Hasil untuk "Analytical chemistry"

Shaojun Guo, S. Dong

R. Tsao

Polyphenols are the biggest group of phytochemicals, and many of them have been found in plant-based foods. Polyphenol-rich diets have been linked to many health benefits. This paper is intended to review the chemistry and biochemistry of polyphenols as related to classification, extraction, separation and analytical methods, their occurrence and biosynthesis in plants, and the biological activities and implications in human health. The discussions are focused on important and most recent advances in the above aspects, and challenges are identified for future research.

G. Ulrich, R. Ziessel, A. Harriman

B. Finlayson‐Pitts, J. Pitts

H. Zollinger

C. Burtis

Ivan S. Ufimtsev, T. Martínez

Qiming Sun, Matthew R Hermes, Xiaojie Wu et al.

Over the past decade, the Python-based Simulations of Chemistry Framework (PySCF) has developed into a widely used open-source platform for electronic structure theory and quantum chemical method development. This article reviews the major advances since the previous overview in 2020, covering new modules and methodology, infrastructure changes, and performance benchmarks.

Shweta Annaldasula, Nilu Bhadani, Izaz Shaik et al.

Objective: This systematic review intended to compare the influence of “laser-activated irrigation (LAI)” and “ultrasonic irrigation (UI)” on postoperative pain following root canal treatment in human subjects. Materials and Methods: A comprehensive literature search was conducted in PubMed, Scopus, Cochrane Library, and Web of Science up to April 2025. “Randomized clinical trials (RCTs)” comparing LAI and UI in terms of postoperative pain outcomes were included. Studies evaluating pain using validated scales such as the “Visual Analog Scale (VAS)” within the first seven days post-treatment were considered. Results: Seven RCTs met the inclusion criteria. Most studies demonstrated that LAI, particularly using Er: YAG-based techniques (e.g. Photon-Induced Photoacoustic Streaming [PIPS], Shock Wave Enhanced Emission Photoacoustic Streaming [SWEEPS]), resulted in significantly lower postoperative pain during the first 24–48 h compared with UI. However, pain levels between the groups generally equalized by 72 h. Analgesic consumption was comparable in both groups across most studies. Conclusion: LAI may offer a modest advantage over ultrasonic activation in reducing early postoperative pain after root canal therapy. Both methods, however, are effective and superior to conventional irrigation in pain reduction.

Irene Romero-Alfano, Violeta Martínez, Nathaly Peña et al.

This study presents a comprehensive evaluation and environmental risk assessment (ERA) of pharmaceutical residues in the Cerrón Grande Reservoir, one of the most important surface water bodies in El Salvador. Sampling campaigns were conducted over a one-year period, covering both the dry (January 2024) and rainy (July 2024) seasons. A total of 76 pharmaceutical compounds were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS), of which only five were not detected. During the dry season, the highest environmental concentrations were observed for mecamylamine (1710–6913 µg L⁻¹), 1,7-dimethylxanthine (379–2829 µg L⁻¹), chloroquine (2.29–362.7 µg L⁻¹), and hydroxychloroquine (5.02–315.4 µg L⁻¹). Concentrations generally decreased in the rainy season, with mecamylamine (1526–2198 µg L⁻¹), 1,7-dimethylxanthine (0.018–0.55 µg L⁻¹), and caffeine (0.2–0.474 µg L⁻¹) remaining the most prevalent. Compounds exceeding 1 µg L⁻¹ were assessed using predicted no-effect concentrations (PNEC) to calculate risk quotients (RQ). Chloroquine (RQ = 3346.3), mecamylamine (RQ = 1437.8), hydroxychloroquine (RQ = 1027.2), and manidipine (RQ = 271.0) posed the highest risks during the dry season, while only mecamylamine (RQ = 502.0) exceeded this threshold in the rainy season. To our knowledge, this represents the first in-depth study of pharmaceutical residues in Salvadoran surface waters, providing a foundational reference for future research and environmental policy in the region.

Xiaofeng Ma, Rui Sun, Jinghui Cheng et al.

Amer Alrakik, Gian Luigi Bendazzoli, Stefano Evangelisti et al.

We present a general theory to treat periodic solids with quantum-chemistry methods. It relies on two main developments: 1) the modeling of a solid as a Clifford torus which is a torus that is both periodic and flat and 2) the introduction of a periodic gaussian basis set that is compatible with the topology of the Clifford torus. We illustrate our approach by calculating the ground-state energy of a periodic chain of hydrogen atoms within both Hartree-Fock and coupled cluster theory. We demonstrate that our approach yields the correct ground-state energy in the thermodynamic limit by comparing it to the ground-state energy of a ring of hydrogen atoms in the same limit. Since equivalent ring-like calculations for three-dimensional solids are impossible, our approach is an excellent alternative to perform quantum-chemistry calculations of solids. Our Clifford formalism can be seamlessly combined with current implementations of quantum-chemistry methods designed for atoms and molecules to make them applicable to solids.

Charles J. Law, Romane Le Gal, Karin I. Öberg et al.

The sulfur chemistry in protoplanetary disks influences the properties of nascent planets, including potential habitability. Although the inventory of sulfur molecules in disks has gradually increased over the last decade, CS is still the most commonly-observed sulfur-bearing species and it is expected to be the dominant gas-phase sulfur carrier beyond the water snowline. Despite this, few dedicated multi-line observations exist, and thus the typical disk CS chemistry is not well constrained. Moreover, it is unclear how that chemistry - and in turn, the bulk volatile sulfur reservoir - varies with stellar and disk properties. Here, we present the largest survey of CS to date, combining both new and archival observations from ALMA, SMA, and NOEMA of 12 planet-forming disks, covering a range of stellar spectral types and dust morphologies. Using these data, we derived disk-integrated CS gas excitation conditions in each source. Overall, CS chemistry appears similar across our sample with rotational temperatures of ${\approx}$10-40 K and column densities between 10$^{12}$-10$^{13}$ cm$^{-2}$. CS column densities do not show strong trends with most source properties, which broadly suggests that CS chemistry is not highly sensitive to disk structure or stellar characteristics. We do, however, identify a positive correlation between stellar X-ray luminosity and CS column density, which indicates that the dominant CS formation pathway is likely via ion-neutral reactions in the upper disk layers, where X-ray-enhanced S$^+$ and C$^+$ drive abundant CS production. Thus, using CS as a tracer of gas-phase sulfur abundance requires a nuanced approach that accounts for its emitting region and dependence on X-ray luminosity.

Sarah Marie Lößlein, Rolf Merz, Yerila Rodríguez-Martínez et al.

To understand the complex interplay of topography and surface chemistry in wetting, fundamental studies investigating both parameters are needed. Due to the sensitivity of wetting to miniscule changes in one of the parameters it is imperative to precisely control the experimental approach. A profound understanding of their influence on wetting facilitates a tailored design of surfaces with unique functionality. We present a multi-step study: The influence of surface chemistry is analyzed by determining the adsorption of volatile carbonous species (A) and by sputter deposition of metallic copper and copper oxides on flat copper substrates (B). A precise surface topography is created by laser processing. Isotropic topography is created by ps laser processing (C), and hierarchical anisotropic line patterns are produced by direct laser interference patterning (DLIP) with different pulse durations (D). Our results reveal that the long-term wetting response of polished copper surfaces stabilizes with time despite ongoing accumulation of hydrocarbons and is dominated by this adsorption layer over the oxide state of the substrate (Cu, CuO, Cu2O). The surfaces' wetting response can be precisely tuned by tailoring the topography via laser processing. The sub-pattern morphology of primary line-like patterns showed great impact on the static contact angle, wetting anisotropy, and water adhesion. An increased roughness inside the pattern valleys combined with a minor roughness on the peaks favors air-inclusions, isotropic hydrophobicity, and low water adhesion. Increasing the aspect ratio showed to enhance air-inclusions and hydrophobicity despite increased peak roughness while time dependent wetting transitions were observed.

Aidan Pellow-Jarman, Shane McFarthing, Doo Hyung Kang et al.

A novel hybrid quantum-classical approach has been developed to efficiently address the multireference quantum chemistry problem. The Handover Iterative Variational Quantum Eigensolver (HiVQE) is designed to accurately estimate ground-state wavefunctions by leveraging both quantum and classical computing resources. In this framework, noisy intermediate-scale quantum (NISQ) hardwares efficiently explore electron configurations, while classical computers compute the corresponding wavefunction without the effect of noise of NISQ computer, ensuring both accuracy and computational efficiency. By generating compact yet chemically accurate wavefunctions, HiVQE advances quantum chemistry simulations and facilitates the discovery of novel materials. This approach demonstrates significant potential for overcoming the limitations of classical methods in strongly correlated electronic systems.

Maja Biočić Šormaz, Tomislav Kraljević, Lea Kukoč-Modun

N-acetyl-L-cysteine (NAC) is a precursor of glutathione and a natural antioxidant. It is used to treat paracetamol overdose and to dissolve thick bronchial mucus. A novel, simple, reproducible, and rapid kinetic spectrophotometric method for determining NAC in pharmaceutical formulations is proposed. The method is based on a redox reaction where NAC reduces bis(bathocuproinedisulfonate)cuprate(II), forming a yellow-orange complex of bis(bathocuproinedisulfonate)cuprate(I). The resulting stable complex exhibited maximum absorbance at λ = 483 nm. Under optimised chemical reaction parameters, both the fixed-time and initial-rate methods were used to generate calibration curves. For the fixed-time method, the curve was linear in the concentration range of 3.0 · 10−7 to 7.0 · 10−5 mol l−1, with the equation y = 13140x − 0.0005 and a coefficient of determination of R2= 0.9999. For the initial-rate method, the curve was linear in the concentration range of 7.0 · 10−7 to 7.0 · 10−5 mol l−1 with the equation y = 1.040x + 3.220 and R2 = 0.9991. The slope of the logarithmic form of the calibration curve (1.040) for the initial-rate method confirmed the pseudo-first order nature of the reaction. The proposed method was successfully applied for the determination of NAC in commercial pharmaceutical preparations, yielding results comparable to those obtained using the recommended method according to the pharmacopoeia.

Yifei Zhu, Mengge Li, Chao Xu et al.

Due to rapid advancements in deep learning techniques, the demand for large-volume high-quality databases grows significantly in chemical research. We developed a quantum-chemistry database that includes 443,106 small organic molecules with sizes up to 10 heavy atoms including carbon (C), nitrogen (N), oxygen (O), and fluorine (F). Ground-state geometry optimizations and frequency calculations of all compounds were performed at the B3LYP/6-31G* level with the BJD3 dispersion correction, while the excited-state single-point calculations were conducted at the $ω$B97X-D/6-31G* level. Totally twenty seven molecular properties, such as geometric, thermodynamic, electronic and energetic properties, were gathered from these calculations. Meanwhile, we also established a comprehensive protocol for the construction of a high-volume quantum-chemistry database. Our QCDGE (Quantum Chemistry Database with Ground- and Excited-State Properties) database contains a substantial volume of data, exhibits high chemical diversity, and most importantly includes excited-state information. This database, along with its construction protocol, is expected to have a significant impact on the broad applications of machine learning studies across different fields of chemistry, especially in the area of excited-state research.

Steven C. Pan, Jia Yi Han, Fun Man Fung

Prequestioning is an instructional strategy that involves taking practice tests on to-be-learned information followed by studying the correct answers. Despite promising results in laboratory studies, it has rarely been examined in authentic educational settings. The current study investigated the pedagogical benefits of prequestioning as a learning intervention in an undergraduate environmental chemistry course. In each of 10 lecture sessions, the course lecturer administered four prequestions targeting concepts that were to be taught in the very next lecture session, then presented the correct answers. On assessments occurring during the next lecture session, there was evidence of a prequestioning effect, that is, better performance on questions targeting prequestioned concepts versus non-prequestioned concepts, in most cases. That benefit of prequestioning, which was relatively large (across all lecture sessions, an overall effect size of Cohens d = 2.04, p < .001), highlights the utility of prequestioning as a promising approach for enhancing learning in undergraduate chemistry and similar courses.

Haochen Zhao, Xiangru Tang, Ziran Yang et al.

The advancement and extensive application of large language models (LLMs) have been remarkable, including their use in scientific research assistance. However, these models often generate scientifically incorrect or unsafe responses, and in some cases, they may encourage users to engage in dangerous behavior. To address this issue in the field of chemistry, we introduce ChemSafetyBench, a benchmark designed to evaluate the accuracy and safety of LLM responses. ChemSafetyBench encompasses three key tasks: querying chemical properties, assessing the legality of chemical uses, and describing synthesis methods, each requiring increasingly deeper chemical knowledge. Our dataset has more than 30K samples across various chemical materials. We incorporate handcrafted templates and advanced jailbreaking scenarios to enhance task diversity. Our automated evaluation framework thoroughly assesses the safety, accuracy, and appropriateness of LLM responses. Extensive experiments with state-of-the-art LLMs reveal notable strengths and critical vulnerabilities, underscoring the need for robust safety measures. ChemSafetyBench aims to be a pivotal tool in developing safer AI technologies in chemistry. Our code and dataset are available at https://github.com/HaochenZhao/SafeAgent4Chem. Warning: this paper contains discussions on the synthesis of controlled chemicals using AI models.

Roberta La Tella, Danilo Donnarumma, Francesca Rigano et al.

The present research focused on the use of high temperatures to achieve fast separations in Liquid Chromatography (LC) and minimize the consumption of organic solvents. Particularly, superheated water was employed, by exploiting the decrease in dielectric constant of water when increasing the temperature. To realize this kind of application, the availability of LC columns resistant at high temperature is mandatory. Recently, porous graphitic carbon (PGC) columns have been proposed as stationary phases resistant up to 250 °C. Hardware modifications were also necessary to guarantee the efficient heating of the mobile phase prior of entering the column, as well as its rapid cooling before detection by photodiode array (PDA). Specifically, an LC system was interfaced to a GC oven, which hosted the LC column; to achieve a fast and efficient heating of the eluent coming from the autosampler prior to enter into the column, a pre-heating tube was interposed between the autosampler outlet and the column inlet. Instead, a cooling loop was connected between the column outlet and the PDA cell. A mixture of 1-nitroalkanes was used to evaluate the performance of the system in terms of dead volumes, band broadening and peak shape, as well as chromatographic efficiency and resolution. The use of higher temperatures allowed to perform analyses at higher flow rates in reduced analysis time and was also in terms of peak bandwidth resulting to increased efficiency for the most retained compound. Moreover, van't Hoff plots were obtained at different temperature, confirming that the most retained analyte greatly benefited of the temperature increase.The system was applied to the analysis of parabens in cosmetic and food products. The method combined eco-sustainable sample preparation with high-temperature LC separation on a PGC column and was fully validated in terms of linearity, precision, accuracy and detection and quantification limits. The developed method was critically evaluated by comparing the output of different metric tools implemented in the last decade for the quantitative assessment of the greenness.