The direct matrix elements of the energy operator for the npn′h and np5n′h configurations are determined taking into account the spin–other-orbit interaction. Direct matrix elements, together with exchange ones, are intended for further numerical calculation of fine structure parameters and other characteristics of atoms, such as gyromagnetic ratios. The coefficients for radial integrals are calculated in the singleconfiguration approximation, in the formalism of irreducible tensor operators, and in two representations: LSJM and the representation of unrelated moments. A formula has been derived for calculating the direct matrix elements of the considered configurations in the representation of unrelated moments. It has been carefully tested on small rank matrices with M = ±7 (1 rank) and M = ±6 (4 rank). The calculation of all other direct matrix elements has been performed for a matrix with M = 0 (12 rank). The values obtained have been transformed into the LSJM-representation using the matrix of Clebsch-Gordan coefficients and compared with an independent calculation in the LSJM-representation. The complete agreement of direct matrix elements of the interaction considered in two different calculation schemes indicates the reliability of the results obtained. 

As part of research on the development of sonoluminescent spectroscopy, atomic and ionic singlebubble sonoluminescence of dysprosium was first recorded in the mode of bubble movement in a standing ultrasonic wave in a colloidal dodecane suspension of SiO₂ nanoparticles containing DyCl₃. In the spectrum of this sonoluminescence with a resolution of ∆λ = 1 nm, the Dy, Dy⁺ lines in a region of 350–450 nm were recorded together with the molecular SiO lines, due to the entry of nanoparticles into the bubble during sonolysis of the suspension and subsequent collisional excitation of emitters in the bubble plasma. At a spectral resolution of ∆λ = 10 nm, Dy3⁺ luminescence bands with maxima at 477 and 570 nm, which appear by the same excitation mechanism, were recorded. By comparing the experimental and temperature-dependent calculated spectra of Dy, Dy+, the electron temperature of T_e = 7000±300 K was found in the nonequilibrium plasma that occurs during bubble collapse, where dysprosium atoms and ions emit light. 

Thin films (~100 nm) of hetero-ligand complex compounds of terbium(III) with 3,5-dieethyloxybenzoic, 2,5-dimethyloxybenzoic, 3,4-dieethyloxybenzoic acids and phenanthroline as well as a uniform ligand complex of terbium(III) with 3,4-dieethyloxybenzoic acid, have been obtained. Using the data of electron and optical microscopy it has been found that during the process of film formation, the complex crystallizes. With the aim of improving the quality of a film surface, the complexes have been doped to a polymer matrix of poly-N-vinylcarbazole with the weight ratios from 1:1 to 10:1. On the basis of the dependence of the integral intensity of film luminescence on the weight ratio of components in it and also on the basis of kinetics of film luminescence, the assumption has been made about the polymer participation in excitation of luminescence of complexes in the film. 

The spectral and generation parameters of coumarin class dyes and the mechanism of formation of their inclusion complexes (IC) with β-cyclodextrin (β-CD) have been studied. The formation of ICs is accompanied by a significant shift in the absorption and fluorescence spectra. Based on quantum-chemical calculations and the assignment of absorption bands in the IR spectra, the mechanism of complex formation of coumarins with β-CD has been established. It is shown that the studied ICs of coumarins with β-CD are characterized by a higher generation efficiency and photostability and can be considered as new active media for tunable dye lasers, the generation efficiency and photostability of which are higher than those of the initial dyes. 

The values of the zone fluctuation potential (ZFP) in quantum wells located in the space charge region (SCR) of the p-n junction and the lateral ZFP in quantum wells outside SCR in blue, green, and ultraviolet LEDs based on nitrides have been experimentally determined. By the example of green LEDs, it has been shown that the low external quantum efficiency (EQE) of LEDs at the maximum correlates with an increase in ZFP and disordering of heteroboundaries in quantum wells located in SCR. The decrease in EQE at the maximum is caused by the capture of charge carriers by charged centers localized at disordered heteroboundaries. The value of the lateral ZFP in quantum wells located outside SCR is the main parameter that determines the decrease of EQE from the moment of opening the p-n junction to current densities of 30—40 A/cm². 

The optical properties and electronic characteristics of X-ray amorphous and polycrystalline Al4Sm alloy films obtained by vacuum thermal evaporation were studied. The optical constants were measured by the Beattie ellipsometric method in the range of 0.248–7.002 µm. From the spectral dependencies of optical constants, the dispersion dependences of the light conductivity σ, reflectivity R, imaginary and real parts of the dielectric permittivity ε₁ and ε₂ and functions of characteristic energy loss of electrons Im(ε)^–1 were calculated. The effect of the crystal structure of the alloys on the features of their optical spectra was shown. Based on the results of measurements in the infrared region of the spectrum, the electronic characteristics of these alloys were calculated using the two-band conductivity model. 

By the method of high-frequency pulse-periodic (f ~ 8–10 kHz) laser action with a wavelength of l = 1.064 μm and a power density of q = 36 MW/cm2 on Y_0.1Sr_0.9CoO_3–x ceramics at a pressure in the vacuum chamber of p = 2 × 10⁻² mm pt. nanostructured thin films on a silicon substrate have been obtained. The morphology of the obtained films has been studied using atomic force microscopy. The features of the transmission spectra in the visible, near and mid-IR regions have been revealed. An analysis of the electrical properties of the Y_0.1Sr_0.9CoO_3–x structure has been carried out. 

Optimization of the fluorescence enhancement factor of the conjugate of immunoglobulin G labeled with fluorescein isothiocyanate (IgG-FITC) as an immunofluorescent marker was carried out depending on the optical and topographic parameters of a colloidal silver film on the surface of a standard polystyrene plate for immunoassay. Factors influencing fluorescence enhancement were identified. Using time-resolved spectroscopy, analysis of fluorescence excitation spectra, and enzyme immunoassay determination of the relative concentrations of IgG-FITC adsorbed on the solid phase, it was shown that fluorescence enhancement is a plasmon-resonance process. The most important parameter correlated with the fluorescence enhancement factor is the optical density of silver colloidal film at the excitation and emission wavelengths of IgG-FITC. The maximum enhancement factor of 10.2 times was obtained for silver films with the highest optical density. 

Thermoluminescence spectra in the temperature range from 80 to 300 K were compared for lithium fluoride nanocrystals and crystals. It was shown that four and one bands are observed in the spectra of nanocrystals and crystals, respectively. Thermoluminescence intensities integrated over the spectrum and temperature range were measured for two types of lithium fluoride samples, in one of which it is possible, and in the other it is impossible to form radiation color centers with new properties. It was found that in the samples of the first type the intensity is significantly higher. 

The possibility has been experimentally shown of obtaining light sources based on commercial blue LEDs and two narrow-band nanocrystalline phosphors (CsPbBr₃ and CdSe/CdZnS), which simultaneously satisfy the following criteria: the maximum of the emission spectrum corresponds to the peak of human vision sensitivity at night (505 nm), color coordinates in the CIE 1931 standard are close to the point [0.33; 0.33], the correlated color temperature CCT » 6000 K with the possibility of moving to warmer light with CCT » 4500 K, and the full range of possible colors (gamut) exceeds the norms of the HDTV standard, approaching to the UHDTV standard. It is noted that for serious progress in the development of lighting sources adapted to human night and twilight vision, it is necessary to develop metrological standards and corrected units of brightness and luminous intensity while refusing to use the color rendering index for night and twilight lighting. 

The parameters of chlorophyll a (Chl a) fluorescence of the primary leaves of 7-day-old barley seedlings under the impact of elevated temperature (40°C, 3 h) and water deficit (45 h in 3% PEG 6000) were studied. It was shown that the potential and effective quantum yields of photochemical reactions of photosystem II, the photochemical (qP) and non-photochemical (qN) quenching of Chl a fluorescence did not change significantly under these stress factors. High stress sensitivity was found for the coefficient of energydependent quenching of Chl a fluorescence (qE), related linearly with the magnitude of the H⁺ gradient across the thylakoid membrane. Since the qE value is an integral indicator dependent on the light and dark photosynthetic reaction, it is proposed to use this parameter as a marker of the stress state in the photosynthetic apparatus. 

A ground-based spectroscopic method for determining CCl₃F content from measurements of IR-spectra of solar radiation using an IFS-125HR Fourier Spectrometer (FTIR method) is considered. The detector based on mercury-cadmium-tellurium (HgCaTe), which is used for measurements in the CCl₃F absorption spectral region, is cooled by liquid nitrogen. When the vacuum gradually deteriorates in the metal Dewar vessel of the receiver during cooling, the amorphous ice film grows on the detector. The spectral absorption band of amorphous ice at liquid nitrogen temperatures overlaps the CCl₃F absorption band, and the ice film thickness variability adds additional uncertainty to the estimates of the CCl3F atmospheric content. To eliminate this uncertainty, a technique has been developed to estimate the thickness of the ice film and to account for its spectral absorption in the algorithm of solving the reverse problem. The technique has been applied when measuring the atmospheric concentration of CCl3F in 2017—2019 over the NDACC station, St.Petersburg. The results have been compared with ones obtained earlier using a technique in which the thickness of the ice film was adopted by an unknown parameter specified in the process of solving the inverse problem. The previously obtained CCl₃F atmospheric content has been refined using the proposed technique; the difference reaches 10%. 

The infrared absorption spectra of saturated vapors of propyl alcohol isomers and mixtures of these isomers have been studied. A method has been developed for the quantitative determination of the isomeric composition of liquid mixtures of propyl alcohol isomers on the absorption spectra of their vapors in the range of 1.3–1.5 μm. For the analysis of experimental data, the method of multiple linear regression has been used. Much attention has been paid to cleaning the spectra from the interfering effect of atmospheric water vapor, for which the correlation method has been used. The developed method of correlation purification of the spectrum of the substance under study from the influence of the spectra of interfering substances may be of interest not only at the analysis of the composition of alcohol mixtures, but also in other cases when the experimental conditions do not allow the optical channel to be freed from the impurity of interfering substances. 

Recovery of fluorophore groups in dissolved organic matter using the PARAFAC canonical tensor decomposition of fluorescence excitation-emission matrix (EEM) is widely used in the study of natural waters. However, fitting the PARAFAC model, especially for its validation, is very time consuming. Several strategies for accelerating the PARAFAC fitting to the EEM of sea waters were considered. It was shown that strategies with optimization of a large set of hyperparameters do not result in significant acceleration due to high time costs for this operation. It was proposed to perform optimization for one variable once for several iterations of the algorithm. This approach made it possible to achieve acceleration of calculations using line search strategy. The maximum acceleration by 2.3 times was achieved for the line search strategy using the extrapolation step in a power function of the iteration number, although in this case, sequential steps are collinear at some stages of the algorithm. 

It is shown that, despite the complex mechanism of formation of the excited state, the chemi- and bioluminescence spectra, like ordinary diffuse fluorescence spectra, contain information about the magnitude of the purely electronic (vertical) transition of emitting molecules and the degree of homogeneity of their ensemble. The purely electronic transition, as in the case of ordinary diffuse luminescence spectra, is located significantly, almost a half-width of the band, shorter than the maximum of the fluorescence spectrum. An example of the separation of overlapping spectra using the position of the short-wavelength pure-electronic transition is given. 

The uncooled air-bridge photodetectors based on InAs/InAsSbP heterostructures are presented for the mid-IR spectral region. The main difference in the air-bridge design is that a contact pad is outside the photosensitive mesa and is connected with it only by an air-bridge contact. This design makes it possible to reduce the area of the p-n junction, and, accordingly, the capacity of the device. This leads to an increase in the speed without loss in detectivity. The InAs/InAsSbP heterostructures were grown on InAs substrates with the orientation of (111) by MOCVD. The developed photodetectors had a maximum spectral sensitivity in the range of 2.8–3.1 mm and a differential resistance in zero offset of R₀ = 1.0–5.6 kOhm. The capacity of the best devices was C = 3.4–3.6 pF at U_rev = 0 V. The speed of the photodetector using an InGaAsP/InP laser with a wavelength of 1.55 mm was carried out. Determined by the front growth of the photoresponse, the speed is 200 ps. The developed air-bridge photodetectors can be applied to register laser pulses in the range of 1.1–3.8 mm. 

A method is proposed for determining the accumulation time and concentration of triplet molecules in frozen solutions of organic compounds. This method is based on measuring the change in the intensity of phosphorescence for a given change in the intensity of photoexcitation. A comparison of the values of these quantities, determined by the known method on the ignition and attenuation kinetics of phosphorescence and the proposed method, is carried out. Their good agreement is shown and the advantages of this method are noted. 

The purpose of the current study was to evaluate the interaction between zinc ions and horseradish peroxidase (HRP) by ultraviolet-visible, fluorescence, circular dichroism, and FTIR spectroscopies. HRP conformation analysis revealed a noticeable decrease in α-helix from 47% for the free enzyme to 17% for HRP–Zn²⁺ and a reduction in tertiary structures of the enzyme through a Zn²⁺ interaction. Moreover, the fluorescence intensity of HRP was decreased significantly by Zn²⁺. The linear relationship of HRP emission data and inhibitor concentration indicated that the extinction process is linear and occurs uniformly with increasing Zn²⁺ concentration. The values of K_q for the zinc and HRP interaction were in the order of 1011 l/mol, which means that HRP fluorescence was quenched by Zn²⁺ through a static quenching mechanism. 

A rapid identification method for flue-cured tobacco quality was proposed based on Raman spectroscopy. Considering the critical quality factors of flue-cured tobacco-like oil content, softness, and glossiness, four statistical methods, random forest, K-nearest neighbor, logistic regression, and partial least squares, can effectively improve the accuracy of quality identification. We randomly collected 149 flue-cured tobacco samples from multiple producing areas in China. After Raman spectroscopy analysis, Savitzky–Golay convolution smoothing and multi-scatter correction were done. The functional groups were analyzed to select characteristic peaks as features for discriminant analysis. The results show that the Raman spectroscopic information can distinguish the quality of flue-cured tobacco with an accuracy greater than 95%, whereas the partial least-squares approach delivers an accuracy of 100%. We conclude that Raman spectroscopy can be considered a vital avenue for identifying the quality of flue-cured tobacco. 

Time and polarization resolved optical emission spectroscopy of laser-produced plasmas formed on Al alloys has been studied in the visible spectral range at a background air pressure of 10⁻⁴ mbar. A comparative experimental investigation has been made between the results obtained from the polarization-resolved laser-induced breakdown spectroscopy (PRLIBS) and those obtained for the unresolved case (denoted simply as LIBS here). The spectral signal-to-background ratio (SBR) is increased significantly for PRLIBS compared with LIBS for the Mn emission line at a wavelength of 415 nm, which had trace concentrations in the sample. The results have been interpreted within the framework of radiatively recombining plasma where free electrons are captured by ions to emit radiation. In addition, the degree of polarization is quantified for two matrix lines, namely Al⁰ (at 396.15 nm) and Al²⁺ (569.6 nm) by using neighbouring unpolarised emission lines. The plasma parameters are measured and compared with the degree of polarization to determine the dominant mechanism for the polarised emission. Thus, from these results, we feel confident that PRLIBS is a useful and simple addition, capable of improving experimental LIBS performance. 

Laser-induced breakdown spectroscopy (LIBS) was applied for qualitative and quantitative analysis of gold alloys. A frequency double-pulsed Nd:YAG laser was used to generate plasma on the surface of gold alloys. The plasma temperatures of gold and copper were calculated using Boltzmann plots whereas electron number densities were determined via Saha–Boltzmann equations. The effect of self-absorption in the laserinduced emission spectra was evaluated for correction in the intensity of spectral lines. By combining electron number density conservation approach (ENDC) with LIBS, an algorithm for gold alloys composition determination was derived by matching the theoretically derived ratios of the number densities and the experimentally obtained ratios of the number densities extracted from LIBS spectra. The results of ENDC-LIBS approach were compared with those estimated by a conventional calibration-free LIBS approach and other established analytical technique energy dispersive X-ray. The results clearly demonstrated that ENDC-LIBS methodology appeared to be very promising for analysis of LIBS spectra of gold alloys. 

The purpose of this study was to investigate the photoluminescence properties of Bi³⁺-activated Sr₃B₂O₆. Pure Sr₃B₂O₆ and Bi³⁺-doped Sr₃B₂O₆ were synthesized by a solution combustion method. The phase and photoluminescence analyses of the borates that were synthesized were determined by using X-ray diffraction and a spectrofluorometer respectively at room temperature. It was observed that the synthesized Bi³⁺-doped Sr₃B₂O₆ emitted blue light (441 nm) upon excitation with 366 nm. Finally, the Stokes shift of Sr₃B₂O₆:Bi³⁺ was calculated and found to be 4646 cm^–1. 

The effect of adding PbF₂ to the spectroscopic properties of dysprosium-doped borate-based glasses is studied. The content of PbF₂ in the glass is varied from 0 to 50 mol%. X-ray diffraction confirms the amorphous nature of the glass. The Judd–Ofelt theory is applied to evaluate the intensity parameters Ω_λ (λ = 1, 2, 3) from the UV-Vis-NIR absorption spectra of glasses. Various radiative parameters are calculated, and the variation of these parameters with different concentrations of lead fluoride is discussed. The fluorescence spectra of glasses are recorded, and it is observed that the fluorescence yield increases as the PbF₂ content rises from 0 to 40 mol% but decreases thereafter. The IR absorption spectra of these glasses are also recorded and interpreted in terms of changes in the structure of the glasses. The decay lifetime of the ⁴F_9/2 level of the dysprosium ion is measured from the decay profile and compared with the calculated lifetime. 

Lithium (2 wt %)-doped cadmium oxide (CdO:Li) film was grown on a glass substrate via a sol-gel processed screen-printing set-up. Through X-ray diffraction, it was demonstrated that the CdO:Li film exhibits reflections from the (111), (200), (220), (311), and (222) CdO cubic phase planes. The SEM image showed irregularly shaped, interconnected, and agglomerated grains on the entire film. The optical diffuse reflection study revealed that the film has a direct transition of the band gap at 2.50 eV. The refractive index of the film varies with photon energy and gains maximum value (~2.3) at 1.5 eV. The electrical attributes of the film were inspected by Hall measurement. It was noticed that the film conveyed n-type conductivity with low resistivity of the order of 10^–3 Ω × cm.

Pure CdO and TiO₂-doped CdO nanocomposites with different wt% ratios (0.1, 0.3, and 0.5%) were prepared by a simple solution method. Structural, morphological, and elemental composition of the prepared samples was undertaken by X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray analysis, and photoluminescence. The diffraction peaks of the samples showed the cubic phase structure and the prepared nanocomposites were on the nanoscale. SEM revealed the plate-like chunks with irregular grains due to agglomeration. The particle size of the pure CdO sample was found to be 61.98 nm, whereas TiO₂-doped CdO (0.1, 0.3, and 0.5%) exhibited 49.57, 35.41, and 31 nm. The first peak was observed at 1.90 eV in the IR-visible region and the second peak at 2.38 eV. Both the peaks correspond to CdO. Near-band-edge emission of 2.38 eV is typical for both pure and doped CdO. It can be suggested that the photo-generated electrons have been trapped in to Ti⁴⁺ in the forbidden gap, which enhanced the deep level emission. 

Dynamics of the laser driven electron plasma waves (EPWs) in plasmas with axial density ramp has been investigated theoretically. The effect of self-focusing of the laser beam on the power of laser excited EPW has been incorporated. During its propagation through the plasma, the laser beam excites an EPW at frequency ω_ep that due to the optical nonlinearity of plasma gets nonlinearly coupled to the laser beam. Using variational theory semi analytical solutions of the coupled nonlinear wave equations for the pump wave and EPW have been obtained under W.K.B. approximation technique. It has been observed that power of the EPW is significantly affected by the self-focusing effect of pump beam. 

Generation of coherent terahertz (THz) radiations by nonlinear interaction of a pair of coaxial q-Gaussian laser beams with underdense plasma has been investigated theoretically. Owing to the relativistic increase in electron mass under the intense fields of the laser beam, the resulting optical nonlinearity of plasma leads to cross focusing of the laser beams. Because of the nonlinear interaction between the two laser beams, the oscillations of plasma electrons also contain a frequency component at beat frequency and thus generate a nonlinear current density at frequency equal to the difference of the frequencies of the incident laser beams. This nonlinear current density acts as a source for coherent THz radiations. Starting from the nonlinear Schrodinger wave equation a set of coupled differential equations governing the evolution of beam widths of the laser beams and intensity of generated THz radiations with longitudinal distance has been obtained with the help of variational theory. The equations obtained in this way have been solved numerically to envision the effect of laser as well as plasma parameters on the intensity of generated THz radiations. 

Coal spontaneous combustion (CSC) has been a global hazard for decades, causing significant losses. Hydrocarbon gases, including carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), ethylene (C₂H₄), acetylene (C₂H₂), and oxygen (O₂), have proved to be good inhibitors for forecasting CSC. However, the cross-interference and absorption spectrum overlaps prevent their practical applications. This study simulates the refined distribution of the absorption lines of these index gases in the infrared spectral range to solve these problems. By selecting the optimal absorption lines for each gas, their detection performance was experimentally tested, and the results were analyzed using the Allan variance method. The results reveal that the optimal absorption lines are centered at 1566.64, 1572.32, 1653.72, 1626.34, 1530.37, and 760.65 nm for CO, CO₂, CH₄, C₂H₄, C₂H₂, and O₂, respectively. Relative detection errors are 0.62, 0.51, 3.06, 4.20, 0.58, and 1.96%, and the detection limits are 3.47×10⁻⁶, 4.56×10⁻⁶, 0.53×10⁻⁶, 2.85×10⁻⁶, 0.33×10⁻⁶, and 1581×10⁻⁶, respectively. The detection sensitivity and comprehensive detection accuracy were significantly improved. This study will provide a basis for solving the problem of the cross-aliasing interference between index gases for bituminous CSC. 

To tackle the cross-interference problem between CH₄ and C₂H₄ and the aliasing interference problem of C₂H₄ itself, on the basis of the sparse decomposition theory, multiple Lorentz function-based methods were proposed for separating the cross-aliasing interference of near-infrared (IR) C₂H₄ absorption lines. A quadruple Lorentz function-based separation model describing the absorption coefficient of C₂H₄ is developed, with which the absorption lines of background gas and to-be-measured C₂H₄ were separated from the absorption lines of mixed gas, thereby effectively separating the absorption line of C₂H₄ and accurately measuring its concentration. The results show that the maximum errors of C₂H₄ and CH₄ gasometrical analyses are 5.3×10⁻⁶/201.7×10⁻⁶ and 57×10⁻⁶/5000×10⁻⁶, respectively. The proposed method effectively eliminates the errors caused by cross-aliasing interference of C₂H₄ absorption lines in the near-IR bands and improves the detection accuracy of the TDLAS gas detection system. The findings of this study provide a feasible solution to the cross-aliasing interference problem of IR absorption lines. 

We optically characterized agar, muscle, and Zerdine phantoms mimicking human tissues. To the best of our knowledge, optical parameters for agar, muscle, and Zerdine phantoms have not been optimally determined in the literature. For this reason, this novel study makes significant contributions to the literature and there is an important innovation and originality in the optical characterization of these materials. With this research based on the phantoms, in this article we make important contributions to possible future studies, including optical device design and imaging technique development, system validation studies, etc. In other words, characterization studies on materials that imitate tissue in light-tissue interactions can provide important information to researchers and practitioners. In optical characterization, basic parameters such as the absorption coefficient, reduced scattering coefficient, and anisotropy factor, are evaluated as distinguishing characteristics, and these are referred to as microscopic optical properties in the literature. In this study, the optical properties of the aforementioned three different phantoms were experimentally investigated and compared with each other’s. First, the macroscopic optical properties of the phantoms, including the absorbance, transmittance, reflectance, refractive index, and attenuation coefficient, were measured using a single integrated sphere and a spectrometer equipped with a broadband white light source within the wavelength range 200 to 1000 nm. Then, using the Kubelka–Munk function method, microscopic optical properties, which are the absorption coefficient, scattering coefficient, and reduced scattering coefficient, were determined based on the data of these macroscopic properties. 

The goal of the present investigation was to develop and validate the UV-spectrophotometric technique for the quantitative estimation of ripasudil hydrochloride hydrate in pure and ophthalmic formulations. Ripasudil hydrochloride hydrate is a novel drug molecule that has been used to treat glaucoma and ocular hypertension. It was licensed for therapy in Japan for the first time in September 2014. Until now, only an HPLC analytical method for determining it in dosage forms and biological fluids has been disclosed. The objective of this research was to screen a solvent system in which ripasudil hydrochloride hydrate can be completely solubilized, then develop and validate a simple, accurate, precise, and cost-effective UV-spectrophotometric method for estimating ripasudil hydrochloride hydrate in the pure and ophthalmic formulations in accordance with International Conference on Harmonization (ICH) recommendations. The current method is simple, quick, accurate, precise, and cost-effective. Ripasudil hydrochloride hydrate is soluble in HPLC-grade distilled water, so it was used as a solvent to form the solution. The subsequent solution was scanned within the UV range (200–400 nm). The λ_max of ripasudil hydrochloride hydrate was found to be 278 nm. Beer’s law is valid within the 10 to 50-µg/mL concentration range. The developed analytical approach was extensively validated as per ICH guidelines for linearity, accuracy, precision, robustness, detection limit, and quantitation limit. Linearity was obtained within the 10 to 50 µg/mL range with a correlation coefficient of 0.9981. Limit of detection and limit of quantitation were found to be 0.0785 and 0.2355 µg/mL. The technique presented good recovery and reproducibility; thus, the proposed technique might be employed for regular investigation of ripasudil hydrochloride hydrate in the pure and ophthalmic formulations. 

The present paper explains the development and validation of four new eco-friendly and stabilityindicating spectroscopic methods of estimating a calcimimetic drug, i.e., cinacalcet hydrochloride (CIN), in its different pharmaceutical formulations. In these methods, the response of the standard solution is measured in 0.1N HCl as a diluent (nonhazardous) at 279, 294, and 299 nm for UV, first-, and second-order derivative spectrophotometric tools, respectively. The AUC-spectrophotometric technique is carried out by calculating the area under the curve (AUC) between the wavelength regions ranging from 266 to 286 nm. The linearity graph of the methods is plotted by taking response [Absorbance/(dA/dλ)/(d²A/dλ²) or AUC] values against the concentration and shows that the drug obeys Beer’s law within the concentration range 2.5 to 200 μg/mL for all the methods. The drug is exposed to various stress conditions as recommended by the ICH Q1A-Q1E guideline. The different method validation parameters are within the acceptable limit as per the ICH Q2R(1) guideline. The greenness profile of the developed UV spectroscopic tools is evaluated using the National Environmental Methods Index, the Analytical Eco-Scale, and the Analytical GREEnness (AGREE) metric approach. All approaches prove the greenness of the methods concerning solvent, chemicals, energy consumed, and waste produced. Eco-friendly spectroscopic methods can determine the quantity of CIN in various pharmaceutical dosage forms without influencing the environment and analysts. 

A simple, accurate, and cost-efficient UV-Visible spectrophotometric method has been developed for the determination of naphazoline nitrate (NPZ) in pure and pharmaceutical formulations. The suggested method was based on the nucleophilic substitution reaction of NPZ with 1,2-naphthoquinone-4-sulfonate sodium salt in alkaline medium at 80ºC to form an orange/red-colored product of maximum absorption (λ_max) at 483 nm. The stoichiometry of the reaction was determined via Job’s method and limiting logarithmic method, and the mechanism of the reaction was postulated. Under the optimal conditions of the reaction, Beerʼs law was obeyed within the concentration range 0.5–50 μg/mL, the molar absorptivity value (ε) was 5766.5 L × mol^–1 × cm^–1, Sandellʼs sensitivity value was 0.0474 μg/cm², the limits of detection and quantification were found to be 0.2154 and 0.6529 μg/mL, respectively. The formation constant of the complex was calculated by using the Benesi–Hildebrand equation. The suggested method was successfully applied for the quantification of NPZ in pharmaceutical formulations with good accuracy and precision. Therefore, this method can be applied for routine analysis of naphazoline. 

A fluorescence quantitative detection method suitable for high-throughput screening of rhamnosidase catalytic activity on naringin was established. Detection of prunin at λ_ex/λ_em = 360/450 nm was based on the fluorescence difference after heating under alkaline conditions. Detection of naringin at λ_ex/λ_em = 325/400 nm was based on the difference in fluorescence in phosphate buffer. The method is suitable for prescreening many samples. A similar method can detect the fluorescence of hesperidin and hesperitin-7-o-glucoside, which provides a reference for the rapid detection of diglycosides and corresponding deglycosylated monoglycosides.