Impurity Levels Research Articles

Assessment of Phytochemical Constituents, Antimicrobial Activity, Impurity and Heavy Metal Content of Gynura nepalensis

This study explores the multifaceted area of herbal medicine, focusing on Gynura nepalensis, a medicinal plant. The qualitative analyses confirmed the presence of alkaloids, glycosides, phenols, tannins, flavonoids, protein-amino acids, saponins, and carbohydrates. Terpenoids and resin were apparently missing. The antimicrobial activity of the plant extract was assessed and it revealed dose-dependent efficacy against microbial growth. Additionally, the study scrutinized the total ash content, suggesting a moderate level of impurity, and evaluated the heavy metal concentration, finding it well below acceptable limits. Overall, the findings establish the promising role of Gynura nepalensis in natural medicine, urging further investigations and potential applications in integrated healthcare. Bangladesh Pharmaceutical Journal 27(2): 193-200, 2024 (July)

First-Principles Insights into Highly Sensitive and Reusable MoS2 Monolayers for Heavy Metal Detection.

This study explores the potential of MoS2 monolayers as heavy metal sensors for As, Cd, Hg, and Pb using density functional theory (DFT) and Non-Equilibrium Green's Function (NEGF) simulations. Our findings reveal that As and Pb adsorption significantly alters the surface structure and electronic properties of MoS2, introducing impurity levels and reducing the band gap. Conversely, Cd and Hg exhibit weaker interactions with the MoS2 surface. The MoS2 monolayer sensors demonstrate exceptional sensitivity for all four target heavy metals, with values reaching 126,452.28% for As, 1862.67% for Cd, 427.71% for Hg, and 83,438.90% for Pb. Additionally, the sensors demonstrate selectivity for As and Pb through distinct response peaks at specific bias voltages. As and Pb adsorption also induces magnetism in the MoS2 system, potentially enabling magnetic sensing applications. The MoS2 monolayer's moderate adsorption energy facilitates rapid sensor recovery at room temperature for As, Hg, and Cd. Notably, Pb recovery time can be significantly reduced at elevated temperatures, highlighting the reusability of the sensor. These results underscore the potential of MoS2 monolayers as highly sensitive, selective, and regenerable sensors for real-time heavy metal detection.

Elemental Impurity Analysis in Five Different Types of Coffee: Assessment of Carcinogenic and Non-carcinogenic Risks

In the study, the levels of Cd, Pb, As, and Hg elemental impurities potentially present in coffee bean samples from Indonesia, Kenya, Colombia, Guatemala, and Türkiye were determined using chromatographic analysis, and the analysis results were utilized to assess the risks on human health. The risk assessment of coffee was calculated for one or three servings per day for 365 days a year. Exposure to coffee consumption was calculated according to age groups of young adults and middle-aged adults (20-65 years). When Cd, Pb, As and Hg levels in coffee samples were analyzed, Cd in coffee samples was found to be in the range of approximately 3.70 - 5.89 µg/kg, Pb in the range of 25.68-41.11 µg/kg, As in the range of 1.45-6.64 µg/kg and Hg in the range of 1.06-5.06 µg/kg. Hazard Index (HI) values for all elements in the assessment of non-carcinogenic risks were found to be <1.0. When the cancer risk (CR) value was calculated for Cd, Pb, and As, it was found that the CR value did not exceed the United States Environmental Protection Agency (USEPA) criteria in all coffee samples in both scenarios. Considering the assessment of the health risks of elemental impurities in five different coffee bean samples, it was concluded that all samples' CR and HI values did not exceed the USEPA criteria.

CONSTRUCTIVE-FUNCTIONAL ANALYSIS AND SIZING OF HYDRAULIC FILTERS

The reliability of hydrostatic installations depends on the low level of impurities in an environment with pressure at an allowable value, which avoids an accentuated wear of the individual elements of the installations. Hydraulic filters are elements that have a role in protecting the hydrostatic installations from the particles that are found in the hydraulic oil. The paper aims to present some of the elements underlying the construction of hydraulic environment filtration equipment, certain conditions that are imposed on them, as well as the main problems related to the calculation and sizing of filters.

Redefining water purification: gC3N4-CLDH's electrochemical SMX eradication

The contamination of water sources by pharmaceutical compounds presents global environmental and health risks, necessitating the development of efficient water treatment technologies. In this study, the synthesis, characterization, and evaluation of a novel graphitic carbon nitride-calcined (Fe–Ca) layered double hydroxide (gC3N4-CLDH) composite for electrochemical degradation of sulfamethoxazole (SMX) in water yielded significant outcomes are reported. SEM, XRD, FTIR, and XPS analyses confirmed well-defined composite structures with unique morphology and crystalline properties. Electrochemical degradation experiments demonstrated >98% SMX removal and >75% TOC removal under optimized conditions, highlighting its effectiveness. The composite exhibited excellent mineralization efficiency across various pH levels, with superoxide radicals (O2●–) and hydroxyl radicals (●OH) identified as primary reactive oxygen species. With remarkable regeneration capability for up to 7 cycles, the gC3N4-CLDH composite emerges as a highly promising solution for sustainable water treatment. Humic acid (HA) in water significantly slows SMX degradation, suggests complicating SMX degradation with natural organic matter. Despite this, the gC3N4-CLDH composite effectively degrades SMX in groundwater and industrial wastewater, with slight efficiency reduction in the latter due to higher impurity levels. These findings highlight the complexities of treating pharmaceutical pollutants in various water types. Overall, gC3N4-CLDH's high removal efficiency, broad pH applicability, sustainability, and mechanistic insights provide a solid foundation for future research and real-world environmental applications.

Enhanced Stability and Compatibility of Montelukast and Levocetirizine in a Fixed-Dose Combination Monolayer Tablet.

The purpose of this study was to enhance the stability of montelukast and levocetirizine for the development of a fixed-dose combination (FDC) monolayer tablet. To evaluate the compatibility of montelukast and levocetirizine, a mixture of the two drugs was prepared, and changes in the appearance characteristics and impurity content were observed in a dry oven at 60 °C. Excipients that contributed minimally to impurity increases were selected to minimize drug interactions. Mannitol, microcrystalline cellulose, croscarmellose sodium, hypromellose, and sodium citrate were chosen as excipients, and montelukast-levocetirizine FDC monolayer tablets were prepared by wet granulating the two drugs separately. A separate granulation of montelukast and levocetirizine, along with the addition of sodium citrate as a pH stabilizer, minimized the changes in tablet appearance and impurity levels. The prepared tablets demonstrated release profiles equivalent to those of commercial products in comparative dissolution tests. Subsequent stability testing at 40 ± 2 °C and 75 ± 5% RH for 6 months confirmed that the drug content, dissolution rate, and impurity content met the specified acceptance criteria. In conclusion, the montelukast-levocetirizine FDC monolayer tablet developed in this study offers a potential alternative to commercial products.

Effect of Substitutional Metallic Impurities on the Optical Absorption Properties of TiO2.

(TiO2) is both a natural and artificial compound that is transparent under visible and near-infrared light. However, it could be prepared with other metals, substituting for Ti, thus changing its properties. In this article, we present density functional theory calculations for Ti(1-x)AxO2, where A stands for any of the eight following neutral substitutional impurities, Fe, Ni, Co, Pd, Pt, Cu, Ag and Au, based on the rutile structure of pristine TiO2. We use a fully unconstrained version of the density functional method with generalized gradient approximation plus the U exchange and correlation, as implemented in the Quantum Espresso free distribution. Within the limitations of a finite-size cell approximation, we report the band structure, energy gaps and absorption spectrum for all these cases. Rather than stressing precise values, we report on two general features: the location of the impurity levels and the general trends of the optical properties in the eight different systems. Our results show that all these substitutional atoms lead to the presence of electronic levels within the pristine gap, and that all of them produce absorptions in the visible and near-infrared ranges of electromagnetic radiation. Such results make these systems interesting for the fabrication of solar cells. Considering the variety of results, Ni and Ag are apparently the most promising substitutional impurities with which to achieve better performance in capturing the solar radiation on the planet's surface.

SynONIM: A Comprehensive Database of Synthetic Oligonucleotide Modifications and Impurities to Aid in Their Characterization by Mass Spectrometry.

Given the resurgence of oligonucleotides in the biotherapeutic space, there is a profound focus on their characterization by mass spectrometry. These therapeutic moieties commonly employ synthetic modifications to aid in increasing efficacy and stability; however, these modifications can also increase the complexity of mass spectrometry data analysis. Additionally, various stress conditions can affect both the observed level and type of impurities stemming from the variety of utilized modifications. Within the oligonucleotide analytical development community, a clear desire exists for a unified database of synthetic oligonucleotide modifications and impurities where information regarding structure, mass, and shorthand nomenclature can be contained. To address this, the authors have prepared an online database and webtool of synthetic oligonucleotide impurities and modifications, SynONIM, to centrally locate information key to the mass spectrometry community. SynONIM can be queried by elemental composition lost or gained, mass shift, shorthand notation, nucleotide location, and species origin.

Simultaneous effect of oxygen impurity and flow rate of purge gas on adsorption capacity of and heel buildup on activated carbon during cyclic adsorption-desorption of VOC

Irreversible adsorption, or heel buildup, negatively impacts activated carbon performance and shortens its lifetime. This study elucidates the interconnections between flow rate and the oxygen impurity of desorption purge gas with heel buildup on beaded activated carbon (BAC). Nine thermal desorption scenarios were explored, varying nitrogen purge gas oxygen impurity levels (<5 ppmv, 10,000 ppmv, 210,000 ppm (21 %)) and flow rates (0.1, 1, 10 SLPM or 1 %, 10 %, 100 % of adsorption flow rate) during thermal desorption. Results reveal that increasing purge gas flow rate improves adsorption capacity recovery and mitigates adverse effects of purge gas oxygen impurity. Cumulative heel increased with higher purge gas oxygen impurity and lower flow rates. In the least effective regeneration scenario (0.1 SLPM N2, 21 % O2), a 32.8 wt% cumulative heel formed on BAC after five cycles, while the best-case scenario (10 SLPM N2, <5 ppmv O2) resulted in only 0.3 wt%. Comparing the pore size distributions of virgin and used BAC shows that heel initially forms in narrow micropores (<8.5Å) and later engages mesopores. Thermogravimetric analysis (TGA) showed that oxygen impurity creates high boiling point and/or strongly bound heel species. TGA confirmed that higher purge gas flow rates reduce heel amounts but encourage chemisorbed heel formation in oxygen's presence. These findings can guide optimization of regeneration conditions, enhancing activated carbon's long-term performance in cyclic adsorption processes.

Synergistic effect of interstitial phosphorus doping and MoS2 modification over Zn0.3Cd0.7S for efficient photocatalytic H2 production

ZnxCd1-xS photocatalysts have been widely investigated due to their diverse morphologies, suitable band gaps/band edge positions, and high electronic mobility. However, the sluggish charge separation and severe charge recombination impede the application of ZnxCd1-xS for hydrogen evolution reaction (HER). Herein, doping of phosphorus (P) atoms into Zn0.3Cd0.7S has been implemented to elevate S vacancies concentration as well as tune its Fermi level to be located near the impurity level of S vacancies, prolonging the lifetime of photogenerated electrons. Moreover, P doping induces a hybridized state in the bandgap, leading to an imbalanced charge distribution and a localized built-in electric field for effective separation of photogenerated charge carriers. Further construction of intimate heterojunctions between P-Zn0.3Cd0.7S and MoS2 accelerates surface redox reaction. Benefiting from the above merits, 1 % MoS2/P-Zn0.3Cd0.7S exhibits a high hydrogen production rate of 30.65 mmol·g−1·h−1 with AQE of 22.22 % under monochromatic light at 370 nm, exceeding most ZnxCd1-xS based photocatalysts reported so far. This work opens avenues to fabricate examplary photocatalysts for solar energy conversion and beyond.

Silane functionalized cardanol/calcium carbonate epoxy‐reinforced polymer nanocomposites for sustainable microwave absorption applications

AbstractMicrowave absorption properties of epoxy resin/cardanol (ER/C) and epoxy resin/silane functionalized cardanol (ER/SFC) nanocomposites with various percentages of calcium carbonate nanoplatelets (CCNPs) studied in the frequency range of 8–18 GHz. The CCNPs obtained from the mussel shell were reinforced into a cardanol‐toughened ER matrix to mimic the composite structure of the abalone shell. The phase separation between ER, SFC, and CCNPs encapsulated in a polymer matrix was analyzed with SEM, and the presence of a low level of Fe3O4 magnetic impurities of 0.007 emu/g present as shown and verified by XRD and VSM analyses. The nanocomposites with ER/SFC/CCNPs 3 wt.% demonstrate a high surface roughness of 3.467 nm and an enhanced hydrophobicity, as indicated by a high contact angle of 102°. The silanization‐induced localization of CCNPs facilitates a mutually conducive morphology for excellent viscoelastic and microwave absorption properties. The increase in damping factor ratio of approximately 0.85 augments the microwave absorption property and it observed that ER/SFC/CCNPs 3 wt.% nanocomposites show higher reflection loss (RL) of more than 99.9% with RL of −43 dB at 12 GHz. The research aims to fabricate cost‐effective and multifunctional nanocomposites for microwave absorption applications.Highlights Excellent hydrophobicity owing to the surface roughness of 3.467 nm. Maximum contact angle of 102.1° due to the reinforcement of CCNPs and SFC to the epoxy matrix. Efficient microwave attenuation due to the reflection loss of −43 dB. Excellent microwave absorption of 99.99% with a damping factor of 0.85. Higher storage modulus due to the strong inter‐penetrating network of the composite.

Study of vacancy defect in 2D/3D semiconductor heterostructure based on monolayer WSe2 and GaN

2D/3D heterostructure have attracted considerable attention within the scientific community due to their superior electronic properties and extensive spectral absorption capabilities. However, structural defect is inevitably introduced during the synthesis of 2D materials, which can significantly alter their intrinsic physical properties. Hence, 2D/3D semiconductor heterostructure composed of monolayers of WSe2 and GaN are constructed using first-principles calculations in this study. The impact of vacancy defect on the geometrical, electronic, and optical properties of the WSe2/GaN heterostructure is then systematically explored. The electronic property reveals that the introduction of impurity levels by vacancy defect, as well as interlayer surface-suspended bonds, results in a reduced band gap. This modification enhances the transfer ability of electrons from the valence band to the conduction band. Optical characterization demonstrates that the heterostructure formed by WSe2 and GaN exhibits a broad absorption spectrum, spanning from the visible to ultraviolet region, indicating a dual-wavelength photoresponse. Furthermore, regarding absorption coefficient and reflectivity, the heterostructure containing vacancy defect displays superior optical performance compared to the pristine heterostructure across both the visible and ultraviolet regions. The electronic and optical properties of the heterostructure can be tuned through the introduction of vacancy defects. These theoretical findings are anticipated to offer a foundational framework for the design of ultraviolet photodetectors utilizing WSe2/GaN heterostructure.

Characterization of Sapropterin Dihydrochloride Tablet

Characterization of Kuvan tablets involved thorough analysis of physical, chemical, and dissolution properties. Formulation development encompassed pre-formulation studies, feasibility trials, and process optimization. Kuvan tablets demonstrated variability in sapropterin dihydrochloride concentration but rapid dissolution across different media. Consistent mechanical strength, low impurity levels, and appropriate pH values were observed, ensuring efficacy, safety, and reliability. Keywords: Sapropterin dihydrochloride, Hyperphenylalaninemia, Kuvan tablets

S-scheme heterojunction phthalocyanine/TiO2 photoelectrochemical sensor for innovative glutathione detection.

A novel photoelectrochemical sensor, employing an S-scheme heterojunction of phthalocyanine and TiO2 nanoparticles, has been developed to enable highly sensitive determination of glutathione. By integrating the favorable stability, environmental benignity, and electronic properties of the TiO2 matrix with the unique photoactivity of phthalocyanine species, the designed sensor presents a substantial linear dynamic range and a low detection limit for the quantification of glutathione. The sensitivity is attributed to efficient charge transfer and separation across the staggered heterojunction energy levels, which generates measurable photocurrent signals. Systematic variation of phthalocyanine content reveals an optimal composition that balances light harvesting capacity and electron-hole recombination rates. The incorporation of phosphotungstic acid (PTA) in sample preparation effectively minimizes interference from compounds like L-cysteine and others. Consequently, this leads to an improvement in accuracy through the reduction of impurity levels. Appreciable photocurrent enhancements are observed upon introduction of both oxidized and reduced glutathione at the optimized composite photoanode. Coupled with advantageous features of photoelectrochemical transduction such as simplicity, cost-effectiveness, and resistance to fouling, this sensor holds great promise for practical applications in complex biological media.

Evaluating Effectiveness of Multi-Component Waste Plastic Bags on Bitumen Properties: Physical, Rheological, and Aging.

This study examines the applicability of an unknown composition waste plastic bag sample as bitumen modifier. The waste components were initially characterized to identify the type of plastics and the level of impurity. Asphalt binder performance was examined for rutting, thermal, and age resistance. The results revealed that the waste plastic bags, predominantly consisted of Low-Density Polyethylene (LDPE) and Linear Low-Density Polyethylene (LLDPE) and contained 6.1% impurities. The binder tests indicated that the waste plastic bags enhanced the rutting resistance of bitumen by one grade, with its modification more similar to LLDPE, rather than LDPE. The thermal degradation and aging properties of the modified binders demonstrated that the bitumen modified by the waste plastic bags exhibited slightly lower resistance to temperature and aging compared to virgin LDPE and LLDPE. This was attributed to the impurities contained in the waste plastic. In conclusion, the analyzed waste plastic bags proved to be suitable for use in binder modification, presenting a viable alternative to virgin LLDPE.

A machine learning based prediction of reaction parameters on reaction kinetics for treatment of industrial wastewater

Industrial wastewater is a major cause of pollution of surface water bodies since it is often discharged into these water bodies without adequate treatment. Past attempts at treating industrial wastewater have led to the emergence of multiple approaches for the removal of impurities. These include conventional techniques like biological, physical, and chemical techniques, and recently advanced oxidation processes that have, under certain specific conditions, produced desired results through decomposing contaminating organic compounds into water, carbon dioxide, or less harmful molecules. This study examines the removal of phenol in industrial wastewater using a Photo-Fenton reagent on account of its cost-effectiveness and the possibility of rapid results. The effectiveness of the removal of contaminants was assessed based on the rate of reaction (k1). Data collected through laboratory experiments was then put through various Machine Learning classifiers including Neural Network, CHAID, Generalized Linear Model, Linear Classifier, and Random Trees using IBM SPSS Modeler and models trained. An accuracy of 97.2 % was observed for the Deep Neural Network. Further, it is observed that for a specific level of impurities in industrial water, the pH of solution, intensity of light, and amount of Hydrogen Peroxide (H2O2) are the most important factors in predicting the rate of reaction with concentration of [Fe3+] ions and catalyst TiO2 playing smaller roles.

Progress in Core-Shell Magnetic Mesoporous Materials for Enriching Post-Translationally Modified Peptides.

Endogenous peptides, particularly those with post-translational modifications, are increasingly being studied as biomarkers for diagnosing various diseases. However, they are weakly ionizable, have a low abundance in biological samples, and may be interfered with by high levels of proteins, peptides, and other macromolecular impurities, resulting in a high limit of detection and insufficient amounts of post-translationally modified peptides in real biological samples to be examined. Therefore, separation and enrichment are necessary before analyzing these biomarkers using mass spectrometry. Mesoporous materials have regular adjustable pores that can eliminate large proteins and impurities, and their large specific surface area can bind more target peptides, but this may result in the partial loss or destruction of target peptides during centrifugal separation. On the other hand, magnetic mesoporous materials can be used to separate the target using an external magnetic field, which improves the separation efficiency and yield. Core-shell magnetic mesoporous materials are widely utilized for peptide separation and enrichment due to their biocompatibility, efficient enrichment capability, and excellent recoverability. This paper provides a review of the latest progress in core-shell magnetic mesoporous materials for enriching glycopeptides and phosphopeptides and compares their enrichment performance with different types of functionalization methods.

The efficient synthesis of Pregabalin with impurity control using a continuous flow system

This article developed a microreactor system for the continuous synthesis of Pregabalin. Due to the exceptional heat transfer and mixing capabilities exhibited by the system at the microscale, the Hofmann rearrangement reaction, traditionally requiring multiple sequential steps in batch reactors, can now be efficiently achieved in a consolidated single-step microreactor process. The reaction was executed at a comparatively elevated temperature range of 40–50 °C, and took 5–6 min to achieve the yield of over 90 %, which was a significant improvement compared to the conventional batch reactor method, requiring 7–8 h with a yield of 83 %. The microreactor system utilized its excellent mass and heat transfer performance to reduce the level of the key impurity to below 0.15 % at higher reaction temperatures, meeting the quality requirements for pharmaceutical production. Through experimental research, we determined the effects of reaction conditions like concentration, temperature, and residence time on the reaction rate, as well as key trace impurities.

Biotemplated Fe/La-co-doped TiO2 for photocatalytic depth treatment of compressed leachate from refuse transfer station.

Compressed leachate is a contaminated liquid containing various organic and inorganic pollutants produced in municipal refuse transfer stations, which pollute soil and groundwater, posing serious risks to the environment and human health. The Environmental Technology Co., Ltd. (Shenzhen, Guangdong Province, South China) treated compressed leachate obtained from a refuse transfer station. The chemical oxygen demand (COD) (641.2mg/L) of treated compressed leachate did not meet the wastewater quality standards in China for discharge into municipal sewers (COD ≤ 500mg/L) and the company's design discharge requirements (COD ≤ 400mg/L). Therefore, their further in-depth treatment is necessary. To this end, waste tobacco leaves were used as the biotemplate herein, and Fe/La-co-doped TiO2 (xFe,yLa)-TTiO2(g) was synthesized using a solvothermal-assisted biotemplating method. The photocatalytic depth treatment of compressed leachate was performed under simulated solar light using the prepared catalysts. After (3Fe,3La)-TTiO2(g) treatment, the COD of the leachate decreased from 641.2 to 280.1mg/L, and the COD removal rate was 1.2, 1.1, and 1.6 times higher than that of pure Fe-doped, La-doped and non-biological template TiO2, respectively. Characterization confirmed that the biological template endowed the catalyst with a unique morphology and high specific surface area. Its rich activity sites are conducive to enhancing the adsorption capacity of pollutants and providing an ideal place for photocatalytic reactions. Co-doping with iron and lanthanum ions altered the band structure of TiO2 and promoted the interconversion of Fe3+/Fe2+ and La3+/La2+ during photocatalysis. First-principles density functional theory simulations demonstrated that co-doping Fe and La in TiO2 created impurity levels that facilitated the transfer of photogenerated electrons. This study provides a new purification pathway for the depth treatment of compressed leachate.

Oxygen vacancy and Ce ion co-synergize to enhance the photocatalytic degradation performance of FeTiO3: An experimental and DFT study

Doping the iron titanate (FeTiO3) with rare earth element is considered as an effective method of enhancing its photocatalytic performance. In this work, the novel FeTiO3 doped with cerium (Ce) (Ce/FeTiO3) photocatalysts were designed and synthesized using the sol–gel method. The 10 mol% Ce/FeTiO3 photocatalyst displays excellent photocatalytic performance for degrading the tetracycline hydrochloride (TCH), methylene blue (MB) and brilliant blue (BB). The degradation efficiencies are 97.50 % (TCH), 95.40 % (MB), and 84.60 % (BB), respectively, and the degradation rate constants (k) are 3.68, 2.91, and 7.12 times that of pure FeTiO3. Density functional theory (DFT) calculations were used to study the photocatalytic degradation mechanism in depth. The results show that the content of oxygen vacancy is increased and the oxygen vacancy formation energy is significantly increased from 2.25 eV to 6.97 eV after doping the Ce ion, which can provide more active sites to degrade pollutants and enhance the photocatalytic performance of the FeTiO3. Furthermore, the Ce 4f orbital can narrow the bandgap and form the impurity level to capture the photoexcited electron, inhibiting the recombination rate of photocarriers in FeTiO3. This work is expected to provide a valuable insight into the Ce doped FeTiO3 photocatalyst, which is conductive to expanding the practical applications of FeTiO3-based photocatalyst.