Here we present an experiment on ghost imaging with a pseudo-thermal light source and a single-photon detector array. In the experiment, the light intensity is taken to be so low that the photon detection rate is comparable to the dark counts rate. To minimize the influence of dark counts on the ghost image (GI) and reduce fluctuations in the speckle pattern of the image, the measured data is filtered frame by frame by the number of detected counts per frame, and the GI is smoothed using a moving short-range averaging. We have found that optimizing the filtering procedure leads to a significant reduction in the data acquisition time (down to several seconds) required for obtaining a high-quality GI.

   The molecular geometry in the ground singlet S₀ and lowest triplet T₁ states was optimized, the energies of molecular orbitals were calculated, and the energy of the T₁→S₀ transition was determined for two families of polysubstituted porphyrins and metalloporphyrins with different peripheral substitution architectures, containing either NO₂ groups or NO₂ and NH₂ groups at the Cm-positions of the macrocycle, forming an asymmetric distribution of electronic density in the macrocycle with the density functional theory quantum-chemical calculations. It was found that in poly-NO₂-substituted porphyrins, a change in the number of attached NO₂ groups leads to a similar stabilization of the Gouterman orbitals, which, as a result, does not lead to fundamental changes in the magnitude of the energy gap ΔE(T1–S0). At the same time, a significant decrease in the ΔE(T₁–S0) gap was found in the poly-NO₂-NH₂-substituted porphyrins, caused by substantial stabilization of the LUMO orbital, with conformers with an alternating arrangement of NO₂ and NH₂ groups having a smaller ΔE(T₁→S₀) gap than the conformers with adjacent arrangement of the same groups. It is shown that in all studied porphyrins, the triplet one-electron configurations ³(e_gxa_2u) and ³(e_gya1u) do not mix and the T₁→S₀ transition has a one-electron e_gx→a_1u configuration.

   The absorption and fluorescence spectra of a new benzothiazole dye, monocarbostyril-benzothiazole (Th-C7), containing a carboxyl group as a linker, have been studied. Based on experimental studies and quantum chemical calculations, it has been established that the dye exhibits molecular rotor properties, which is manifested in the strong dependence of the fluorescence quantum yield on the solution viscosity. It is shown that the fluorescence quantum yield of Th-C7 molecules depends on the solvent polarity, which allows this dye to be considered as a solvatochromic molecular rotor.

   This paper presents a generalization of experimental data on microwave discharges in liquids, one of the least studied types of the discharge. The physical characteristics of discharges in liquids are described, and the main differences between microwave discharges in liquids and discharges in gases are shown. It is demonstrated that with increasing incident power, the formation rate increases while the product composition remains unchanged, which is a characteristic feature of discharges in liquids. Examples of applications of microwave discharges for hydrogen production and CO₂ decomposition are given.

   The generation of vapor-gas formation at the surface of metal immersed in liquid under the influence of radiation from GOR-100M laser operating in free generation mode (pulse duration 1.2 ms, flux density ~106 W/cm²) was experimentally investigated. The features of changes in the shape and size of the near-surface formation at different stages of the process, including those after the completion of laser treatment of the material, were studied. Calculations of the temperature and pressure inside the vapor-gas blend were performed according to the proposed methodology. It was established that the significant difference in the shape of the crater surface formed in the result of the impact of a laser pulse with identical parameters on identical samples surrounded by air and water is determined by the fundamentally different nature of the flow of plasma and vapor-gas blend in these cases. It has been shown that when millisecond laser pulses are applied to metal samples located in water, it is possible to obtain nanoparticles and nanostructures.

   CuO/Cu₂O/Y₂O₃/Y₂BaCuO/YBa₂Cu₃O_6.32 composite containing complex oxides was obtained by direct exposing a powder mixture of Y₂O₃, BaO₂, and CuO to pulsed high-voltage discharge plasma. Annealing this composite at 1173 K yielded a Y2BaCuO/CuO/YBa₂Cu₃O_6.91 composite containing the well-known high-temperature superconductor YBa₂Cu₃O_6.91. The presence of a superconducting phase in the resulting composite at T < 87 K was confirmed by data obtained on a vibromagnetometer. The NiCr₂O₄/NiO/Ni composite was obtained by plasma treatment of nichrome wire electrodes. The synthesized sample exhibits a shift in the magnetic hysteresis loop at low temperature, indicating the presence of FM and AFM regions in exchange interaction. The monolithic sample, containing a Cu₂O core coated with a CuO shell, was obtained by plasma treatment of copper wire. The temperature dependence of the sample’s magnetization is characteristic of high-temperature superconductivity. The plasma-chemical methods used are promising for research into the synthesis of new functional materials.

   Chlorine-substituted crystals of methylammonium lead bromide MAPbBr_3–хCl_х, x = 0.01, …, 0.10, were synthesized. The effect of changing the anionic composition on their electrical properties was studied, and the optimal chlorine content was determined to achieve the desired conductivity characteristics. The electronic properties of MAPbBr_3–хCl_х were studied using impedance spectroscopy and optical absorption spectroscopy. High-resolution NMR (¹H) and powder X-ray diffraction were used to confirm the quality of the synthesis.

   In the range of 200–3000 nm, the transmission and reflection of thin (40 μm) polyimide films implanted with 40 keV iron ions at a high fluence of F₁ = 5 ꞏ 10¹⁶ and F₂ = 1.25 ꞏ 10¹⁷ cm^–2 were studied. The integrated transmittance of the films decreases monotonically by more than three times, while the reflectivity changes nonmonotonically: it increases at a low fluence and decreases to the initial value at a high fluence. In addition, a broad reflection band with a maximum at λ ≈ 1000 nm is observed in the implanted films, associated with the formation of iron nanoparticles and/or its compounds. Narrow reflection bands characteristic for the original polyimide in the ultraviolet region are suppressed when reflected by the implanted side and shifted to the short-wavelength region when recorded from the non-implanted surface of the film. The measurement results were interpreted in the framework of a two-layer model: a carbonized surface layer with implanted metal and a polymer film layer unmodified by the implantation. The determined Tauc optical gap of the carbonized layer is negative due to the dominance of the iron-containing phase, and the refractive indices of the modified layer are: n₁ = 2.5 and n₂ = 1.3 at low and high fluences, respectively.

   Thin films of lanthanum oxide doped with erbium, LaMnO₃+0.5%Er₂O₃, deposited in a vacuum of p = 3 Pa on quartz and silicon substrates were studied under multi-pulse high-frequency f ∼ 12—15 kHz laser action on a ceramic target at a laser radiation power density of q = 81 MW/cm². The morphology of the obtained films, transmission and reflection spectra were studied using atomic force microscopy. An analysis of the electrophysical properties of the LaMnO₃+0.5%Er₂O₃ structure was carried out.

   Based on the photoluminescence (PL) and PL excitation spectra of the Cu₂ZnSnSe₄ thin film compound with the kesterite structure the optical width of the direct band gap was determined to be Eg ≈ 1.052 eV at the temperature of 6 K. In the temperature range of 6–300 K the mechanisms of radiative recombination of nonequilibrium charge carriers were established. These mechanisms determine the appearance of wide PL bands in the energy region of 0.7–1.1 eV. For the direct-gap compound Cu₂ZnSnSe₄ with p-type conductivity the effect of redistribution of the intensity between radiative recombination channels in the spectral region of 0.93–0.99 eV was detected, indicating the presence of deep acceptor and donor levels in the band gap. Based on the data on the intensity quenching of broad PL bands in the energy range of 0.7—1.0 eV the thermal activation energy of nonradiative recombination channels involving structural defects was determined and
their nature was discussed.

   The color changes of natural jewelry stones – zircon, andradite, cassiterite – during their heat treatment in various media have been studied. As a result of heating at the same temperature (1100 ℃) using oxidizing conditions (air oxygen), initially almost black zircons obtain a pale-yellow color, and in reducing ones (carbon monoxide) – bright blue. In andradite, in addition to such contrasting color changes, the color reversibility was also noted depending on the heat treatment medium: crystals when repeating the experiment series under the same temperature conditions (830 ℃) in air turned light brown, and in the presence of a reducing agent returned to a saturated green color. Thus, the key factor determining the color changes presented was the heating medium.

   Colloidal quantum dots of the mixed-halide perovskite CsPb_0.8Nd_0.2BrCl₂ containing Nd³⁺ ions were synthesized and characterized. The nanocrystals were obtained by hot injection, followed by purification and transfer to a stable organic dispersion, which ensured the reproducible formation of Nd-containing particles and preserved colloidal stability. A comprehensive set of spectral and morphological studies revealed that the samples exhibit intense blue photoluminescence peaking at 457–458 nm and a narrow emission band. According to excitation-emission mapping, the position of the luminescence band remains virtually unchanged with varying excitation wavelength, indicating the relative homogeneity of the emitting states. The decay kinetics is described predominantly by a monoexponential dependence with a characteristic time of approximately 6.7 ns, and the photoluminescence quantum yield indicates a fairly high proportion of radiative recombination. Morphological analysis, DLS, and EDX mapping confirm the formation of nanoscale particles containing the main elements of the initial composition, including neodymium. It is shown that combined chloride substitution and the introduction of Nd³⁺ ions is an effective approach to obtaining blue-emitting perovskite nanocrystals, which are promising for optoelectronics, photonics, and scintillation applications.

   We performed the hydrothermal synthesis of biocompatible, fluorescent boron nitride nanoparticles (BNNPs). We found that BNNPs accumulated in rat C6 glioma cells and were visualized upon irradiation at 365 nm. The efficiency of BNNP internalization by cells was found to depend on the incubation time and parameters of the medium. As BNNPs at concentrations up to 1 mg/mL had no cytotoxic effect on the cells, they are promising for the use in bioimaging and boron neutron capture therapy.

   A CMOS-based detector for registration atomic emission and fluorescence spectra in environmental monitoring of natural waters has been developed. The detector employs the Hamamatsu S11639-01 CMOS linear sensor together with an STM32F401 microcontroller, providing an inexpensive solution. Dedicated software was developed to control and synchronize the detector and to enable real-time spectral visualization. Experimental tests using laboratory spectral sources demonstrated high sensitivity over the 200–950 nm spectral range and a linear response for exposure times from tens of microseconds up to several seconds. The detector successfully registered spectra of a Hg-Ar lamp as well as fluorescence of fluorescein solution, including low-intensity emission lines. The results confirm the detector’s suitability for portable hybrid sensors capable of simultaneous elemental analysis and fluorescence-based assessment of dissolved organic matter.

   The physical mechanism of reconstruction and amplification of the object wave at diffraction of reference wave by sinusoidal phase-absorption holographic grating formed in cubic optically active photorefractive crystal was studied. In frame of the proposed analytical approach, the vector amplitude of the reconstructed wave is found as the resulting sum of oscillations of diffracted waves of variation amplitude emitted by thin layers of the holographic grating. A polarization condition has been formulated, under which the diffraction efficiency of hologram and the intensity transfer during two-wave mixing reach maximum values. It is shown that the dependences of the output energy characteristics of the phase-absorption hologram on the crystal thickness, calculated on the basis of the analytical approach, are in agreement with the data obtained by solving the coupled waves equations.

   An analysis of experimental studies on two-beam coupling (2BC) revealed that the conclusions about establishing the photorefractive properties of the studied gratings based on the asymmetric temporal fluctuations of the output beams are methodologically inaccurate. In fact, the studies compared the output beams of a Mach–Zehnder interferometer, in which the grating itself serves as the output beam splitter. Comparative experimental studies using a conventional phase surface holographic grating and a photorefractive grating formed in a liquid crystal cell fully confirmed the results of the analysis. It is shown that the inclusion of a chopper, periodically switching on and off one of the incident beams, and a phase modulator for alternating harmonic change of the phase shift between the beams in the standard 2BC set-up ensures the correct establishment of the photorefractive properties of the grating under study.

   We report calculations of accurate high-lying resonance energies of the triplet and the singlet states of the Strontium Rydberg series. Calculations are performed using the Screening Constant by Unit Nuclear Charge (SCUNC) method from n = 12 to 60. This semi-empirical method is widely used in atomic physics to predict energies of excited states without requiring calculation of photoionization cross-sections. Present results are compared with the existing NIST database of Kramidal and Advanced Light Source measurements of Couturier et al. Analysis of the present results is achieved in the framework of the standard quantum-defect theory of the SCUNC procedure. In addition, the present work demonstrates the strength of the SCUNC formalism to assist experimenters in the analysis of measurements.

   In laser-induced breakdown spectroscopy (LIBS), the quantitation accuracy with traditional standard calibration methods is often unsatisfactory, mainly because of the matrix effect. In this work, a novel method named specific-intensity clustering (SIC) was proposed to mitigate the influence of the matrix effect. The specific-intensity, which is defined as the ratio of the spectrum intensity to element concentration, is considered an essential characteristic of a sample. These specific-intensity features facilitate the effective clustering of calibration samples, thereby enabling the establishment of multiple, more robust, calibration curves. By combining the clustered calibration samples with machine-learning algorithms, a classification model was established. Unknown samples can be classified by the classification model and predicted by the proper calibration curve. The feasibility of the proposed SIC method was verified through the detection of CaO, TFe₂O₃, and Li in rock samples. Compared with traditional standard calibration methods, the SIC method significantly reduced the average relative errors of the prediction set (AREPs) for the detected CaO, TFe₂O₃, and Li elements in rocks, with the AREPs decreasing from 25.292, 14.114, and 14.12 % to 6.165, 5.481, and 5.137 %, respectively. This work demonstrates that the SIC method has excellent potential for reducing the influence of the matrix effect in LIBS quantitation.

   BaAl₂B₂O₇ powders activated by RE³⁺ ions (Dy³⁺ and Sm³⁺) were prepared by the solution combustion method. X-ray powder diffraction analysis was used to conduct the phase studies for BaAl₂B₂O₇:Dy³⁺ and BaAl₂B₂O₇:Sm³⁺. A spectrofluorometer operating at room temperature was used to examine the luminescence characteristics of the prepared materials. Under excitation of 350 nm, BaAl₂B₂O₇: Dy³⁺ emitted at 482, 574, and 664 nm, whereas the other phosphor, BaAl₂B₂O₇: Sm³⁺, emitted at 564, 600, 646, and 710 nm following excitation at 402 nm. Thus, this inquiry led to the preparation of two new optical materials that emit visible-spectrum light.

   A series of Eu(III)-Tb(III) co‑doped complexes was synthesized under hydrothermal conditions at 180 °C by reacting europium(III) and terbium(III) perchlorates with 2,4,6‑pyridinetricarboxylic acid (ptc) in systematically varied molar ratios. The molar ratios of Eu(III) to Tb(III) employed during synthesis were as follows: 1.0:0 (1), 0.9:0.1 (2), 0.8:0.2 (3), 0.7:0.3 (4), 0.6:0.4 (5), 0.5:0.5 (6), 0.4:0.6 (7), 0.3:0.7 (8), 0,2:0.8 (9), 0.1:0.9 (10), and 0:1.0 (11). The excitation and emission spectra, luminescence lifetimes, and quantum yields of the complexes were measured. Emission spectroscopy analysis revealed that under ultraviolet excitation, the luminescent color of the complexes gradually shifted from red to orange, yellow, and green as the Eu(III) content decreased and the Tb(III) content increased. Luminescence lifetime measurements showed that the pure Eu(III) complex (1) exhibited the shortest lifetime. In the co-doped complexes, the lifetime of the Eu(III) ⁵D0→⁷F₂ transition gradually increased as the Eu(III) content decreased. Conversely, the pure Tb(III) complex (11) displayed the longest lifetime, and the lifetime of the Tb(III) ⁵D4→⁷F₅ transition decreased rapidly as the Tb(III) content was reduced. Absolute quantum yield (QY) measurements indicated that the pure Eu(III) complex (1) had the lowest QY, whereas the pure Tb(III) complex (11) showed the highest. Among the co-doped complexes (2–10), the QY gradually increased with decreasing Eu(III) content, and correspondingly decreased with increasing Eu(III) content. These results suggest that in this series of complexes, Tb(III) can sensitize the luminescence of Eu(III), whereas Eu(III) exerts a quenching effect on the luminescence of Tb(III).

   A systematic investigation was carried out on samarium (Sm³⁺)-doped NaBaPO₄ orange–yellow-emitting phosphors synthesized via a solid-state process in an air atmosphere, focusing on determining how the crystallization behavior and luminescence mechanisms are affected by the calcination time and dopant concentration. The phase formation and optical properties were characterized using thermogravimetry, X-ray powder diffraction, and photoluminescence spectroscopy. The results demonstrate that the sample calcined at 750 ℃ forms the main phase of hexagonal NaBaPO₄ (space group P3̅m1), which contains two distinct crystallographic sites for Ba2+ ions. Excitation at 400 nm reveals strong near-UV absorption, indicating suitability for matching LED devices. The emission spectra exhibit transitions at 564 nm (⁴G_5/2→⁶H_5/2, magnetic dipole), 600 nm (⁴G_5/2→⁶H_7/2, mixed character), and 644 nm (⁴G_5/2→⁶H_9/2, electric dipole). The hypersensitivity of the ⁴G_5/2→⁶H_9/2 transition to the local crystal field enables precise emission tuning via symmetry engineering. Variations in the red-to-green intensity ratio of the emission peaks with Sm³⁺ content allow modulation of the chromaticity coordinates and color purity. Among the investigated samples, the maximum emission intensity is achieved by NaBa_0.97PO₄:0.03Sm³⁺, for which the quenching mechanism is identified as multipole–multipole interactions. Additionally, the highest color purity (96.3 %) is also achieved by this phosphor, exhibiting a highly saturated color.

   We have successfully synthesized the antibacterial nanomaterial silver zirconium phosphate (AgZrP) via a precipitation method combined with ion exchange. The X-ray diffraction pattern of the AgZrP hot lattice at 900 °C for 2 h revealed a single-phase structure belonging to the cubic space group (hexagonal). The morphological properties and chemical composition were comprehensively analyzed using transmission electron microscopy and energy-dispersive spectroscopy. Simultaneously, surface bond vibration modes were analyzed via infrared spectroscopy. The study facilitated the determination of key technological parameters for the synthesis of AgZrP antibacterial nanopowder, including temperature, precursor concentration, and calcination time. The resulting powder exhibited a size of about 50 nm and demonstrated 5–6 times higher antibacterial efficacy against Escherichia coli compared with silver nanomaterials (with an antibacterial circle diameter reaching 32 mm at a powder concentration of 100 ppm). The AgZrP nanopowder product demonstrates significant potential for use as an antibacterial material in civilian applications.

   The widespread use of plastic products has resulted in the pervasive presence of microplastics in both marine and freshwater environments, posing significant risks to aquatic ecosystems. Accordingly, the development of accurate and rapid detection methods for microplastics is an urgent priority. Conventional techniques are often time-consuming and require complex sample preparation. To overcome these limitations, we propose a micro-Raman spectroscopy-based method for the detection and identification of microplastics in flowing water, which eliminates complex sample pretreatment and substantially reduces analysis time. The minimum detectable particle size was 26 μm. Unlike conventional approaches, this method simultaneously acquires particle size and Raman spectral information, enabling rapid detection without complex sample preparation. The approach shows potential for real-time monitoring of microplastics in flowing tap water and marine environments.

   To achieve nondestructive and accurate detection of acetamiprid (ACE) in black tea, a method based on ultraviolet (UV) absorption spectroscopy and chemometrics is proposed. First, the absorption spectra of 60 black tea samples containing varying ACE concentrations are acquired using a UV-visible spectrophotometer. Afterward, the effective variables are extracted by bootstrapping soft shrinkage (BOSS), the successive projections algorithm (SPA), and the competitive adaptive reweighted sampling (CARS) algorithm. Finally, the prediction models are developed using partial least-squares regression (PLSR) and gray wolf optimizer least-squares support vector regression (GWO-LSSVR). The results demonstrate that the CARS-GWO-LSSVR model performs best, with a determination coefficient (Rp2) and root mean square error for the prediction set (RMSEP) of 0.9991 and 0.0994 mg/L respectively. Furthermore, to assess the feasibility of the proposed method under interference from other pesticides, experiments are conducted using imidacloprid as an interferent. The results demonstrate that the method exhibits high-precision detection of ACE in black tea even in the presence of such interference. Thus, UV absorption spectroscopy combined with chemometrics can achieve nondestructive and accurate detection of ACE in black tea.

   This study employed advanced in situ visualization techniques to investigate the mass-transfer enhancement mechanisms of heavy oil components in fluid catalytic cracking (FCC) catalysts. Three FCC catalysts with different matrix compositions were selected: CAT-1 (kaolin), CAT-2 (kaolin/APM-7), and CAT-3 (kaolin/APM-9). Their pore structures were systematically characterized using SEM and N2 adsorption-desorption. In situ visualization of the diffusion of Rhodamine B-tagged heavy oil components (probe size: 2–5 nm) within the catalyst pores was achieved by laser confocal fluorescence microscopy at a resolution of 200 nm. The results demonstrated that CAT-3, modified with APM-9, exhibited an optimal mesoporous structure (with 35 % of pores in the 3–5 nm range) and achieved an effective diffusion coefficient of 1.84×10–13 m2/s, which is 7.3 times higher than that of the conventional kaolin-based CAT-1. Analysis using the Yoon–Nelson model further confirmed a 68 % reduction in the adsorption rate constant for CAT-3, revealing the synergistic enhancement effect between hierarchical pore channels and acid sites. This study established a quantitative structure-performance relationship between pore architecture and mass transfer in FCC catalysts, facilitated by the development of an in situ fluorescence visualization technique for probing diffusion within porous materials. This study not only provides a quantitative “pore structure–mass transfer” relationship model for the rational design of FCC catalysts, but also offers a novel characterization method with high spatiotemporal resolution for investigating the mass-transfer mechanism of porous materials.

   The use of Laguerre–Gaussian (LG) laser beams in particle acceleration provides a promising pathway for advancing laser-driven acceleration schemes. We investigate electron acceleration resulting from the interaction of LG beams with charged particles. A comprehensive theoretical framework is formulated to elucidate the underlying acceleration mechanisms, complemented by detailed numerical simulations. The electron dynamics in the structured electromagnetic fields of the LG beam are systematically analyzed, revealing distinctive acceleration behavior along the direction of beam propagation. Our results demonstrate that the orbital angular momentum and spatial field structure of LG beams enable controlled and efficient electron acceleration. These findings highlight the potential of LG beams as a viable tool for tailored electron acceleration and contribute to the broader development of advanced laser-plasma and laser-based acceleration techniques.

   A novel analytical method using reflectance NIRS combined with PLS multivariate calibration to determine fidaxomicin in tablet formulations has been developed and validated. NIR diffuse reflectance spectroscopy in reflectance mode is a versatile technique used for analyzing the optical properties of materials by combining reflection and transmission measurements. Partial least squares regression was used to establish the relationship between the IR peaks and fidaxomicin concentrations in a known standard. Metrics evaluated included correlation coefficient (R²), root mean squared error of cross-validation (RMSECV), bias, and relative percentage difference (RPD). Figures of merit, including linearity, precision, accuracy, ruggedness, selectivity, and analytical sensitivity, were assessed in accordance with ICH guidelines. Model performance was as follows: R² = 99.9, indicating excellent predictive capability; RMSECV = 4.19, reflecting low prediction error; bias 0.639; RPD 31.3. The method was validated as linear, precise, accurate, and rugged. The proposed NIR-PLS method is a viable alternative to HPLC for fidaxomicin quantification, offering advantages in speed, simplicity, cost, and environmental sustainability. By adhering to ICH guidelines, the method demonstrated reliability and applicability for routine pharmaceutical quality control.

   Mycophenolate mofetil is an immunosuppressive agent approved by the Food and Drug Administration. The present report describes the validation of two simple, economical, and highly sensitive spectrofluorimetric methods based on the native fluorescence of the drug in ethanol and in alkaline medium. Fluorescence characteristics of the drug were found to significantly differ in absolute ethanol (λ_ex = 268 nm and λ_em = 426 nm) and in NaOH (λ_ex = 359 nm and λ_em = 434 nm). Both the methods were validated as per the ICH guidelines. Stress degradation studies were conducted on the drug as per the ICH guidelines and excellent recovery from the stressed samples suggested the stability-indicating nature of the methods. The two methods were found to be extremely sensitive, precise, and accurate, demonstrating excellent linearity in the concentration ranges 0.5–15.0 μg/mL (absolute ethanol) and 0.1–8.0 μg/mL (NaOH). The limit of detection and limit of quantitation values were found to be 0.52 and 1.57 µg/mL (absolute ethanol), and 0.02 and 0.07 µg/mL (NaOH), respectively. The proposed methods afforded excellent recovery of mycophenolate mofetil from its marketed tablet formulation, thus suggesting that these methods could be employed for routine analysis of the drug in bulk as well as in formulation.

    The goal of the present investigation was to develop a simple, accurate, precise, robust, and cost-effective UV-spectroscopic technique for the quantitative estimation of xanthohumol in bulk and hydrogel, in accordance with the International Conference on Harmonisation guidelines.

   The λ_max of xanthohumol was found to be 363 nm with y = 0.06363x + 0.0115 as the regression equation, a 0.9968 regression coefficient, and showed linearity in the range 2–14 μg/mL. Relative standard deviation (% RSD) values for intraday analysis were 1.105, 0.936, and 0.32, whereas for inter-day analysis, these values were 1.312, 0.433, and 0.979 (< 2 % RSD). RSD for absorbance values analyzed using different spectrophotometers was 0.886 and 1.242 %, and by different analysts it was 0.647 and 1.044 % (< 2% RSD), which validated the ruggedness parameter. RSDs for absorbance values analyzed at 361, 363, and 365 nm were 0.761, 1.045, and 0.885 %, respectively (RSD < 2 %), indicating robustness. The mean recovery of xanthohumol in the presence of carbopol-934 was in the range 98–102 %, which validated its specificity. The limit of detection (LOD), limit of quantitation (LOQ), and Sandell’s index for xanthohumol were 0.639, 1.939 µg/mL, and 0.017278 µg/cm² per 0.001 absorbance unit respectively, indicating higher sensitivity of the analytical method for xanthohumol detection. Xanthohumol-loaded carbopol-934 hydrogel was formulated by dispersing xanthohumol in carbopol-934 and neutralizing it with triethanolamine. The solubility of the bulk form of xanthohumol in phosphate buffer at pH 6.8 was 1.153 µg/mL, which was enhanced to 4.12 µg/mL by the production of xanthohumol-loaded Carbopol hydrogel.

   This study describes the development and validation of two UV-visible spectrophotometric methods for the simultaneous quantification of sitagliptin phosphate monohydrate and gliclazide in fixed-dose pharmaceutical formulations. The combination, which was recently approved by the Central Drugs Standard Control Organization (CDSCO) in 2023, is used in the management of type 2 diabetes owing to its complementary pharmacological mechanisms and favorable safety profile. Spectrophotometry was selected as a simple, cost-effective yet reliable alternative to chromatographic techniques for routine quality-control analysis. Two methods – simultaneous equations and first derivatives – were developed using HPLC-grade methanol as a solvent and analyzed with a Shimadzu UV-1800 double-beam spectrophotometer. Method validation was conducted in accordance with International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) Q2(R2) guidelines. The methods demonstrated excellent linearity across the concentration ranges of 8–56 μg/mL for sitagliptin and 4.8–33.4 μg/mL for gliclazide, with correlation coefficients exceeding 0.999. Accuracy studies yielded recovery within acceptable limits, and precision was confirmed by low relative standard deviations. The first-order derivative method utilized zero-crossing wave-lengths of 213.2 nm (sitagliptin) and 243.6 nm (gliclazide), whereas the simultaneous-equation method used λ_max values of 268.0 and 228.4 nm, respectively. Both methods showed high sensitivity (limit of detection, limit of quantitation), reproducibility, and robustness. Statistical comparison using one-way ANOVA revealed no significant difference (p > 0.05) compared with previously reported methods, confirming analytical equivalence. These validated methods are suitable for routine quality assessment and regulatory compliance of combined formulations, with future applicability in biological matrices.