Journal of Applied Spectroscopy最新文献

Based on a comparison of experimental and theoretical IR spectra of six brassinosteroids with different configurations of the (22,23)-diol group and the substituent at C-24, criteria are proposed for rapid discrimination between the (22R,23R)- and (22S,23S)-stereoisomers. These criteria are validated by a combined molecular mechanics and CNDO/2 calculation and are found suitable for express screening of synthesized compounds and checking their stereochemical purity without recourse to time-consuming techniques.

A simple and accurate spectrophotometric method was developed for the simultaneous determination of levodopa (LD), carbidopa (CD), and entacapone (ENT) in pharmaceutical formulations. Because of the extensive overlap among their absorption spectra, three chemometric techniques — Artificial Neural Network (ANN), Fuzzy Inference System (FIS), and Adaptive Neuro-Fuzzy Inference System (ANFIS) — were applied to extract quantitative information and resolve spectral interferences. The ANN model, optimized using the Levenberg–Marquardt (LM) algorithm, demonstrated excellent predictive performance, with a coefficient of determination (R²) of 0.9999 for all analytes. The corresponding mean recoveries were 100.25, 99.42, and 99.65%, and the root mean square error (RMSE) values were 0.02, 0.006, and 0.05 for LD, CD, and ENT, respectively. The FIS model produced R² values of 0.9996 (LD and ENT) and 0.9998 (CD), with mean recoveries of 99.06, 99.42, and 99.25% and RMSE values of 0.14, 0.018, and 0.13, respectively. The ANFIS model yielded R² values of 0.9981, 0.9970, and 0.9983, mean recoveries of 99.09, 98.56, and 99.34%, and RMSE values of 0.19, 0.05, and 0.22 for LD, CD, and ENT, respectively. Statistical comparison with a reference high-performance liquid chromatography (HPLC) method using one-way analysis of variance (ANOVA) indicated no significant difference between the results (p > 0.05). These findings demonstrate that the proposed spectrophotometric-chemometric approaches provide reliable and cost-effective alternatives to chromatographic techniques for the routine quality control of multicomponent pharmaceutical formulations.

A simple, accurate, and precise spectrophotometric method has been developed for the simultaneous determination of pseudoephedrine (PSE) and loratadine (LOR) in bulk and tablets. The method principally exploits the spectral characteristics of the two compounds to affect mathematical manipulation of Beer’s law. The approach in this method enabled the removal of the spectral interference from LOR at the wavelength for the determination of PSE. It was possible to determine pseudoephedrine in the presence of loratadine using two wavelengths (257 and 280 nm). Two calibration curves were established for the analysis. The first was constructed to quantify LOR in the mixture on the basis of its absorbance at 280 nm. The second calibration curve was developed to determine the concentration ratio (CR) between the components at 257 nm. This curve was obtained by plotting the absorbance ratio (AR) against the concentration ratio, defined as CR = [PSE]/[LOR]. The concentration of PSE was calculated using the equation: [PSE] = CR_EXP × [LOR]. The developed analytical method was statistically validated in accordance with ICH Q2 guidelines and yielded satisfactory results. The assay results, expressed as a percentage of the labeled claim, were found to be 99.97 ± 0.71% and 101.10 ± 1.32% for PSE and LOR, respectively. These findings demonstrate that the proposed method is suitable for routine quality control analysis of tablet formulations. The validity of the proposed method was confirmed through statistical comparison of the data with those obtained by a reference chromatographic method.

Aquilaria malaccensis, a highly endangered species valued for its fragrant resin, faces significant threats from over-harvesting. This study presents a conservation-oriented method for producing agarwood metabolites using a standardized in vitro callus proliferation protocol and solvent-based FTIR spectral profiling. FTIR analysis identified functional groups in ethanol, methanol, ethyl acetate, acetone, and petroleum ether extracts from both in vivo plants and in vitro callus. Callus extracts exhibited higher intensity and a greater diversity of sesquiterpenoidrelated functional groups. Ethanolic and methanolic extracts from both sources exhibited strong O–H and N–H stretches (3366 and 3400 cm^–1), while callus extracts displayed unique peaks such as C=O (1076 cm^–1), C=N (1076 cm^–1), and C=C=C (1956 cm^–1), indicating oxidized and nitrogenous sesquiterpenoids. Ethyl acetate and petroleum ether extracts demonstrated strong C–H stretching and bending vibrations at 2920, 1460, and 778 cm^–1, characteristic of long hydrocarbon chains in resinous compounds. Notably, ethyl acetate extracts from callus also indicated nitrogenous and aromatic sesquiterpenoids. Acetone extracts revealed aromatic and aminerelated peaks at 1509, 1400, and 1056 cm^–1. These findings highlight the enhanced biosynthetic potential of callus cultures. This approach reduces reliance on wild populations, preserves the product's biochemical integrity, and offers an eco-friendly alternative for pharmaceutical applications.

We aimed to develop a stability-indicating method for tenofovir disoproxil using first-order derivative UV spectrophotometry to achieve clearer separation of overlapping spectra and ensure reliable detection of the drug along with its degradation products. λ_max was recorded at 231 nm, while the first-order derivative wavelength was selected at 244 nm. The method followed Beer–Lambert's law in the concentration range of 35–60 μg/mL with an R² = 0.9961, and methanol proved to be the most suitable solvent. The method was validated as per ICH Q2 (R2) guidelines, covering linearity, accuracy, precision, LOD, LOQ, and robustness. The results showed minimal variation, with RSD values below 2%, and a recovery range of 98–101%, confirming the method's accuracy. Forced degradation studies under different stress conditions further demonstrated the stability of tenofovir disoproxil, supporting its reliability during formulation and market release. Thus, the method provides a dependable, precise, and economical analytical strategy for assessing the stability profile of tenofovir disoproxil and identifying its degradation products.

This paper deals with the birefringence and order parameter calculation of liquid crystalline (LC) materials like p-n-decyloxy (10OBA) benzoic acid with the incorporation of ZnO nanoparticles (NPs) in different low wt.% concentrations (0.5–2 wt.%). From the characterization techniques, it is evident that ZnO NPs in 10OBA results in significant changes in optical properties such as refractive index (RI), birefringence (δn) and order parameter (S). The observations suggest that, because of their larger size and higher dipole moments compared to the nematic LC molecules, ZnO NPs generate a higher torque. This torque facilitates the orientation of the LC molecules, leading to increased birefringence and improved ordering within the LC system. The order parameter values are calculated using four optical methods — Kuczynksi, Haller, Effective geometry, and Vuks — at a stabilized nematic region in the visible range at 435, 500, 570, and 635 nm wavelengths. The values of dispersive powers are also increased for the 10OBA with ZnO NPs in various concentrations. The results suggest that the materials can be used in liquid crystal displays and tunable lenses.

Enhancing the precision of quantitative analysis in calibration-free laser-induced breakdown spectroscopy (CFLIBS) requires a thorough understanding of self-absorption correction techniques. This work introduces blackbody radiation referenced-particle swarm optimization (BRR-PSO) as a self-absorption correction technique. This method compares the measured spectral intensity to blackbody radiation using Particle Swarm Optimization (PSO) to enable quick self-absorption correction. Corrected spectral intensities are obtained by iteratively refining initial values using the PSO optimization technique. Experiments were conducted on alloy samples to verify the efficacy of this method. The results show that as compared to the traditional CF-LIBS methodology, the CF-LIBS with the BRR-PSO method significantly improves the mean relative error (MRE). The MRE decreased from a range of ~27.35–43.75% to ~5.14–7.86% for the six alloy samples. For Fe I, Mn I, Cr I, Mo I, C I, and Si I, the Boltzmann plot linear fi t coefficient of determination (R²) increased from 0.9220, 0.8050, 0.8801, 0.7102, 0.9064, and 0.9146 to 0.9887, 0.9813, 0.9662, 0.9809, 0.9542, and 0.9459, respectively. By greatly increasing both quantitative analysis accuracy and adaptability, the CF-LIBS approach improved with BRR-PSO demonstrating a clear advantage over conventional CF-LIBS. This development makes CF-LIBS technology more dependable and adaptable for real-world analysis, which is crucial for extending its useful applications.

This study systematically investigates the effects of configuration interaction (CI) on the photoionization of the 3s shell in argon atoms using relativistic multiconfiguration Dirac–Fock methods. To quantify both CI effects and electron correlations, four distinct computational models were employed: Model A (single-configuration), Model B (restricted configuration with valence excitations up to the 4p orbital), Model C (extended configuration with core–valence excitations up to the 4p orbital), and Model D (extended configuration with core–valence excitation up to the 4d orbital). The results demonstrate that Models C and D, which incorporate single and double excitations from core–valence electrons into the 4p and 4d orbitals, achieve excellent agreement with the experimental cross-sectional data. Notably, the angular asymmetry-parameter β exhibits pronounced energy-dependent behavior, with significant divergence observed between models employing restricted versus extended CI treatments. A detailed analysis was conducted to explore the variations in bound-state and continuum-state electron orbitals across different models, as well as their influence on the photoionization transition matrix elements. This work underscores the critical importance of accurately modeling core–valence electron correlations for reproducing both absolute cross sections and photoelectron angular distributions, particularly near ionization thresholds and the Cooper minimum. These findings provide valuable insights into the fundamental mechanisms governing photoionization processes and highlight the need for advanced theoretical frameworks to enable precise predictions in atomic collision dynamics.

Triazoxide as a fungicide was experimentally characterized via the help of the FTIR, ¹H/¹³C NMR chemical shifts and UV-Vis spectroscopies. Theoretical modeling was performed using the DFT/B3LYP/6-311++G(df,pd) computational level. The correlation between experimental and computed spectral data was investigated. The conformational analysis was used to obtain the most stable molecular geometry. Computational studies were performed for the two most stable conformational forms (C1 and C2) of triazoxide. The vibrational frequencies and assignments helped to determine the molecular vibrational motions. The effect of electron delocalization within the π-systems of triazoxide on its molecular structure and some vibrational wavenumbers was uncovered. The computational NMR results were analyzed with the GIAO method. The intra-molecular electronic transitions corresponding to the UV-Vis wavelengths were elucidated with simulations of the HOMO/LUMO electron localizations. The electron densities within the occupied/unoccupied molecular orbitals were investigated with the density of states analysis.

Feasibility is demonstrated for obtaining a dielectric material derived from oxidized porous silicon and titanium oxide by depositing the latter onto porous silicon using a sol-gel method followed by high-temperature oxidation. The resulting dielectric material has an enhanced refractive index, making it promising for creating low-loss integrated optical channel waveguides in bulk microassemblies of electronic circuits with optical interconnects.