Journal of Applied Spectroscopy最新文献

The atmospheric wind field in the troposphere and stratosphere notably impacts human production and life. The lidar is one of the most effective means of detecting the atmosphere in this region due to its high resolution and sensitivity. To meet this need, aerosol and molecular backscattering signals of different wavelengths were analyzed via lidar technology. The results showed that the 355-nm laser provides an advantage in detecting the atmosphere under clear weather conditions, and the 1064-nm laser achieves superior detection performance under severe haze weather conditions, while the detection performance of the 532-nm laser varies between those of the other lasers. The detection performance of the system was simulated using a 532-nm laser, and the maximum detection height reached 43 km under clear weather conditions and 28 km under polluted weather conditions. This analysis provides support for obtaining atmospheric wind fields in the troposphere and stratosphere under all weather conditions in the future.

The present work describes the development and validation of zero-order derivative and first-order derivative UV-Vis spectrophotometric methods for the quantitative determination of viloxazine hydrochloride. The spectrophotometric determination was performed within 200–400 nm and the first-order derivative spectrum was obtained by comparing absorbance to wavelength. The developed method was validated under ICH guidelines for linearity, precision, accuracy, limits of detection and quantification, and robustness. The correlation coefficient value of the methods was 0.9989 (method A) and 0.9979 (method B) with a limit of detection of 3 μg/mL and a limit of quantification of 9 μg/mL. The precision of the methods was confirmed by calculating the %relative standard deviation, which is acceptable as per guidelines. The accuracy of the methods was calculated and represented in terms of % mean recovery. Moreover, the greenness profiles of the developed UV method were assessed using the green analytical procedure index (GAPI) and the AGREE evaluation method. The results revealed adherence of the described method to the green analytical chemistry principles. We successfully developed and validated the UV method according to ICH guidelines. The method was proved for the analysis of marketed formulations.

Folic acid (FA) is an important nutrient for several physiological functions, including DNA synthesis, amino acid homeostasis, and normal blood production. With the increased circulation of counterfeit and substandard drugs worldwide, it is vital to ensure the quality of the FA tablets using a simple and validated analytical method that can be applied for routine QC of FA tablets in developing countries or worldwide. We developed two validated spectrophotometric methods for the quantitation of FA in tablet dosage forms. The developed methods were applied to bulk and FA powdered tablets dissolved in alkaline media using a 0.1 N NaHCO₃ solution (method 1) and a 0.1 N NaHCO₃/0.1N HCl solution (method 2). The established wave lengths λ_max were found to be at 256, 283, and 366 nm (method 1) and at 295 nm (method 2). Method validation parameters included linearity, accuracy, precision, LOD, and LOQ. The accuracy and precision (RSD%) of the methods were tested by direct sample/standard comparison (n = 5) and found to be simple, selective, and robust. Good linearity was achieved, with correlation coefficients ≥0.9923 and limits of detection and quantification ranging from 1.46 to 2.44 μg/mL and from 4.45 to 7.38 μg/mL at 256, 283, and 366 nm (method 1). Likewise, the LOD and LOQ values of method 2 were 1.53 and 4.66 μg/mL, respectively. The assay results for FA tablets were 102–107% for method 1, with RSD% between 3.73 and 7.75%. For method 2, the assay results for FA tablets were 106.54 ± 2.34% with a linearity of 0.9998. These developed methods provide a simple alternative to the important published methods for assaying of FA in tablet formulations.

Dy³⁺- and Sm³⁺-doped Na₂Al₂B₂O₇ phosphors were synthesized at 850°C for 6 h in air. The phase analyses of all prepared borates were carried out using powder X-ray diffraction (XRD). A spectrofluorometer was used to examine the photoluminescence (PL) characteristics of the prepared phosphors at room temperature. When excited at 350 nm, Na₂Al₂B₂O₇:Dy³⁺ radiates at 481–491, 575–583, and 673 nm. After being excited at 402 nm, Na₂Al₂B₂O₇:Sm³⁺ radiates at 561, 603, 650, and 709 nm. As a result of this study, two new optical materials that emit light in the visible region were prepared.

The widespread use of pesticides poses many potential risks to food safety and human health. Thus, rapid and accurate detection methods for pesticide residues need to be established. In this study, ultraviolet (UV) spectroscopy coupled with support vector regression and variable selection methods was used to quantitatively detect the content of imidacloprid in apple juice. First, the UV spectra of diff erent imidacloprid concentrations in apple juice were collected, and the acquired spectra were preprocessed by Savitzky–Golay smoothing. Then, the feature variables were selected by the variable iterative space shrinkage approach (VISSA), iteratively retains informative variables (IRIV), and random frog (RF) algorithms. Finally, particle swarm optimization support vector regression (PSOSVR) prediction models based on the feature variables and the full-spectrum variables were established to detect imidacloprid in apple juice. The results showed that the VISSA–PSO-SVR model had the optimal predictive performance, the determination coefficient of the prediction set (R_p²) was 0.99933, and the root mean square error of the prediction set (RMSEP) was 0.0894 mg/L. The results from this study indicated that the combination of UV spectroscopy and the VISSA–PSO-SVR model could be used for the quantitative detection of imidacloprid in apple juice.

The effects of pH and the solution composition on the photophysical properties of two carboxyfluorescein bifluorophores were studied along with a comparison of the fluorescence effect of these bifluorophores with that of monomer carboxyfluoresceins (5-FAM and 6-FAM) in conjugates with protein molecules. Both the bifluorophores were found to fluoresce well in an alkaline medium but the fluorescence intensity decreased at pH 6–7 and almost disappeared in acidic media. The fluorescence of meta-(6-FAM)₂ is very sensitive to the solution composition, while the fluorescence of meta-(5-FAM)₂ is more stable and depends only slightly on the solution properties. Upon formation of a conjugate of the bifluorophore with a protein, the fluorescence yield of the bifluorophore decreases to a greater extent in comparison with the FAM monomers but the total fluorescence yield is not less than the intensities of the two carboxyfluorescein monomer–protein conjugates due to the high extinction coefficient of the bifluorophore (~140,000 M^–1·cm^–1).

Based on the method of photo-orientation of the azo-dye AtA-2, an electrically controlled Fresnel lens has been developed which is a microstructured liquid crystal element made up of alternating rings with twist- and planar orientations of the liquid crystal director. It is shown that the use of a control voltage makes it possible to control the efficiency of the focusing of laser radiation, as well as to turn off the lens. An optimum control voltage (~3 V) is determined at which a maximum focal efficiency and satisfactory quality of image construction over a wide spectral range from 530 nm to 1.1 μm are attained.

An innovative, meticulously crafted, targeted, expeditious, precise, and cost-effective methodology was pioneered utilizing UV-Vis spectrophotometry for the quantitative determination of Mirabegron in both its pristine state and pharmaceutical tablet formulation. Following thorough deliberation on factors such as solubility, stability, toxicity, and carcinogenicity, petroleum ether emerged as the solvent of choice, aligning with the principles of environmentally conscious methodology. The absorption maxima were unequivocally detected at a wavelength of 250 nm, making petroleum ether the solvent of choice. The method adheres faithfully to Beer's law within a concentration range spanning from 0.004 to 0.016 mg/mL, boasting a remarkable correlation coefficient of 0.9945. LOD and LOQ were meticulously computed from the dataset, yielding values of 0.0001663 and 0.0005039, respectively. The relative standard deviation, meticulously derived from the dataset, stands at less than 2%. Moreover, in the rigorous accuracy assessment, Mirabegron's recovery percentage fell impressively within the narrow band of 98.62 to 101.46%. During both the intraday and interday precision evaluations, the %Assay remained consistently within the stringent range of 99.63 to 101.12%, affirming the method's precision. Furthermore, adherence to the rigorous guidelines outlined in ICH Q2 (R1) was ensured throughout the comprehensive validation process, consolidating the method's credibility and suitability for analytical applications.

Parallel factor analysis (PARAFAC) is widely used in relation to fluorescence excitation/emission spectra to track the movement of water masses and to study seasonal changes in the composition and content of dissolved organic matter. The stage of selecting the number of components is one of the most difficult when using factor analysis. The widely used method of analyzing loads when splitting the original set into halves in many cases does not allow a determination of the best model because of the closeness of their statistical estimates. Because the use of regularization with a penalty for the sum of parameter modules tends to lead to sparse solutions in which some of the coefficients are equal to zero, the use of this approach allows one to select those variables that carry useful information. A procedure is proposed for selecting the number of components when performing parallel factor analysis of fluorescence spectra using a penalty for the 1- and 2-norms of the solution.

STACK family borates are promising compounds for optical applications. Synthesis and luminescence of Sr₃Y(BO₃)₃ borate belonging to the STACK family is described. Trivalent activators Tb³⁺ and Gd³⁺ occupy yttrium sites. Owing to fixed, well-separated positions (Y–Y distance 7.396 Å), a large concentration of Gd³⁺, as much as 50% relative to Y, could be accommodated without causing concentration quenching. In the case of Gd³⁺, both excitation and emission lines arise in f–f transitions. Photoluminescence emission is obtained in UV regions. In the case of Tb³⁺, concentration quenching was observed above 2%. Prominent excitation of Tb³⁺ is in the form of a band arising in the f–d-type transition, while emission comes from f–f transitions. Emission lifetimes are of the order of milliseconds, typically forbidden f–f transitions.