NH-tautomeric equilibria of the free base corroles in the ground S₀ and lowest excited singlet S₁ states in solutions were studied using absorption and fluorescence spectroscopy. It was found that in the ground singlet S₀ state the NH-tautomeric equilibrium shifts toward stabilizing the long-wavelength T1 tautomer with  an increase in the solvent ability to form intermolecular hydrogen bonds. The magnitude of the shift is proportional to the weighted sum of the solvent Kamlet-Taft constants α and β. It was established that the general solvent interactions in the lowest excited singlet S₁ state stabilize the short-wavelength T2 tautomer with increase in the solvent polarity (Lippert function Δf), while the specific interactions (intermolecular hydrogen bonds) stabilize the long-wavelength T1 tautomer. The obtained dependences are analyzed in the framework of the model of multicenter intermolecular interactions in macroheterocyclic core.

The Raman spectra of hematite in the paint layer of a model fresco sample were compared before and after heating to 740°C. A significant obstacle to the analysis of the Raman spectra of hematite is the significant difference in the relative line intensities in the spectra measured at different points on the sample. It is shown that such differences are due to the orientation factor – a change in the Raman line intensities with changes in the relative orientation of hematite microcrystals and the wave vector of the exciting radiation. To minimize the orientation effect, it is proposed to average a series of spectra measured at different points on the sample. Comparison of the averaged spectra before and after heating allows us to identify a number of changes.  An increase in the intensity of the calcite lines may be associated with thinning of the paint layer, and the appearance of amorphous carbon lines is possibly due to the charring of organic components in the plaster. Heating also leads to an increase in the intensity of the line at 660 cm^–1, indicating an increase in the defectiveness of hematite microcrystals. It is hypothesized that the decrease in the intensity of the line at 221 cm^–1 and the increase in the intensities of the lines at 406 and 605 cm^–1 may be due to the orienting effect of heating on the pigment microparticles. The obtained data can be used to interpret the condition of historical frescoes in churches exposed to fire.

Raman reflection spectra have been studied on single crystals of (In₂S₃)_хꞏ(AgIn₅S₈)_1–х solid solutions grown by vertical directional crystallization in the frequency range of 100–2000 cm^–1. It has been established that for this type of compounds, four active vibrational modes appear in the frequency range of 100–400 cm^–1. All vibrational modes were identified, and the crystal lattice type was determined. The full width at half maximum values were calculated, confirming the crystalline structure of the samples. Concentration dependences of the A₁g, E_g, 2F_2g modes were plotted. It was found that with a change in the solid solution composition, the vibrational modes exhibit a monotonic behavior – they smoothly shift with varying x from frequencies characteristic of AgIn₅S₈ to those characteristics of the In₂S₃ compound.

Stimulated Raman scattering (SRS) was studied in a grown by chemical vapor deposition (CVD) diamond mono-crystal placed in the cavity of a microchip laser. The microchip laser was built on a composite crystal: an Nd³⁺:YAG active element and a Cr⁴⁺:YAG passive Q-switch. Pumping was performed by a diode laser  (λ = 808 nm) with a power of 2.2–4.5 W. Varying the pump power led to a change in the repetition rate of pulses generated at a wavelength of λ = 1064 nm between 7 and 30 kHz. The laser pulse energy, depending on the experimental conditions, varied in the range of 5.1–10 μJ, while their duration was in the range  of 2—3 ns. The pulses of the first Stokes component (λ = 1240 nm) had an energy of 1.75–3.75 μJ, and their pulse-width, compared to laser pulses, was compressed to 0.6 ns.

With line-by-line method the simulation of transmission of IR-radiation by water vapor tritium isotopologues was conducted with concentration variations in multi-component gaseous medium. The parameters of lines broadening of H₂O tritium isotopologues were calculated. The sensitivity of trace IR-spectroscopy method for detecting HT¹⁶O, T₂¹⁶O, and DT¹⁶O in radioactive water evaporation was estimated.

The pulsed cathodoluminescence (PCL) spectra of mixtures of gallic acid with humic acids of various origins (10, 30, 50, 70, and 90 wt.%) were studied. PCL spectra were recorded in the range from 350 to 850 nm after irradiation with an electron beam duration of 2 ns and with an average energy of 170 keV. The number of irradiation pulses at a repetition rate of 1 Hz varied from 20 to 4000. In many mixtures, PCL was absent or had very low intensity. In those mixtures where luminescence was recorded, the spectrum differed from the spectrum of gallic acid in the absence of humic acids and corresponded to the luminescence of its base form. Gallic acid was shown to be incorporated into the humic acid structure, forming hydrogen-bonded complexes.

The phenomenon of sonotriboluminescence in suspensions of terbium(III) and europium(III) sulfate microcrystals containing benzo[a]pyrene in n-heptane (an extractant used for the extraction and concentration of benzo[a]pyrene during analysis) was investigated. It was shown that under ultrasonic cavitation treatment of the suspension, the luminescence spectra exhibit characteristic emission bands of monomeric benzo[a]pyrene molecules. These fluorescence bands are identical to the photoluminescence spectra of a benzo[a]pyrene solution. The concentration dependence of the sonotriboluminescence intensity of benzo[a]pyrene molecules in the luminescence spectra of the suspensions was obtained, with a detection limit of ~10^–7 mol/L. To enhance the luminescence yield, a mechanism of intermolecular nonradiative energy transfer involving benzene as a donor was implemented. The addition of benzene leads to a sensitized increase in the luminescence of benzo[a]pyrene molecules, thereby improving the detection efficiency at low concentrations. The obtained results demonstrate the fundamental feasibility of using the sonotriboluminescence effect in dispersed systems for the luminescent detection of polycyclic aromatic hydrocarbons (using benzo[a]pyrene as an example) in liquid hydrocarbons.

Using a two-component system based on indotricarbocyanine dye in low-polarity o-dichlorobenzene as an example, this article examines an approach to analyzing the spectral-kinetic properties of multicomponent systems aimed at determining a physically consistent model for approximating fluorescence decay kinetics. Data analysis was performed using a developed software module that allows one to determine the fluorescence decay duration of one or more centers and set conditions for the search region of the calculation model parameters. The ability to obtain a posteriori distribution of the approximation model parameters is also implemented to determine the range of their possible values. It has been shown that when deconvoluting the fluorescence decay curves of multicomponent systems, achieving the minimum value of χ² (a value less than 1.2) is not a criterion for reliably determining the weighting coefficients and durations of fluorescence decay of the components; it is necessary to use not only mathematically determined calculation conditions, but also to compare the calculated parameters with other photophysical characteristics of each of the components.

The mechanisms of interaction of styrylcyanine dyes Sbt ((E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]thiazol-3-ium iodide), Sbo ((E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]oxazol-3-ium iodide), Sil ((E)-2-(4-(dimethylamino)styryl)-1,3,3-trimethyl-3H-indolium perchlorate) and their homodimers Dbt-10, Dbo-10, Dil-10 with human serum albumin were studied by time-resolved fluorescence spectroscopy. A significant increase in the fluorescence quantum yield of the homodimer dyes upon their binding to human serum albumin was found. The binding constants (K_b) of these dyes to albumin were determined and were found to depend on the molecular structure of the probes. The preferred binding sites of the studied dyes within the albumin globule were identified. Molecular modeling results showed that hydrophobic interactions and hydrogen bonds with amino acid residues of the protein play a key role in stabilizing the complexes.

The results of complex study of thin ZrО₂ films deposited in vacuum (p = 2.2 Pa) on quartz and silicon substrates under multipulse high-frequency (f  10—12 kHz) laser action on the ceramic target at a laser power density q = 79 MW/cm² were presented. The morphology of the obtained films was studied using atomic force microscopy, the features of the transmission spectra were presented. The analysis of the electrical properties of ZrО₂/Si structure was carried out.

It was shown that the phenomenon of multiple gamma-quantum production resulting from the radiative capture of neutrons by gadolinium nuclei can be used to increase the neutron selectivity of scintillation detectors. A detector design is proposed in which 16 optically isolated gadolinium containing scintillators are connected to the silicon photomultipliers matrix, and event selection is performed in coincidence mode based on the number of channels from which a signal is received. It is shown that selecting events for which three or more channels were triggered, suppresses the background gamma-quantum counting rate by 114 times and the neutron counting rate by 21 times, thereby increasing the neutron selectivity by 5.6 times.

Based on expressions for radiation forces acting on a transparent spherical nanoparticle in the field of a focused Gaussian beam, an equation of motion of a nanoparticle along the optical axis in a liquid medium is constructed taking into account the viscous Stokes drag and thermal fluctuations. The Langevin equation of the first order with the initial condition is formulated. The analysis of stationary points and linearization of the resultant force near the position of stable equilibrium are carried out. Analytical expressions for the stationary distribution of the particle’s coordinate are obtained and the contribution of Brownian motion as a function of the particle’s radius is estimated. The influence of the focal length and the input beam radius on the magnitude of the maximum restoring force and the root-mean-square Brownian force is analyzed. It is shown that for particles with a radius of less than a few tens of nanometers, thermal fluctuations destroy optical capture.

The paper presents the results of calculations of the spectral dependences of the extinction efficiency factors Q_ext, near-field enhancement Q_NF, and absorption Q_abs for spherical silver nanoparticles (radii of 5, 15.5, and 35 nm) performed using the extended Mie theory. The particles were considered in transparent  (κ = 0) and absorbing (κ = 0.05 and 0.2) matrixes with a high refractive index of n_m = 2.0. It was found that even a small absorption in the matrix leads to a significant decrease in the maxima of Q_ext and, especially, Q_NF. In this case, the position of Q_ext peaks remains virtually unchanged, while a slight long-wavelength shift is observed for Q_NF. It is shown that for particles with the radius of 35 nm at κ0.05, the maxima of Q_NF and Q_abs factors in the quadrupole mode region significantly prevail over the dipole ones, which is not typical for the extinction factor Q_ext. Significant differences in the spectra and near-field distributions of nanoparticles in real absorbing media (CuPc and NiPc) were revealed. Despite the chemical similarity of the molecules, the dispersion of their refractive indices leads to radically different optical responses of the hybrid system.

Vortex Bessel beams (VBBs) generated by an optical system consisting of two axicons with a small difference in cone angles and a spiral phase plate are studied using analytical and numerical methods. A method for producing vortex annular beams is proposed based on apexing the VBBs at the first minimum of the intensity distribution. It is shown that, compared to nonvortex annular beams of the same power generated by a two-axicon system, these beams are characterized by a single ring maximum in the transversal intensity distribution and suppressed diffraction divergence of the axial minimum. It is established that apexing the VBBs at the second minimum enables the formation of light beams whose diffraction broadening of the axial minimum is negligible at distances up to hundreds of meters. The suppressed diffraction broadening of the axial minimum dimensions at significant distances expands the possibilities of practical application of the proposed vortex ring beams to areas where stable singularities of the wave field are needed, in particular, for quantum information encoding, data transmission in free space, and for three-dimensional nanoscopy.

This paper examines the physical and technical aspects of implementing a method for measuring the absolute spectral response and photon detection efficiency (PDE) of highly sensitive silicon photomultipliers (SiPMs) using laser radiation sources. The proposed method takes into account the contribution of the charge of time-correlated optical interference and enables high-precision measurement of SiPM parameters. The results of testing by this method are presented using packaged SiPMs, one of which of the S13360-1350CS type from “Hamamatsu” (Japan), has been used as a standard of comparison, and another one is KОF 1350  (JSC “INTEGRAL”, Belarus). These SiPMs have single pixel dimensions of 5050 μm and a light-sensitive area of approximately 1.7 mm². For the KOF-1350 SiPM, it was found that with an increase in overvoltage from 3 to 5 V, the coefficient K quickly increases from 0.19 to 0.43.

A methodological approach has been developed using diffuse reflectance spectroscopy in the UV-Vis-NIR range in combination with machine learning methods to construct classification models for grading soybean seeds into groups based on the type of defect and by food quality category. Classification models for soybean seeds by defect groups and quality categories were developed. Over a wide spectral range (350–2500 nm),  a set of five informative spectral bands was identified, attributed to functional groups of soybean seed components and making the greatest contribution to seed grading into quality categories. Classification functions were obtained that can be used to assign new samples to specific categories. The soybean seed classification model has sufficient accuracy (90%). Reducing the number of spectrum wavelengths allows for a significant reduction in the time required for data processing and decision making.

Accurate determination of trace uranium in aqueous systems is essential for reliable spectroscopic analysis, yet laser-induced fluorescence (LIF) measurements of uranyl ions are often affected by matrix interference. In this study, the effects of common coexisting ions (Fe³⁺, Al³⁺, Mg²⁺, SO₄²⁻, and NO³⁻) on uranyl fluorescence signals were systematically investigated. Using a controlled variable approach, mixed solutions that contained fixed uranium concentrations (1 and 20 ng/mL) and varying concentrations of interfering ions  (1–100 μg/mL) were analyzed with a WGJ-III microuranium analyzer. The results demonstrate that different ions exhibit distinct interference behaviors that lead to fluorescence quenching or signal modulation depending on the ion type and concentration. The observed effects are discussed in terms of possible spectroscopic and chemical interaction mechanisms that influence uranyl fluorescence. This work provides a quantitative assessment of matrix interference in LIF-based uranium determination and offers useful insights for improving analytical accuracy in spectroscopic uranium analysis.

Accurate identification of kidney stone compositions is critical for optimizing clinical diagnoses and formulating individualized treatment plans. This study developed a rapid, noninvasive method for classifying kidney stone types via laser-induced fluorescence (LIF) spectroscopy combined with machine learning, establishing a 405 nm laser-based LIF system to collect spectral data for four common stone types: calcium oxalate monohydrate, anhydrous uric acid, magnesium ammonium phosphate hexahydrate, and carbonate apatite. Spectral data were preprocessed using standard normal variate transformation and normalization to reduce noise and morphological variability. Following feature selection and scaling, four classification models  (e.g., K-nearest neighbors, support vector classifier, random forest, and eXtreme gradient boosting) were constructed, with hyperparameters optimized via a Bayesian algorithm. All models performed well on an independent test set, with the support vector classifier achieving the highest average accuracy of 92%. This proposed technique enables reliable and efficient identification of the intraoperative stone components and holds significant potential for enhancing clinical diagnostics, guiding personalized treatment, and supporting recurrence prevention.

A series of Sr₃WO₆ phosphors activated with Ho³⁺ and co-doped with alkali ions were prepared for lighting applications. X-ray diffraction (XRD) patterns confirm the formation of a triclinic crystal structure of the materials. Upon monitoring the emission at 545 nm, all samples exhibit a prominent excitation band centered at 451 nm. Excitation at this wavelength produces an intense green emission at 545 nm, which is attributed to the allowed ⁵S₂/⁵F₄–⁵I₈ transition of Ho³⁺ ions. With increasing Ho³⁺ concentration, the photoluminescence (PL) intensity increases up to 3 mol%, after which concentration quenching is observed. To improve luminescence performance, Sr₃WO₆:Ho³⁺ was co-doped with alkali metal ions. Incorporation of Li⁺ significantly enhances the emission intensity, whereas Na⁺ and K⁺ co-doping produces only marginal improvement. Later, the Sr₃WO₆:Ho^3+, Li⁺ is further optimized by varying the Li⁺ concentration up to 7 mol%. As a result, 5 mol% Li⁺ co-doping gives the highest PL intensity. To check the photometric analysis, the CIE colour coordinates of all three co-doped samples have been calculated. Overall results suggest that the Sr₃WO₆:Ho^3+, Li⁺ phosphor holds significant potential to be used in green lighting applications. 

For rapid quantitative detection of chlorpyrifos, an enhanced technique integrating colorimetric spectroscopy and chemometrics was created. Based on the molecular structure of chlorpyrifos, palladium chloride and resorcinol were selected as colorimetric reagents, with hydrochloric acid and acetic acid used as solvents for palladium chloride, respectively. Three distinct colorimetric systems were constructed to react with chlorpyrifos at varying concentrations. By comparing the absorbance spectra after the colorimetric reactions, the palladium chloride-acetic acid solution was idjentified as the most effective colorimetric reagent, capable of distinguishing absorbance signals for chlorpyrifos concentrations as low as 0.01 mg/kg. For 50 chlorpyrifos samples (0.01–88 mg/kg), the optimal model was selected by evaluating four key parameters: the determination coefficients of the calibration set (R_c²) and the prediction set (R_p²), together with the root mean square errors of calibration (RMSEC) and prediction (RMSEP). The partial least squares (PLS) regression model achieved R_c² = 0.9975, RMSEC = 1.3383 mg/kg, R_p² = 0.9948, and RMSEP = 1.8614 mg/kg. This sensitivity meets the detection limits specified for certain food products in the Chinese National Standard GB 2763-2021. The method is operationally safe, requires only 2 minutes for the colorimetric reaction, and provides a practical basis for developing detection instruments for other sulfur-containing organophosphorus pesticides.

Zinc oxide nanoparticles were synthesized within 15 min using an argon plasma jet and Pseudomonas aeruginosa bacteria extract. X-ray diffraction confirmed a high-purity hexagonal phase with 26.3 nm as the average crystallite size. Field emission scanning electron microscopy verified the surface topography, revealing spherical particles with sizes up to 46 nm, which was consistent with atomic force microscopy, indicating an average grain size of 46.81 nm. The material’s composition and purity were further verified by energydispersive X-ray spectroscopy, showing no impurities. Fourier transform infrared spectroscopy identified  Zn–O absorption peaks at 676, 608, and 477 cm⁻¹, and UV-Vis spectroscopy revealed an optical bandgap of 3.4 eV. Using both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, the disc diffusion technique was used to assess antibacterial efficiency, demonstrating the inhibition of these bacteria. Overall, this cost-effective method is effective in efficiently synthesizing zinc oxide nanoparticles, making it suitable for developing novel bactericides.

GO-SiO₂, GO-TiO₂, and GO-ZnO nanocomposites were synthesized via sol-gel and ultrasonic dispersion processes and then coated on glass substrates using spray pyrolysis and plasma jet-assisted spray pyrolysis. The primary objective was to investigate the influence of atmospheric-pressure plasma activation on the morphological evolution and electronic band structure of these nanocomposites. Results of XRD and FTIR analyses showed that plasma treatment induced a partial reduction of Graphene oxide (GO) into rGO (indicated by a peak at 27°) and increased the density of oxygen-containing functional groups, leading to significantly better interfacial adhesion and stability. The absence of distinct metallic oxide peaks in the XRD patterns suggests their existence in an amorphous or ultra-fine nanocrystalline state. Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy confirmed that the SiO₂, TiO₂, and ZnO particles were evenly distributed, with plasma preventing local aggregation. Investigation of the optical properties via UVVis and photoluminescence (PL) spectroscopy indicated that the plasma treatment profoundly affected the electronic structure, reducing the energy gap (E_g) from 2.18 and 2.87 eV to 1.15 and 1.50 eV for GO-SiO₂ and GO-TiO₂, respectively. The plasma-treated samples exhibited higher PL intensity, signifying increased radiative recombination; this enhancement positions these materials as excellent candidates for luminescent downshifting layers. In this capacity, the films act as spectral converters that optimize the spectral response of photovoltaic systems, making them highly suitable for advanced optoelectronic and sensor applications.

Temozolomide is a DNA alkylating agent used to treat specific types of brain cancer. This report describes the validation of simple, rapid, sensitive, and cost-effective zero-order, first-order, and second-order derivative spectrophotometric methods for the estimation of temozolomide in bulk and in its marketed formulation. Preliminary spectrophotometric analysis of the drug was carried out in sodium hydroxide (0.1 N) and hydrochloric acid (0.1 N), and a total of 25 parametric variations were explored. Three method variants employing absorbance (zero-order), peak-to-peak (first-order), and peak-to-zero (second-order) techniques were validated for linearity, accuracy, precision, and robustness. The developed method was validated with respect to parameters including linearity, accuracy, precision, robustness, and solution stability. Excellent linearity was observed in the concentration range of 5.0–40.0 μg/mL, with correlation coefficients of 0.99 or higher for the selected method variants. The assay detection limits ranged from 0.53–1.09 μg/mL, and quantitation limits ranged from 1.61–3.33 μg/mL for the proposed method variants. The proposed methods were used to quantify the drug in its marketed tablet formulation, yielding good recoveries ranging from 97.50–99.05%.

A cost-effective, environmentally friendly UV-visible spectrophotometric method for the quantitative determination of catechin hydrate in pure form using hydroalcoholic solution of 0.01% (v/v) ethanol has been developed and validated. The aim of the study was to develop a sustainable analytical instrument for use in quality control purposes in resource-poor environments. The method was validated as per ICH guidelines, and different validation parameters such as linearity, accuracy, precision, sensitivity, and robustness were investigated. It is found that the method possesses good linearity over the range of 2–20 µg/mL with R² = 0.9976 and λ_max = 278 nm. Good accuracy of the method was obtained by means of recovery experiments, as percentage recovery values varied between 99.39 and 99.48%. Precision of the method was ensured through an acceptable percentage relative standard deviation (%RSD). The LOD and LOQ values for catechin hydrate were determined to be 0.523 and 1.585 µg/mL, respectively. The solubility of catechin hydrate in the solvent system was 114.631 µg/mL, as tested. Environmentally, the overall sustainability of this method, as measured by the Analytical Greenness (AGREE) tool, scored 0.84, and it was highly aligned with the principles of green analytical chemistry. In general, the method proposed is suitable for routine pharmaceutical and nutraceutical quality control analysis.

A simple, sensitive, and cost-effective spectrophotometric method was developed for the quantitative determination of desidustat in pharmaceutical formulations, using molecular iodine as a complexing agent. Desidustat, a hypoxia-inducible factor prolyl hydroxylase inhibitor used to treat anaemia, was analyzed based on the interaction between iodine and a secondary amine group, where coordination occurs through the lone pair of electrons, resulting in the formation of a stable hyperiodine complex. The resulting coloured ion-pair complex exhibited a distinct hyperchromic shift, with maximum absorbance at 235 nm. The proposed method was validated in accordance with the International Council for Harmonisation guidelines. The method demonstrated excellent linearity over the concentration range of 0.25–1.0 μg/L, with a correlation coefficient (r²) of 0.9995. The limits of detection and quantitation were 0.00459 and 0.01378 μg/L, respectively, indicating high sensitivity. Method precision was confirmed through intra- and inter-day studies, yielding mean recovery values of 100.38 and 100.22%, respectively. Accuracy studies showed satisfactory results, with mean percentage recoveries ranging from 99.41 to 99.87%. The validated method was reliable, precise, and suitable for the routine analysis of desidustat in pharmaceutical dosage forms, offering a straightforward alternative to more complex analytical techniques.

This study aimed to develop a novel, rapid, and precise UV spectrophotometric method for quantifying Vonoprazan in both pure and tablet dosage forms. On the basis of an extensive evaluation of solubility, stability, toxicity, and carcinogenicity, and in line with eco-friendly approaches, a mixed phosphate buffer solution (pH 6.8) was employed as the solvent. Spectrophotometric analysis was performed within the 200–400 nm wavelength range. A distinct absorption maximum was identified at 237 nm, and strong linear relationship (r = 0.998) was observed, indicating compliance with Beer’s law within the 10–30 μg/mL concentration range. Furthermore, the recovery of Vonoprazan ranged from 98.01 to 101.25% (w/w), confirming the method’s accuracy. Precision of the method was confirmed by the percentage relative standard deviation, which remained within acceptable limits as per guidelines. Compliance with the stringent requirements of ICH Q2 (R1) was ensured throughout the entire evaluation process. Assessment of the method’s greenness was carried out using the Analytical Eco-Scale, AGREE metrics, and GAPI. Findings from the greenness evaluation and analytical merits confirmed the method’s reliability and supported its suitability as an improved alternative for Vonoprazan analysis.

The present study describes the development and validation of QbD-assisted UV-Visible spectrophotometric methods for the quantitative determination of rizatriptan benzoate. The spectrophotometric determination was performed between 200–400 nm and the absorbance was compared to the wavelength. The developed method was validated according to the ICH guidelines for specificity, linearity, precision, accuracy, ruggedness, robustness, repeatability, forced degradation studies, and greenness assessment. The precision of the developed method was evaluated by calculating the percentage relative standard deviation (%RSD). The obtained %RSD values were within the acceptable limits specified by regulatory guidelines, confirming the method’s satisfactory precision and reliability for routine analytical applications. The accuracy of the developed method was evaluated and expressed as the percentage mean recovery which demonstrates the closeness of agreement between the measured and true values. The greenness of the developed UV spectroscopic method was evaluated using the Green analytical procedure index (GAPI), Blue applicability grade index (BAGI) and the AGREE tool, confirming compliance with green analytical chemistry principles. The method was developed and validated in accordance with the International Council for Harmonisation (ICH) guidelines for pharmaceuticals for human use. The validation parameters demonstrated satisfactory performance characteristics. The proposed method was successfully applied to the quantitative analysis of rizatriptan benzoate.

This study outlines the development and validation of a simultaneous-equation method (Vierordt’s method) utilizing ultraviolet spectroscopy for the simultaneous estimation of ferulic acid and carnosic acid in bulk drugs. The technique assesses absorbance at 215 nm for ferulic acid and at 284 nm for carnosic acid. The method exhibited goodness of fit in the calibration curve in concentration ranges of 2–14 μg/mL for ferulic acid and 100–700 μg/mL for carnosic acid, with correlation coefficients of 0.9956 and 0.9976. Simultaneous equations for calculating the concentration of ferulic acid and carnosic acid in unknown samples were  C_{Fer =} [A₂(0.000529)–A₁(0.000825)]/(–0.0000289) and C_{Carn =} [A₁(0.059398)–A₂(0.038129)]/(–0.0000289), where A₁ and A₂ are the absorbance of the unknown sample solution at 215 and 284 nm, respectively. The recovery of ferulic acid and carnosic acid using the spiking method was 98–102%, indicating the method's accuracy for quantitative estimation. The observed recovery values in the presence of excipients and phytochemicals remained within the 98–102% range, with RSDs < 2%, confirming the method's specificity. Precision experiments demonstrated RSD values of < 2%, signifying exceptional repeatability and negligible intra- and inter-day variability. The %RSD for ruggedness and robustness validation was less than 2%, indicating that the developed method remained unaffected by equipment changes, inter-analyst variability, and small wavelength variations. The limits of detection (LOD) and limits of quantification (LOQ) for ferulic acid were 0.558 and 1.69 µg/mL, respectively, whereas the LOD and LOQ for carnosic acid were 37.31 and 113.06 µg/mL, respectively, demonstrating greater sensitivity for the detection and quantification of ferulic acid and carnosic acid. The developed simultaneous equation method achieved 101.2 and 100.69% accuracy in the simultaneous estimation of ferulic acid and carnosic acid in bulk samples.

Galantamine hydrobromide (GHB) is an anti-Alzheimer’s drug and a reversible acetylcholinesterase inhibitor. Two simple, sensitive and stability-indicating ultraviolet (UV) spectrophotometric methods were developed and validated for the determination of GHB in pharmaceuticals and a spiked human urine sample. In Method A, the absorbance of the GHB solution in 0.1 M acetic acid (HOAc) was measured at 293 nm. The drug exhibited the same absorbance maximum in 0.1 M hydrochloric acid (HCl), which served as the basis for Method B. Good linearity was ensured over the concentration range of 0.8–80 µg/mL GHB, with correlation coefficients of 0.9807 and 0.9988 for methods A and B, respectively, and the corresponding limits of detection were 0.1477 and 0.3082 µg/mL, while the limits of quantification were 0.4476 and 0.9340 µg/mL, indicating high sensitivity. The Sandell sensitivity values were calculated to be 0.1208 µg/cm² for method A and 0.1175 µg/cm² for method B. Accuracy and precision studies showed low relative error, and %RSD values were below 2%. Robustness was confirmed by deliberate variation of the analytical wavelength by ±2 nm without significant changes in absorbance, while ruggedness studies demonstrated consistent results across different analysts and instruments. Assay of tablet formulations using the standard-addition method yielded the mean percentage recoveries of 98.45 and 100.31% in methods A and B, indicating excellent selectivity. The successful application of the proposed methods to a spiked human urine sample confirmed their biological applicability. Forced degradation studies established the stability-indicating nature of the methods, revealing significant degradation under acidic conditions and good stability under thermal stress, which was further supported by observations in FTIR spectral analysis. The developed methods are rapid, cost-effective and reliable, making them suitable for routine quality control and therapeutic monitoring of GHB.