The influence of peripheral substitution and the nature of the macroheterocyclic heteroatoms on the basicity of hydrophilic 5,10,15,20-tetraarylporphyrins in the lowest excited singlet S₁ state has been studied using absorption and fluorescence spectroscopies. It has been established that in the proper porphyrins, the basicity of the lowest excited singlet S₁ state decreases compared to the ground S₀ state, and the difference in the basicity constants рK_a depends on the nature of electronic communication between the macrocycle and peripheral substituents. In case of the inductive effect of substituents, the difference in the basicity constants рK_a is small, while mesomeric effects lead to significant differences in рK_a values. It has been shown that the cooperative nature of protonation, leading to almost simultaneous addition of two protons, is preserved in both cases. It has been established that the replacement of the pyrrole fragment with the thiophene one in the macroheterocycle leads to a decrease in cooperativity both in the ground S₀ and in the lowest excited singlet S₁ states. It has been found that in S₁ state the basicity constants characterizing the addition of the second and the third protons by thia-substituted porphyrin differ significantly (рK_a2 - рK_a3 = 2), while in the ground state they are close. The activation entropy change ΔΔS‡ upon protonation of porphyrins in the lowest excited S₁ state compared to that in the ground S0 state has been determined.

The photophysical properties and efficiency of photosensitized singlet oxygen formation by mesotetrakis(4-N-methylpyridyl)porphyrin in a complex with hydroxyapatite nanoparticles were studied. It was shown that, on surface of hydroxyapatite nanoparticles, at least three types of complexes, characterized by different access of oxygen to porphyrin molecules, are formed. It was found that the rotation of the pyridyl substituents of porphyrin in the complex with hydroxyapatite nanoparticles is significantly hindered, while the porphyrin molecules on the surface of the nanoparticles locates in a less polar environment compared to water. The decrease of the quantum yield of the photosensitized singlet oxygen formation by at least 9 times is observed for the porphyrin in the complex with hydroxyapatite nanoparticles. It has been established that the decreasing of the pH to less than 5.0 (pH < 5.0) promotes the release of the porphyrin from hydroxyapatite nanoparticles, while the efficiency of singlet oxygen formation increases, although it does not reach the values characteristic for free porphyrin.

The spectral and luminescent properties of the styryl derivative of thioflavin T (ThT) – 2-{(1E,3E)-4-[4- (dimethylamino)-2,6-dimethylphenyl]buta-1,3-dien-1-yl}-3-ethyl-1,3-benzothiazolium-3 tosylate – have been studied (Th-C23). It has been established that the kinetics of fluorescence decay of Th-C23 when incorporated into amyloid fibrils (AF) is not exponential and can be represented in the form of a unimodal distribution of fluorophores over duration α(τ). It has been shown that ThT and Th-C23, when incorporated into AF structure, form an effective donor-acceptor (D-A) pair. Despite the energy transfer, the polarization degree of the acceptor fluorescence has high values (~0.4) within the entire spectrum, which is explained by the special orientation of D-A pairs: parallel and antiparallel. Based on measurements of the fluorescence spectrum of the donor (ThT) and the absorption spectrum of the acceptor (Th-C23), the critical energy transfer radius R₀ has been calculated, which can take values from 54 to 68 Å depending on the mutual orientation and quantum yield of the donor and acceptor.

The bactericidal components of air plasma jets generated by a direct current glow discharge and a dielectric barrier discharge were studied using IR and UV absorption spectroscopy. The mole fractions of bactericidal components with a band structure of the absorption spectrum were determined by selecting a mole fraction value in the calculated spectrum that ensured compliance with the experimental spectrum. The spectra were calculated using the Hitran spectral database and the Specair 3.0 program. The error in mole fractions due to the violation of the Bouguer–Lambert–Beer law when using absorption coefficients convolved with the instrumental function was determined. The mole fractions of bactericidal components with a continuous absorption spectrum were calculated using the Bouguer–Lambert–Beer law in a standard way. It was shown that the methods of IR and UV absorption spectroscopy make it possible to determine the mole fractions for the full set of bactericidal components in air plasma jets of glow and barrier discharges.

The reason for the increase in the transparency of the polymer obtained in the presence of a small addition of molecular iodine in the liquid photopolymerizing composition is satisfactorily explained by the formation of a charge transfer (CT) π,σ-type complexe: oligocarbonate dimethacrylate with molecular iodine. The CT-band (360 nm) absorbs a significant part of actinic radiation, as a result of which the rate of photolytic decomposition of the photoinitiator at the initial stage of polymerization satisfies the condition of the free volume output from the polymer to the liquid part of the photopolymercompozite. At deeper stages the principle of layer-by-layer photopolymerization is realized. This is possible due to the consistent enlightenment of the thin upper layers exposed to UV light.

The excitation spectra and photoluminescence (PL) spectra, as well as the luminescence kinetics of composites based on low-density polyethylene with different contents of CaGa₂S₄:Eu²⁺ were studied. It was shown that the PL intensity is due to the 4f⁶5d→4f⁷ transition of Eu²⁺ ions and maximal at the filler concentration of 7 vol.%. It was shown that the dependence of the PL intensity on the excitation power density up to 0.3 W/cm² is linear, which indicates the possibility of using these phosphors as radiation sources in the visible range of the spectrum for various lighting systems.

Light-accumulating oxide systems HfO₂−ZrO₂ with the duration of afterglow up to 10 min were synthesized by the method of chemical deposition and their spectral-luminescent properties were investigated. It was found that the value of HfO₂:ZrO₂ ratio has a significant influence on the intensity and decay kinetics of visible luminescence of such systems, as well as on the values of the weight coefficients and the positions of individual components of the spectral bands of luminescence and its excitation. The result is explained by the contribution of complex optical centers of titanium impurity in ZrO₂ to the intracenter luminescence of oxygen vacancies in HfO₂ and competing with quenching of luminescence by nonradiative recombination centers.

Using specific examples of recording and processing the spectral-spatial profiles of local diffuse reflection of light radiation by tissues of the human hand, the capabilities of spectroscopy with spatial resolution when determining the optical properties and parameters of the microvasculature of the circulatory system of superficial tissues are demonstrated. It is shown that the greatest contribution to the scatter of the obtained results is made by the heterogeneity of tissue properties caused by individual distribution of vessels and gradients of chromophore concentrations in the investigated point of the body, as well as by poor study of absorption indices of the main chromophores of exsanguinated and dehydrated subcutaneous tissue. The technique of registration of spectral-spatial profiles and their two-stage processing is presented, and its capabilities and disadvantages are discussed. Prospective application of diffuse reflection spectroscopy with spatial resolution in controlling the hydration of superficial tissues in the process of treatment of their inflammation and edema is shown.

The vibrational spectra of ammonium sulfates found in nature are studied: tschermigite NH₄Al(SO₄)₂(H₂O)₁₂, lonecreekite NH₄Fe(SO₄)₂(H₂O)₁₂, ammoniovoltaite (NH₄)₂Fe²⁺ ₅Fe³⁺ ₃Al(SO₄)₁₂(H₂O)₁₈, sabieite NH₄Fe(SO₄)₂, ammonioalunite NH₄Al₃(SO₄)₂(OH)₆ and ammoniojarosite NH₄Fe₃(SO₄)₂(OH)₆, to determine the behavior of ammonium in positions with inappropriate symmetry. The disordering of the ammonium cation in salt crystals was revealed, caused by the need to adjust the tetrahedral cation to the symmetry of the position in order to preserve the symmetry of the crystal. If the symmetry group of the position is not a subgroup of the symmetry group of the tetrahedron, the NH₄⁺ tetrahedron is distorted by the subgroup Hʹ common for T_d and H, where H is the symmetry group of the position. Then, a polyhedron corresponding to the symmetry of the position is constructed from N = |H|/|Hʹ| (|H|, |Hʹ| – the orders of these groups) distorted tetrahedra. The ammonium cation under disordering has several orientations (N), the superposition of which formally gives a polyhedron corresponding to local symmetry. For the given salts, the maximum common subgroups are C_3ν and C₃. The distortion of ammonium leads to activation of ν₁, ν₂ [NH₄⁺] vibrations in the infrared spectrum and splitting of ν₃, ν₄ [NH⁴⁺] but in the case of finding the ammonium in a centrallysymmetrical position, as in ammonioalunite and ammonioarosite, the effect is hardly noticeable. On the contrary, in ammonium alum, ammoniovoltaite, sabeyite the band ν₄ [NH₄⁺] is noticeably split, and vibrations of ν₁, ν₂ [NH₄⁺] are clearly seen in the spectra.

The resonances of free excitons A ~ 1.0409 eV, B ~ 1.0445 eV and C ~ 1.2690 eV are detected in the reflection spectra of single crystals of the direct-gap compound CuInSe2 at temperature of 8.6 K. It has been established that the resolving of these resonances A, B and C can be explained by the removal of degeneracy from the energy levels of the valence band due to the influence of crystal field and spin-orbit interaction in the tetragonal lattice of CuInSe₂ with Δ_CF ~ 5.4 meV and Δ_SO ~ 224 meV. Based on measurements of the temperature dependence of the reflection spectra in the range of 8.6–90 K an effect of increasing the energy position of the resonances of free excitons A and B caused by the deformation of the unit cell (tetragonal stretching) of the CuInSe₂ lattice with a chalcopyrite structure has been discovered. Based on the temperature quenching of the exciton resonances A ~ 1.0409 eV and B ~ 1.0445 eV the binding energy of these excitons has been determined to be 10.7 and 15.2 meV, respectively.

Nickel nanoparticles were synthesized at room temperature by a one-step method of chemical reduction of Ni ions from nickel chloride hexahydrate (NiCl₂ · 6H₂O) using sodium tetrahydride borate (NaBH₄). The microstructure of nanoparticles was studied by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy. Analysis of X-ray diffraction and Raman spectroscopy data showed that the resulting nanoparticles have a cubic structure of metallic nickel with a crystallite size (coherent scattering region) in the range of 3–6 nm. Morphology studies indicate that nickel nanoparticles are spherical in shape and are in contact with each other, forming large agglomerates of nanograins.

A technique was developed to fabricate a new type of hybrid exciton-plasmonic nanostructures consisting of electrostatically deposited laterally oriented silver nanoplates capped with hydrophobic Zn_xCu_yIn_zS₂/ZnS quantum dots layers via Langmuir—Blodgett technique. Pronounced photoluminescence quenching and significant decrease in the emission decay time indicate the development of efficient resonant energy transfer in the resulting hybrid plasmonic nanostructures. To clarify the nature of the emission from these nanostructures we propose the approach based on the comparison of polarization dependences of the emission from quantum dots atop the quartz glass and the silver nanoplates. Our data point toward the scattering by transverse surface plasmons of silver nanoplates indirectly excited through the energy transfer from quantum dots.

As a result of a detailed analysis of the previously discovered effect of the concentration of phosphotungstic acid (PTA) on its reduction in nanocomposite films with poly(vinyl alcohol) (PVA) under the influence of gamma radiation, it was established that the molar absorption coefficient at the maximum of PTA band caused by intervalence charge transfer in the reduced PTA heteropolyanions (HPA), at low PTA concentrations is 8 times higher than at high concentrations. Only 20% of this increase is due to the predominance of two- and one-electron-reduced HPAs at low and high concentrations, respectively. It is concluded that the main reason for the concentration effect is associated with a decrease in the size of PTA nanoparticles with decreasing PTA concentration in the films.

The possibility of surface passivation with selenium for silicon layers hyperdoped with Se was estimated by the X-Ray photoelectron and Rutherford backscattering spectroscopy. Silicon layers hyperdoped with selenium have been formed by Se implantation (140 keV, 6.1 · 10¹⁵ cm^–2) followed by pulsed laser annealing (PLA) (λ = 694 nm, W = 2.0 J/cm², τ = 70 ns). It was found that the Se concentration in the sub-surface region (2.0–2.5 nm) is 0.67% (3.35 · 10²⁰ cm^–3). Such a high concentration of Se can be attributed to the effect of accumulation of these species in the near-surface region during the PLA process. It was shown that Se is solely bonded to Si, Se-O bonds were not formed in the sub-surface region of the implanted layer during PLA. The chosen laser pulse energy density of W = 2.0 J/cm2 has provided achieving the structural perfection (above 91 %) and high concentration of Se at the Si lattice sites (above 69 %).

We have studied the mechanism of photodamage of gram-negative bacterial cells E. coli, sensitized with the indotricarbocyanine dye PK220, when exposed to radiation from a LED source with a wavelength at the emission spectrum maximum λ_max = 745 nm, corresponding to the long-wave absorption band of the dye. To assess the magnitude of the photobiological effect, the intensity of the cells’ own (not enhanced by activator additives) light-induced chemiluminescence has been used. It has been established that immediately after the cessation of cell suspension irradiation, the main contribution to their photodestruction comes from singlet oxygen and, to a lesser extent, from hydrogen peroxide; hydroxyl radicals do not play a significant role in the mechanism of sensitized photochemical processes.

Characteristics of the Nd:YAG multistage optical amplifier of laser beam, the spatial parameters of which are corrected by the thermal lenses formed in the active elements of each amplifier cascade, have been studied. The crystals Nd:YAG pumped by the laser diode units in accordance with the transversal scheme have been used as the amplifier active elements. It has been shown that the removal of lensecompensators allows one to reduce total optical losses of the amplifier and enhance its compactness. At comparable output power levels, the optical losses of an optical amplifier with five amplification stages and correction of the characteristics of the amplified beam by thermally induced lenses of active elements are 16 %, and its linear dimensions are 13 % less than similar indicators for the five-stage amplification system with 4 two-lens compensators between amplification stages.

Two-dimensional (2D) layer materials have illustrated prominent interest with various usages in optoelectronics, nanoelectronics, and solar cells. Numerous physical behaviors of 2D materials have been explored for a category of monolayer transition metal dichalcogenides (TMDCs). These involve molybdenum disulfide (MoS₂), molybdenum diselenite (MoSe₂) and MoSSe janus monolayers that have gained remarkable interest because of their distinguished optoelectronic features. Particularly, the band gap transitions of these TMDC materials undergo from indirect band gap transition to direct one by reducing the dimension from the bulk-counterpart to their MoS₂, MoSe₂, and MoSSe monolayers, respectively. To this end, we conducted a comparative investigation and analysis of the electronic structure behaviors as well as optical spectra of MoS₂, MoSe₂, and MoSSe monolayers. The optical absorption spectra of these 2D-materials are ranging between the infrared (IR) and visible regimes for MoS₂, MoSe₂, and MoSSe sheets and the absorption of light emerges between 1.6 and 1.8 eV, corresponding to their semiconducting character. These 2D-materials are potential candidates for solar cells and optoelectronic applications.

The study investigates the corrosion behavior and microstructural changes in seventeenth-century cast iron cannons exhibited at the Archaeological Museum in Goa. Chipped samples from four cannons underwent analysis for surface morphology, microstructure, and elemental composition using optical microscopy, SEM-EDX, and X-ray diffraction. FTIR spectroscopy was employed to identify the molecular structure of organic compounds, metal oxides, and oxyhydroxides on the surface. The findings reveal that the pearlite matrix of the cast iron contains graphite flakes, leading to a distinctive form of graphitic corrosion on the cannon surface. Highly localized graphitic corrosion areas on the surface have resulted in pits or series of pits, posing a potential risk to the structural integrity of the cannons over time. The study identifies the presence of chloride as a contributing factor to the corrosion process, working in tandem with graphitic corrosion of the cast iron. Understanding these corrosion mechanisms is crucial for developing strategies to ensure the long-term preservation of these historical artefacts.

We present new aspects of erbium or ytterbium doped pure gadolinium oxide (Gd₂O₃:Er³⁺/Yb³⁺) as a suitable candidate for drug delivery and magnetic resonance (MR) applications. The samples were prepared using the conventional sol–gel synthesis technique. The structural studies revealed that the prepared sample was monophased and crystallizes in a cubic structure. FTIR measurements confirmed the creation of Gd₂O₃:Er³⁺/Yb³⁺ phosphor. SEM micrographs clearly indicated that the particles crystallized in uniform shape, exhibiting nano-rod formation, with the particle size ranging from 55 to 5 nm. TEM images revealed that Er³⁺ and Yb³⁺ co-doped Gd₂O₃ nanoparticles were the collection of the nano-rods 2–4 nm thick and 18–20 nm long. Also, photoluminescence analysis of the phosphor samples for variable concentrations of doping ions was presented. When doped with Er³⁺/Yb³⁺, nano-rod Gd₂O₃ emits intense green emission and some red emission peaks, under a 980-nm near-infrared laser. Our study shows that as-prepared samples may be useful for optical imaging systems and that nano-rod formation may be used as a major host carrier for drug delivery.

The synthesis and characterization of Dy³⁺-activated CaSi₂O₅ phosphor is reported. The phosphors were synthesized using a modified solid-state reaction method with variable concentrations of doping ions (0.1–2.5 mol.%) of Dy³⁺. The synthesized phosphors were characterized by X-ray diffraction (XRD) analysis and the field emission scanning electron microscopy (FESEM) technique. The XRD pattern revealed that the doped phosphors had a cubic structure. FESEM micrographs clearly indicated that the particles crystallized in inhomogeneous morphology on a micrometer scale with a sporadic and asymmetrical shape. Photoluminescence excitation and emission spectra were monitored for variable doping concentrations and the emission found at 485 and 576 nm (excited at 353 nm). The corresponding transitions of the doping ion and concentration quenching effect were studied in detail. The 1931 CIE (x, y) chromaticity coordinates (x = 0.30 and y = 0.31) showed the distribution of a spectral region calculated from PL emission spectra. On the basis of CIE analysis, the prepared phosphor is useful for white light emission in inorganic light-emitting diodes. As-synthesized phosphor was examined by thermoluminescence glow curve analysis with different doses of gamma and electron beam and corresponding kinetic parameters were calculated using the computerized glow curve deconvolution technique.

A series of Tb-³⁺doped Li₂CaSiO₄ phosphors were prepared by high-temperature solid-state reaction method. The structural studies were done using the X-ray diffraction (XRD) technique. The XRD patterns revealed that the sample was monophased and crystallizes in a cubic structure. Scanning electron microscopy (SEM) was used to obtain information about the morphology of the prepared samples. SEM micrographs clearly indicated that the particles crystallized in inhomogeneous morphology, with the particle size ranging from 1 μm to 100 nm. Also, photoluminescence (PL) analysis of the phosphor samples for different concentrations of doping ions with variable excitations were presented. The PL excitation spectrum of Tb³⁺ iondoped Li₂CaSiO₄ has many sharp peaks, mainly at 418 нм (⁵D₃→⁷F₅), 436 нм (⁵D₃→⁷F₄), 456 нм (⁵D₃→⁷F₃), 472 нм (⁵D₃→⁷F_2,1,0), 487 нм (⁵D₄→⁷F₆), 550 нм (⁵D₄→⁷F₅) and 590 нм (⁵D₄→⁷F₄), assigned to the transitions of Tb³⁺ ion respectively (excited at 237 nm). The 1931 CIE (x, y) chromaticity coordinates showed the distribution of the spectral region calculated from PL emission spectra, and found to be (0.19, 0.22) in a bluish-green region of Tb³⁺ (0.01 wt (in grams)) Li₂CaSiO₄ phosphor. Our study shows that asprepared phosphor may be useful for optical devices, mainly for LEDs, as a bluish-green component.

Ultraviolet-emitting phosphors with the formula K_2–xPb_xAl₂B₂O₇ (0.0025 ≤ x ≤ 0.03) were synthesized at 850ºC for 6 h in air. The powder X-ray diffraction technique was used to analyze the phases of all prepared borates. The FTIR technique was used to examine the bond structure of K₂Al₂B₂O₇. At room temperature, a spectrofluorometer was used to examine the photoluminescence characteristics of the prepared phosphors. K₂Al₂B₂O₇:Pb²⁺ was found to have emission and excitation bands at 373 and 271 nm, respectively. An extensive investigation was conducted on the correlation between emission intensity and Pb²⁺ content for K_2–xPb_xAl₂B₂O₇. Consequently, 0.01 mol Pb²⁺ was found to be the optimal concentration in K2Al2B2O7. Eventually, it was found that the Stokes shift of the prepared material K₂Al₂B₂O₇:Pb²⁺ is 10,090 cm⁻¹ using the excitation band at 271 nm and the emission band at 373 nm. As a result of this investigation, a brandnew UVA radiation-emitting material has been established.

To achieve consistent color reproduction of printed products and accurate measurement the content of mixed ink has always been an important research topic in the printing industry. This paper proposes a spectral-based method for measuring the content of dual-color mixed printing ink, aiming to solve the difficulty in determining the specific content of the base color in the same ratio of dual-color ink by using spectral analysis. First, a composite filtering method combining median filtering and wavelet transform was compared and selected for spectral preprocessing. Then, three methods, namely the successive projections algorithm (SPA), competitive adaptive reweighted sampling method (CARS), and stable competitive adaptive weighted sampling method (SCARS), were used to extract feature wavelengths from the preprocessed information. Based on partial least squares regression (PLSR), four models, PLSR, SPA-PLSR, CARS-PLSR, and SCARS, were established for predictive analysis. To further test the model, the SCARS-PLSR model was used for predictive analysis of magenta-cyan, yellow-magenta, and yellow-cyan binary samples with a mass fraction ratio of 0.5. The results showed that the SCARS-PLSR model has the best predictive performance, with RMSE and R² values of 0.0052, 0.0002, 0.0004 and 0.9989, 0.9999, 0.9999, respectively. This indicates that this study can accurately determine the content of dual-color ink by spectral analysis.

Aluminum is a widely distributed element and plays an indispensable role in our lives, but excessive intake of Al³⁺ can cause potential harm to human health. Highly selective methods for the rapid detection of Al³⁺ are urgently needed. Here, a novel “turn on” fluorescent probe L based on Schiff-base of 2-hydroxy-1- naphthaldehyde and 8-aminoquinoline was obtained in an excellent yield. Probe L presents significant properties such as rapid response, good stability, wide pH range, simple synthetic operation, and provides an efficient strategy for the highly selective detection of Al³⁺ in an aqueous solution of DMSO/H2O (7:3, v:v). According to Job's curve and fluorescence titration, probe L with Al³⁺ forms a 2:1 ratio of complex, and the lowest limit of detection is 3.23×10−8 mol/L. The possible combination mode for probe L with Al³⁺ was proposed by comparison with the changes of ¹H NMR and FTIR spectra of L and its complex. In addition, the potent applicants for probe L were also investigated, and indicated that it could conveniently be made into a series of sensor strips and applied to rapidly detect trace Al³⁺ in traditional Chinese medicine.

Current challenges in the field of luminescent materials are concerned with the designing efficient material to meet the rapidly rising demands of industry. Luminescent material excitation and emission are highly complex phenomena driven by the combination of atomic-level properties such as valence electron, interatomic radius, ionic radius, etc., and physical properties such as crystal structure, symmetry etc. The current research paper focuses on the development of a machine-learning algorithm based on simple luminescent materials to predict the excitation to the closest possible accuracy using easily accessible key attributes by the CatBoost regressor, multiple linear regression (MLR), and an artificial neural network (ANN) approach. These selected features likely correlate with the excitation of the material. In comparison, the ANN and MLR algorithms have higher mean absolute error values in both the training and test datasets. The CatBoost algorithm outperforms the other algorithms in terms of mean of the absolute percentage difference, achieving a value of 0.302136% in the training dataset. The CatBoost algorithm exhibits the lowest root mean squared error value of 1.680768 nm in the training dataset, indicating that its predictions have a smaller average deviation from the actual values. The style for studying the material property has the potential to reduce the cost and time involved in an Edisonian approach to the lengthy laboratory experiment to identify excitation.

Valbenazine tosylate, a benzoquinolizidine derivative, is a highly selective vesicular monoamine transporter 2 inhibitor. The drug has been approved by the FDA as the first and only approved treatment for tardive dyskinesia. To our knowledge, this is the first report on the development and validation of simple, rapid, sensitive, and cost-effective spectrofluorimetric methods based on the native fluorescence of the drug in acidic, basic and neutral medium. The stability-indicating potential of the method was assessed by recovery studies in the forced degraded solutions of the drug. The method was validated in accordance with the International Council for Harmonisation guidelines with respect to linearity, accuracy, precision, limit of detection, limit of quantification, and robustness. Excellent linearity was noted within the concentration range 2.0–30.0 µg/mL (0.1 N hydrochloric acid), 0.5–15.0 µg/mL (0.1 N sodium hydroxide), 0.1–20.0 µg/mL (water) with corresponding correlation coefficients of 0.9963, 0.9989, and 0.9998. Limits of detection and quantitation for the proposed methods were found to range from 0.025 to 0.044 and from 0.077 to 0.1357 µg/mL, respectively, for the three methods. The proposed methods were used to quantify the drug in its marketed capsule formulation, with good recoveries suggesting their applicability to routine analysis of the drug in bulk as well as in formulation.

This work was aimed at creating a new, fast, and accurate UV spectrophotometric method for quantifying prazosin hydrochloride in pure and tablet dosage forms. A phosphate buffer solution of pH 6 was used as a diluent. The highest absorbance of prazosin hydrochloride was measured at 247 nm, and the linearity ranged from 2 to 8 µg/mL. The regression equation for prazosin hydrochloride was y= 0.087x + 0.236, with a correlation value 0.987. The percentage of recovery ranged from 99.6 to 101%. The relative standard deviation for intraday precision and interday precision was determined to be less than 2. The LOD and LOQ of prazosin hydrochloride were determined to be 0.0375 and 0.113 µg/mL, respectively. International Council for Harmonisation criteria validated the spectrometric technique and was suitable for routine quantitative measurement of prazosin hydrochloride in pure and tablet dosage forms.

Idelalisib is a phosphatidylinositol 3-kinase delta inhibitor approved by the FDA and the EMA for the treatment of lympholytic lymphoma, B cell non-Hodgkin lymphoma, and lymphocytic lymphoma. The present report describes the validation of a simple, rapid, sensitive, and cost-effective zero-order and first-order derivative spectrophotometric method for the estimation of idelalisib in bulk and in its marketed formulation. Preliminary spectrophotometric analysis of the drug was carried out in methanol and a total of 12 parametric variations were considered. Three selected method variants employing peak-zero and peak-peak techniques were assessed for their stability indicating potential in stress degraded solutions of the drug. The developed method was validated with respect to linearity, accuracy, precision, and robustness. Excellent linearity was observed within the concentration range 1.0–60.0 μg/mL with a correlation coefficient of 0.9997. The limits of assay detection values were found for the range 0.42–3.11 μg/mL, and quantitation limits ranged from 1.29 to 9.42 μg/mL for the proposed method variants. The proposed method was used to quantify the drug in its marketed tablet formulation, and good recoveries ranging from 95.98 to 98.81% were obtained.

The current study is focused on the ultraviolet spectrophotometric technique for the method development and validation of quercetin following the International Conference on Harmonisation guidelines for quantitative analysis. The developed and validated UV method is then applied to the solubility studies of quercetin in various solvents. The stock solution was prepared and further scanned to determine the wavelength at which the solution showed maximum absorbance (λ_max). The λ_max of quercetin was detected at 376 nm. Using various criteria such as precision, linearity, accuracy, the limit of quantification, the limit of detection, and ruggedness, the developed method was further validated. The sample solutions of the drug were made in the concentration having a range of linearity from 2 to 10µg/mL at a selected wavelength of 376 nm. The linear regression analysis data revealed a complementary linear relationship with the value of the correlation coefficient at 0.9997. The recovery experiment, which was carried out at three levels of 80, 100, and 120%, was used to examine the accuracy of the devised method utilizing percentage recovery (96.78–99.18). The precision parameter for validation was carried out by performing intraday and interday variations. Two experts examined the ruggedness. Among all the solvents used, methanol was observed to show the highest solubility of quercetin (111.785± 0.263 μg/mL). The developed method was established to make it modest, safe, definite, sensitive, rapid, suitable, and economical for the quantitative evaluation of quercetin. However, the values observed for limit of detection (LOD) and the limit of quantitation (LOQ) were higher (i.e., 0.1805 and 0.5470, respectively) for the UV method than for the previously reported expensive and sophisticated RP-HPLC method (reported LOD and LOQ were 0.00488 and 0.03906 µg/mL, respectively) and HPLC method (reported LOD and LOQ were 0.05 and 0.1 µg/mL, respectively). However, we were able to develop an accurate, cost-effective, and precise method that can be utilized for routine quality control analysis of quercetin.

A sensitive, easy, and low-cost method used in the determination of pure forms of losartan and mebeverine hydrochloride, also in pharmaceutical preparations with derivative spectrometry using UV–Vis technology. This method depends on measuring the first derivative of the spectrum using zero cross, peak to base line, and peak area. The linear range of concentrations used was equal to 2–14 ppm for losartan, whereas for mebeverine hydrochloride it was equal to 2–16 ppm in a mixture. For losartan, in the presence of mebeverine hydrochloride, 12 ppm by utilizing peak to baseline correlation coefficients 0.9984, 0.9994, and peak area 0.9972, whereas for mebeverine hydrochloride in the presence of losartan, 12 ppm by utilizing peak to fundamental correlation coefficients 0.9952, 0.9966, 0.9957, and peak area 0.9970, 0.9971, 0.9968, 0.9971. The limit of detection for each drug, losartan and mebeverine hydrochloride, is equal to 0.0113 ppm. The accuracy and precision of the method were estimated by calculating relative standard deviation (RSD%) values less than 3% while maintaining a recovery percentage of acceptable value. The proposed method proved effective and efficient at estimating both losartan and mebeverine hydrochloride, in the presence of the other in a mixture of the two without interference, despite the closeness of their spectral absorption peaks. There are no other more accurate methods for estimating the two in a mixture than the proposed method. The proposed method is considered one of the most direct and economical methods that do not require reagents or additional materials for conducting reactions and studying the optimal conditions for those interactions. Thus, it is considered one of the green chemistry techniques that reduce the use of chemicals and reagents in the process of estimating these drugs in a mixture and in a shorter period of time. The proposed method can be used to estimate the different properties in a mixture of the two compounds whose absorption spectra are close.