with density functional theory (DFT) calculations [3]. Provided the potential is not too high, these atoms can move back to their original locations, but at higher potentials an irreversible restructuring of the surface occurs.To elucidate the role of the Pt surface structure, we performed in-depth comparative studies of Pt(111) and Pt(100) in perchloric acid solution by in situ SXRD, online inductively coupled plasma mass spectrometry (ICP-MS) and DFT [4]. Clear differences were found, which mirror the differences in the dissolution behavior of the two electrode surfaces (Figure 1a). Pt(100) not only start to dissolve at lower potential but its oxidation also immediately changes its surface structure in an irreversible manner. These observations demonstrate clearly that Pt dissolution is linked to the way Pt atoms are initially extracted from the surfaces during oxidation.For a better understanding of the extraction process on Pt(100), we performed surface diffraction studies at ESRF ID31 with very high photon energies of 70 keV (HESXRD) [5]. This technique was employed for the first time to a solid-liquid interface and proofed to be indispensable for clarifying the oxide’s structure. The oxidation-induced changes, exemplified in figure 1b for one out of twelve simultaneously measured crystal truncation rods, can be unambiguously assigned to a process in which the extracted Pt atom moves laterally away from its original site. This initiates the immediate extraction of a second atom, leading to the formation of atomic oxide stripes on the surface (see figure 1c). DFT calculations support this scenario and show that, differently from Pt(111), this mechanism produces unstable surface atoms at stripe ends that can dissolve during the oxidation as well as during the subsequent oxide reduction. Consequently, the extraction process on Pt(100) is irreversible from its very onset.These results show a high sensitivity of Pt electrocatalyst oxidation and degradation to the precise surface structure. Rational strategies for the design of catalysts with improved stability will have to take the different mechanisms into account.[1] J. Drnec, D.A. Harrington, O.M. Magnussen, Curr. Op. Electrochem., 4, 69-75 (2017)[2] M. Ruge, et al., J. Electrochem. Soc., 164, H608-H614 (2017)[3] M. J. Eslamibidgoli,, M. H. Eikerling, Electrocatalysis, 7, 345–354 (2016)[4] T. Fuchs, et al., Nat. Catal., 3, 754-761 (2020)[5] J. Gustafson, et al., Science, 343, 758–761 (2014) Figure 1. (a) correlation between Pt(hkl) dissolution and restructuring behavior in 0.1 M HClO4. (b) Example of Pt(100) crystal truncation rod changes with increasing oxidation, measured by in situ high-energy surface X-ray diffraction. (c) Pt extraction mechanisms, obtained from DFT calculations (adapted from T. Fuchs, et al., Nat. Catal., 3, 754 (2020)). Figure 1

Surface charge and interfacial acid-base properties: pKa,2 of carbon dioxide at Pt(110)/perchloric acid solution interfaces.

In this work, we investigate the in-situ spectro-electrochemical behavior of Pt(110) electrodes in contact with acid solutions saturated with CO2. Similar to previous observations reported for Pt(111) electrodes, potential-dependent signals associated to adsorbed bicarbonate and carbonate anions are observed in the FT-IRRA spectra collected for Pt(110), even when the concentration of these anions are near to zero in the bulk solution. The relative intensities of the infrared bands at different pH and applied potential values can be used to determine the interfacial pKa,2 of CO2. The surface pKa,2 value found for Pt(110) electrodes is lower than that for Pt(111) electrodes. This result can be interpreted by assuming that the more open (110) surface leads to a more alkaline interphase than the close packed (111), in the sense that it reacts with acids in a higher extent. We attribute this difference to the lower potential of zero free charge and work function values for Pt(110) electrodes compared to Pt(111) electrodes.

Determination of 8 biogenic amines in aquatic products and their derived products by high-performance liquid chromatography-tandem mass spectrometry without derivatization

A method for the determination of 8 biogenic amines in aquatic products and their derived products was established by HPLC-MS/MS without derivatization. The samples were extracted by 5% perchloric acid solution. N-hexane was used to clean the extract. The analytes were separated by a column of ACQUITY UPLC HSS T3 (100 mm × 2.1 mm, 1.8 µm), and gradient eluted with a mixed solution of (0.5% formic acid) and acetonitrile. Good linearity was obtained with correlation coefficients (R2) >0.99. This method achieved higher sensitivity (from 0.1 mg/kg for tyramine, 2-phenylethylamine and tryptamine to 1.0 mg/kg for spermidine, spermine, cadaverin, histamine and putrescine). The average recoveries were demonstrated in the range of 70.9%–113.1%, with relative standard deviations (RSDs) from 0.33% to 10.81%. This method was suitable for the detection of BAs in aquatic products and their products.

Determination of clemastine by the HPLC method in the blood

Topicality. Сlemastine fumarate (tavegil)-1-methyl-2 [2-α-methyl-p-chlorobenzhydryloxy)-ethyl]-pyrrolidine fumarate is the first generation H1-histamine receptor blocker. Сlemastine fumarate selectively inhibits histamine H1 receptors and reduces capillary permeability. The drug has a pronounced anti-allergic and antipruritic effect. Clemastine prevents the development of vasodilation and the smooth muscle contraction induced by histamine. Сlemastine fumarate has an isignificant anticholinergic activity, causes sedation. The drug is used to treat pruritus in psoriasis, multiple sclerosis and optic neuritis. Clemastine is characterized by the following side effects: increased fatigue, drowsiness, sedation, weakness, lethargy, impaired coordination of movements; nausea, vomiting, decreased blood pressure, palpitations, hemolytic anemia, skin rash, anaphylactic shock. In case of an overdose, the drug has a neurotoxic effect, which manifests itself in impaired consciousness with the development of generalized anticholinergic convulsive syndrome. The urgent task for monitoring the treatment effectiveness of the population with сlemastine fumarate and diagnosis of drug intoxication is the choice of highly sensitive and selective research methods of its analysis in pharmaceuticals and biological matrices during the treatment. Aim. To develop an algorithm for directed analysis of clemastine in biological extracts from the blood using a unified method of the HPLC research. Materials and methods. The extraction of clemastine was performed with chloroform at Ph 9.0. The extracts were purified from impurities by a combination of TLC and extraction with hexane. The TLC purification and identification of clemastine were carried out under optimal conditions: the system of organic solvents – methanol – 25 % solution of ammonium hydroxide (100 : 1.5) and chromatographic plates – Sorbfil PTLC-AF-A, Rf сlemastine = 0.60 ± 0.03. To detect clemastine, the most sensitive location reagents were used –UV light (λ = 254 nm) and Dragendorff’s reagent modified by Mounier. The chromatographic analysis was performed on a “Milichrome A-02” microcolumn liquid chromatograph (EkoNova, Closed Joint-Stock Company, Russia) under standardized HPLC conditions: the reversed-phase variant using a metal column with a non-polar absorbent Prontosil 120-5C 18 AQ, 5 μm; the mobile phase in the linear gradient mode – from eluent А (5 % acetonitrile and 95 % buffer solution – 0.2 М solution of lithium perchlorate in 0.005 М solution of perchloric acid) to eluent B (100 % acetonitrile) for 40 min. Regeneration of the column was conducted for 2 min with the mixture of solvents; the flow rate of the mobile phase was 100 μl/min, the injection volume – 4 μl. The multichannel detection of the substance was performed using a two-beam multi-wave UV spectrophotometer at 8 wavelengths of 210, 220, 230, 240, 250, 260, 280, and 300 nm; the optimal value of the column temperature – 37-40 °С and the pump pressure – 2.8-3.2 MPa. Results and discussion. Isolation of clemastine from the blood was performed according to the method developed, including the extraction with chloroform at pH 9.0; the extraction purification of extracts with hexane from impurities; the TLC purification and identification of clemastine. Using the unified HPLC method clemastine was identified by retention parameters and spectral ratios. For the quantitative determination, a calibration graph or the straight line equation corresponding to this graph were used. The results obtained indicated the reliability and reproducibility of the method. It was found that the relative uncertainty of the average result in the analysis of clemastine in the blood was ε = ± 4.63 %, the relative standard deviation of the average result was RSDx = 1.67 %. Conclusions. Clemastine was extracted with chloroform at pH 9.0 from the blood. Purification of extracts from co-extractive compounds was performed by combining TLC and extraction with hexane. It has been found that when isolating сlemastine from the blood according to the methods developed it is possible to determine 36.05-39.55 % of the substance (ε = ± 4.63 %, RSDx = 1.67 %). The method of TLC purification and identification of сlemastine in biogenic extracts was tested under the optimal conditions: the system of organic solvents – methanol – 25 % solution of ammonium hydroxide (100 : 1.5), the use of reagents – UV light, Dragendorff’s reagent modified by Mounier, Rf сlemastine = 0.60 ± 0.03 (Sorbfil PTLC-AF-A). The unified HPLC method for identification and quantification of сlemastine was tested in biogenic extracts from the blood according to the algorithm of the directed analysis developed. It has been found that сlemastine can be identified by the retention time – 25.997-26.011 min; the retention volume – 2599.7-2601.1 μl; spectral ratios – 0.741; 0.536; 0.096; 0.023; 0.027; 0.005; 0.003. The сlemastine content was determined by the equation S = 0.15 · 10-3 С + 0.14 · 10-3; the correlation coefficient was equal to 0.9998. Chromatographic methods can be recommended for implementation in practice of the Bureau of Forensic Medical Examination, poison control centers, clinical laboratories regarding the study of medicinal substances in biological objects.

Recovery of Cu(II) by Acorga M5640 After Leaching of Malachite Ore in Perchloric Acid Solutions

Recovery of Cu(II) by Acorga M5640 After Leaching of Malachite Ore in Perchloric Acid Solutions

Effect of Hydrophobic Cations on the Inhibitors for the Oxygen Reduction Reaction on Anions and Ionomers Adsorbed on Single-Crystal Pt Electrodes.

Weakening of the poisoning by the specifically adsorbed anions assists in developing next-generation electrocatalysts for use in low-temperature fuel cells. In this study, we evaluated how hydrophobic cations with different alkyl chain lengths affect the oxygen reduction reaction (ORR) activities on the single-crystal Pt surfaces in contact with sulfuric acid solution and Nafion ionomers. Interfacial tetraalkylammonium cations with longer alkyl chains activated the ORR on the Pt(111) surface. In a solution containing tetrahexylammonium cations (THA+), the ORR activities on Pt(111) in sulfuric acid solution and on Nafion-modified Pt(111) in perchloric acid solution were four and eight times higher than those in the solutions without THA+, respectively. Infrared spectroscopy revealed the reduction of the amount of (bi)sulfate anions and the sulfonate group of Nafion adsorbed on Pt(111) due to the presence of THA+. The hydrophobic cations weaken the noncovalent interactions between specifically adsorbed species and promote the ORR.

Extraction of REE(III), U(VI), and Th(IV) from Perchloric Acid Solutions with 2,6-Bis(diphenylphosphorylmethyl)pyridine N-Oxide

The extraction of microamounts of REE(III), U(VI), and Th(IV) from HClO4 solutions with solutions of 2,6-bis(diphenylphosphorylmethyl) pyridine N-oxide (I) in 1,2-dichloroethane was studied depending on the HClO4 concentration in the equilibrium aqueous phase. The stoichiometry of the extracted complexes was determined. It was shown that compound I extracts REE(III), U(VI), and Th(IV) from dilute HClO4 solutions with much higher efficiency than from HNO3 solutions. With an increase in the concentration of acids, the magnitude of the “perchlorate” effect upon extraction of REE(III) and U(VI) decreases, and Th(IV) is extracted by compound I from HClO4 solutions with lower efficiency than from HNO3 solutions.

Study of Sorption of Eu(III) from Various Media on TODGA-Сontaining Sorbent AXIONIT MND40T

The dependences of the static capacity (SC) of the AXIONIT MND40T sorbent based on tetraoctyldiglycolamide (TODGA) for Eu(III) on the concentration of HNO3, HCl, H2SO4, and HClO4 were determined. The SC increases with increasing acid concentration. In the concentration range 2–4 mol dm–3 SC of AXIONIT MND40T for europium in nitric, hydrochloric, and perchloric acid solutions is approximately the same, whereas in sulfuric acid solutions it is much lower. The maximum capacity and adsorption constant (Kad) in different media were calculated from the results of processing of the isotherms of europium sorption by AXIONIT MND40T. The mechanism for the extraction of europium from nitric acid solutions by AXIONIT MND40T is proposed based on the IR spectroscopy data.

Preparation of Unique Flower-like Pt-Ni Alloy Catalysts As the Cathode of a PEMFC By Electrodeposition Technique

The hydrogen economy can play an important role in the low-carbon economy, and fuel cells technology is an essential part of the hydrogen economy. The proton exchange membrane fuel cell (PEMFC) is one kind of electrochemical reaction device with the advantages of low temperature operation, high conversion efficiency and noiseless, which is expected to widely utilizes in public transportations.The oxygen reduction reaction (ORR) at the cathode is the rate-determining step in PEMFC. To enhance the ORR activity at the cathode, the unique flower-like platinum-nickel binary alloy catalysts were electrodeposited on the commercial carbon cloth by potentiostatic electrodeposition technique, the PtNi alloy effectively improved the oxygen adsorption and desorption paths on the surface. The PtNi alloy catalysts with shorter lattice distance and effects of high-index facets would increase the electrochemical surface area (ECSA) of the catalysts and power density of fuel cell. The samples of the pure platinum and commercial Pt/C catalyst were also prepared as comparison.Morphology, particle size and elemental composition were characterized by SEM, XRD and ICP-MS. In addition, the electrochemical characteristics of the PtNi catalysts were investigated via cyclic voltammetry (CV) and linear sweep voltammetry (LSV) analysis in 0.1 M perchloric acid solution with rotating disk electrode (RDE). In single cell test, the maximum peak power density of PEMFC with homemade PtNi alloy catalyst as the cathode reached 1031 mW/cm2, enhancing about 12% power density, compared to the commercial Pt/C. Figure 1

Oxidation of barbituric and thiobarbituric acids by chromium trioxide in different acidic media: A kinetic and mechanistic aspects

Kinetics and mechanism of oxidation of two biologically reactive heterocyclic compounds, namely, barbituric (BA) and thiobarbituric (TBA) acids by chromium trioxide (CrVI) have been explored using UV–Vis absorption spectra in sulfuric and perchloric acid solutions at fixed ionic strength of 2.0 mol dm−3 and a temperature of 298 K. The oxidation reactions demonstrated a 3:4 stoichiometry (organic acid: CrVI). The reactions kinetics in the examined acidic media were set to be first order with admiration to [CrVI] and fractional orders in organic acid and H+ concentrations. Varying the ionic strengths and dielectric constants of the reaction media had no noteworthy influence on the reactions’ rates. Tests for free radicals involvement throughout the reactions were positive. Addition of chromium(III) as a predicted oxidation product did not considerably alter the rates whereas addition of manganese(II) diminished the oxidation rates. Supplementation of some divalent transition metal ions increased the oxidation rates. At same investigational circumstance, the rates of BA oxidation in both acidic media were set to be about 20–30% higher than those of TBA, and those acquired in sulfuric acid were also found to be higher than those of perchloric acid solutions for both BA and TBA with almost the same percentages. The oxidation products of BA and TBA were described as 2,4,5,6-pyrimidinetetraone (alloxan) and 2-thio-4,5,6-pyrimidinetrione, respectively. A conceivable oxidation mechanism has been anticipated. The derived rate-law expression was in a good agreement with the investigational outcomes. The activation parameters with regard to the second order rate constants were assessed and debated. The existing study presents an unprecedented simple and inexpensive treatment method for removal of certain pollutants for saving the environment and human health.

Reprint of "Effect of tin deposition over electrogenerated random defects on Pt(111) surfaces onto ethanol electrooxidation: Electrochemical and FTIR studies"

In the present study, random superficial defects of the {110}-type were electrogenerated on an initially well-ordered Pt(111) single crystal electrode, by cycling the potential in the range from 0.05 to 1.30 V by 32 times in perchloric acid solution and in a scan rate of 0.05 V s−1, named as Pt(111)-32. After partial disordering of the electrode surface, it was modified by deposition of tin submonolayers in three different coverage degrees of Sn, namely, ѲSnDefects= 0.34, 0.54 and 1.0. The Sn is preferentially deposited on the {110}-type defects generated previously. The effect of tin over the electrocatalytic activity for the ethanol electrooxidation reaction (EOR) and CO oxidation was investigated by using cyclic voltammetry, while the mechanism of the alcohol oxidation on the unmodified and Sn-modified electrodes was investigated by using in situ Fourier Transform Infrared (FTIR) spectroscopy. The lower Sn coverage degree on defect sites (ѲSnDefects= 0.34) showed, in the first voltammetric cycle, very good performance for EOR, having a peak current at 0.58V twice the one observed for the unmodified Pt(111)-32 electrode. However, the situation changed in the second voltammetric cycle, where on the full Sn covered defect sites electrode (ѲSnDefects= 1) a better electrocatalytic response was observed with more tolerance to the strongly adsorbed blocking intermediate species at low potentials. Additionally, it was found that this behavior should be in part associated with the ability of this electrode decorated with Sn to oxidize CO at a lower potential than those observed for other surfaces. The production of CO2 and acetic acid is enhanced as the Sn coverage degree also increases, as shown by FTIR, however, the later product is the majority product of this reaction for all the investigated electrodes. Thus, the main effect of Sn is reflected in the increased production of acetic acid.

Development of a Rapid and Eco-Friendly UHPLC Analytical Method for the Detection of Histamine in Fish Products.

We developed, validated, and confirmed with proficiency tests a fast ultra-high-performance liquid chromatography with diode array detector (UHPLC-DAD) method to determine histamine in fish and fishery products. The proposed method consists of two successive solid–liquid extractions: one with a dilute solution of perchloric acid (6%) and the second only with water. The instrumental analysis with UHPLC provides a very fast run time (only 6 min) with a retention time of approximately 4 min, a limit of quantification (LOQ) of 7.2 mg kg−1, a limit of detection (LOD) of 2.2 mg kg−1, a recovery around 100%, a relative standard deviation (RSD%) between 0.5 and 1.4, and an r2 of calibration curve equal to 0.9995. The method detected optimal values of the validation parameters and required a limited number of reagents in comparison to other methods reported in the literature. Furthermore, the method could detect histamine in a very short time compared with other methods. This method, in addition to being validated, precise, specific, and accurate, avoids wasting time, money, and resources, and limits the use of organic solvents.

Effect of anions on electrodeposition of structured platinum nanocrystallites

Pulsed (square–wave) electrodeposition of platinum nanocrystallites with a high concentration of (100) regions from a H2PtCl6 solution with different background anions is studied. The effect of the background electrolyte is shown, namely, a more perfect cubic faceting of crystallites obtained in the 0.1 M HClO4 solution as compared to 0.5 M H2SO4. A procedure for deposit formation (secondary growth) with intermediate pulsed treatment in acid is suggested that does not involve application of high negative/positive overpotentials (no additional increasing of the mobility of platinum atoms). This allows preserving the crystallite structure and improving the overall deposit structure. In addition to conventional methods of fine surface structure determination on the basis of the hydrogen UPD region in cyclic voltammograms in sulfuric acid and SEM, we propose analysis of the Pt(100) terrace concentration/width based on the characteristic peak of nitrate ion reduction in voltammograms in perchloric acid. Stepped Pt single crystals with (100) terraces of different width are used for comparison. The effect of solution temperature on formation of faceted crystallites is shown and the optimum deposition temperature is determined: the optimum temperature in perchloric acid solution is 40 °C, while an increase in the temperature in sulfuric acid solutions results under the chosen conditions in deposition acceleration and an increase in the amount of surface defects.

Simultaneous identification and determination of biogenic amines in Pueraria lobata by ultra-high performance liquid chromatography

A method of ultra-performance liquid chromatography (UPLC) with precolumn derivatization has been established for identification and simultaneous determination of nine biogenic amines as tryptamine, phenethylamine, putrescine, cadaverine, histamine, octopamine, tyramine, spermidine and spermine in pueraria lobata. Samples were extracted with perchloric acid solution, derivitazation with dansyl chloride, added ammonia water for termination reaction and then made up to the desired volume with acetonitrile. The chromatographic separation was performed on Acquity UPLC BEH C18 column (2.1 mm × 100 mm, 1.7 μm) using 5 mmol/L ammonium acetate and acetonitrile as mobile phase for gradient elution at the flow rate of 0.4 mL/min. Photo-diode array detector was set at wavelength of 254 nm for all of the biogenic amines. Nine biogenic amines had good linear relationships in the concentration range of 0.1–20 μg/mL with correlation coefficients larger than 0.999. The recoveries of samples spiked at levels of 20, 50 and 100 mg/kg were 75.6–97.2% with the relative standard deviations of 0.12–5.32% (n = 6). The limits of detection of the nine biogenic amines were all 10 mg/kg. The established method is simple, rapid and sensitive, which can be used for simultaneous determination of nine biogenic amines residues in Pueraria lobata and other plant medicine. By the established method, it was the first time to verify that there are biogenic amines in Pueraria lobata all over the world, which would be used to study the health care mechanism of Pueraria lobata for people.

English

English

Experimental and Theoretical Studies of Eosin Y Dye as Corrosion Inhibitors for Carbon Steel in Perchloric Acid Solution

The adsorption behavior and the inhibition performance of Eosin Y Dye for carbon steel corrosion in 1 M perchloric acid solution have been carried using weight loss and scanning electron micrograph (SEM) techniques as well theoretical calculations based on density functional theory (DFT). The studied inhibitor concentrations were between 5´10-5 M and 5´10-3 M. Results obtained revealed that Eosin Y is an effective inhibitor and its inhibition efficiency increases with increasing concentration to attain 96.91% at 5´10-3 M at 30 °C. Thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy were obtained from experimental data of the temperature studies of the inhibition process at five temperatures ranging from 20 to 60 °C. It was found that the adsorption of Eosin Y could prevent steel from weight loss and the adsorption accorded with the Langmuir adsorption isotherm. The free energy of adsorption showed that the corrosion inhibition takes place by spontaneous physicochemical adsorption of inhibitor molecules on the carbon steel surface. SEM and DFT studies confirm the adsorption of Eosin Y on carbon steel surface. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).