Dielectronic recombination of the Cd⁺  (4d¹⁰5s ²S_1/2) ion via formation of the 4d⁹5s² 5p ³D^o₁ Cd atom autoionization state and its radiative decay on the 4d¹⁰5p^{2 3} P_J autoionization states was detected and studied in intersecting electron and ion beams using UV spectroscopy. The 4d⁹5s² 5p ³D^o₁ → 4d¹⁰5p^2 3P₀ radiation transition is found to be the most intensive. The effective cross-section of dielectronic recombination at the maximum equals (5.0+2.0)•10^–17 сm²  which is comparable with those for the electron excitation of the spectral lines (including resonance ones) of the ion under investigation. High probability of radiative decay of the 4d⁹5s² 5p ³D^o₁ autoionization state is due to the interconfigurational interaction (4d¹⁰5s5p + 4d¹⁰5p5d + + 4d⁹5s² 5p + 4d⁹5p³ ).

Lignin preparations were obtained from harsh flax fiber and material exposed to an alkaline solution of borohydride sodium using the Bjerkman extraction method. Peaks of individual vibrational processes of all types of covalent bonds in the functional groups of the biopolymer were identified. The mechanism of induced lignin destruction as a result of destabilization of the ether bond adjacent to the reduced carbonyl group in the propane link of the macromolecule was confirmed. The reduction of carbonyl is accompanied by a twofold increase in the intensity of the absorption band of alkyl hydroxyls and a fourfold increase in the number of hydroxyaryl groups, which indicates to the accumulation of structural units in the free phenolic form in the system. The dynamics of structural transformations was compared, and the duration of the serial-parallel processes of polymer reduction and destruction was estimated.

Dimerization of 5,10,15,20-tetrakis(6-N-methylquinolinyl)-porphyrin in water solutions in the temperature range of 274—343 K was studied using absorption and fluorescence spectroscopy. The equilibrium dimerization constant K_D was shown to vary in a wide range upon the temperature changes. The enthalpy ΔH^≠ and entropy ΔS^≠ of dimerization in solution with different ionic strength were measured and dimerization was found to be enthalpy driven process in all the cases. Large negative values of the dimerization enthalpy ΔH^≠ were proposed to be explained by the optimal overlapping of porphyrin macrocycles due to the minimization of the Coulomb repulsion of ionized peripheral substituents located at a large distance from the macrocycle.

The spectral-luminescent properties of new complexes of chloro-lutetium(III) with 5,10,15,20-tetra- phenylporphin and its mono-nitrophenyl derivative having a para-nitro group in one of the meso-phenyl rings were studied. The studied complexes show weak fluorescence (φ_fl = 5 ⋅ 10^–4) and moderate phospho- rescence (φ_phosph = 3 ⋅ 10^–2) and also phosphorescence at room temperature at 77 K. The type of an extra ligand (monodentate — chlorine and bidentate — acetylacetonate) as well as the presence of electron- withdrawing NO₂ group in the meso-phenyl ring have no appreciable effect on photophysics of Lu(III) por- phyrins. The phosphorescence spectrum of the studied complexes is shifted to the long-wavelength region, and the phosphorescence lifetimes are longer (2800–3100 µs) than those of the known oxygen sensors — Pt(II)- or Pd(II)-porphyrins. The value of the oxygen determination limit in solutions was estimated from the quenching of the phosphorescence of the studied Lu(III) porphyrins.

A detailed interpretation of exciton lines caused by the presence of a lithium impurity in ZnO crystals (T = 4.2 K) was carried out: the 368.5 nm line is caused by the radiative recombination of excitons bound on neutral donor states Li_i^x; the 371.2 nm line is caused by the same process, but occurring simultaneously with the transition of the donor to the excited state; the 368.2 nm line occurs when excitons bound on ionized Li_i⁺ states emit, and finally, line 369.7 nm is the emission of excitons bound on acceptor complexes of the form (Zn_i ⁺ Li_Zn^| ), (In_Zn⁺ Li_Zn^| ), (Li_i ⁺ Li_Zn^| ), etc. The measurement data also made it possible to calculate the ionization energy of shallow donors Li_i^x:E_d = 0.033 eV. Thus, a method for exciton spectroscopy of lithium states affecting the optical and electrophysical characteristics of zinc oxide has been developed.

Laser-induced breakdown spectroscopy (LIBS) is considered as a method for elemental analysis of concrete in situ. However, the content of chlorine responsible for corrosion of iron reinforcement may be lower than the LIBS sensitivity needed to detect corrosion at the initial stage. This is especially true for the portable LIBS systems without gating and signal amplification. To detect corrosion, it is proposed to use analytical signals of elements-products of reinforcement corrosion (Fe, Mn, Cr) when they emerge on the concrete surface. It was found that the signals of iron, manganese, and especially chromium can be reliably registered using LIBZ-200 only on the surface areas painted with corrosion products.

Simulation of the coherent excitation of molecules by laser radiation is carried out. It is based on simple models, i. e., quantum systems with N+1 energy level. The exact solution of differential equations describing the process in terms of the simplest semi-classical Rabi model is obtained without integration of differential equations but discrete mathematics with Fourier transform and discrete orthogonal polynomials is used. The Fourier transform realizes the transition from continuum t-space with time-dependent probability amplitudes a_n(t) of a quantum system to discrete Fourier space where Fourier spectra F_n(ω) are spectral images of a_n(t). The spectra are shown to be described by some discrete orthogonal polynomial sequence corresponding to the quantum system. The example shows how using specially constructed polynomials one can calculate the Fourier spectra and find the probability amplitudes a_n(t) describing the excitation of a quantum system. The established one-to-one correspondence between the polynomial characteristics and the coefficients of differential equations allows us to calculate all the characteristics of quantum systems whose excitation is described by the solution. Thus, the transition from functions a_n(t) to their spectral space allows one to solve some dynamical equations without integration reducing the problem to calculating the finite sum from 0 to N.

The use of X-ray spectroscopy is considered in studying the specific distribution of alloying elements in the structural components of heat-resistant nickel alloys, namely between secondary carbides, since the role of carbides in the formation of the properties of these alloys is complex. The theoretical modeling of thermodynamic processes of separation of excess phases using the CALPHAD method in the JMatPro software shell is carried out. Also, the structure and distribution of chemical elements in carbides depending on the alloy alloying are studied using a scanning electron microscope REM-106I. It is established that in typical M₂₃C₆ and M₆C carbides for the ZhS6K alloy, there is a tendency to degenerate phase reactions depending on the level of doping by the given elements. The mathematical dependences of the influence of the alloy alloying on the temperature of carbide separation (dissolution) and changes in the chemical composition of the alloy on the content of elements in the carbides are established. When the content of chromium is increased, the M₆C carbide gradually degenerates and disappears at 11 mas.%. When the molybdenum content in the alloy is 3 mas.%, a topologically tightly packed TSH phase in the structure is formed, while at 8 mas.% Mo, M₆C carbide approaches the molybdenum-based monocarbide. The dependences of the temperatures of separation (dissolution) of the carbides on the amount of tungsten content in the alloy are calculated. An increase of tungsten in the alloy was found to increase the temperature of releasing (dissolution) of all carbides in the alloy. At a concentration of 11 mas.% in the tungsten alloy, the TSH phase is released, which negatively affects the properties of the system under study. The obtained dependences were experimentally confirmed using X-ray spectroscopy on the heat-resistant nickel-based alloys ZhS6K. The stoichiometric formulas of the carbides were calculated, the theoretical and practical results were compared and their agreement was established.

Mn_0.3Ag_0.7In_4.1S_6.8 single crystals were grown by directed melt crystallization, their composition and crystal structure were determined. It was established that the single crystals Mn_0.3Ag_0.7In_4.1S_6.8 crystallize in a cubic spinel structure. The band gap of the single crystals was estimated from the transmission spectra in the region of the fundamental absorption edge in the temperature range of 20–320 K, and its temperature dependence was constructed. It was shown that the temperature dependence of the band gap has the form characteristic for semiconductor materials.

Samples of a series of Cu_1–xPd_xFeS₂ (x = 0—0.02) compounds were studied by ^63,65Cu NMR in a local field at a temperature of 77 K. The spectra of the samples were measured, their parameters were determined, and the fields in the region of ^63,65Cu nuclei were estimated. An asymmetric broadening of the resonance NMR lines with a smoother decay in the high-frequency region was found, which may be the result of an increase in the number of defects in the crystal lattice of the compound. Such defects can be Fe_Cu²⁺  antisite defects, the formation of which is caused by the formation of the PdS phase in the chalcopyrite matrix with an increase in the nominal Pd content.

The dynamics of transient absorption spectra of H*- and J-aggregates of an intoricarbocyanine dye was studied using femtosecond pump-probe spectroscopy. Transient bleaching decay of the H*-aggregates proceeds with two time constants of ~3 ps and ~30 ps upon excitation at 400 nm and with a single time constant of ~30 ps upon excitation at 800 nm. Transient bleaching decay of the J-aggregates contains two components with time constants of ~1 ps and ~20 ps, respectively, upon excitation at both 400 nm and 800 nm. The fast component in the transient bleaching decay of the H*-aggregates upon excitation at 400 nm correlates with a direct transition from the top of the exciton band to the ground state. The slow component is due to a competing relaxation from the top to the bottom of the exciton band followed by a transition to the ground state. The fast component in the transient bleaching decay of the J-aggregates corresponds to a direct transition from the nonthermalized excitonic state to the ground state. The slow component is related to the transition to the ground state after intraband exciton relaxation is complete. The longer delocalization length of excitons in the J-aggregates (9 molecules) compared to the H*-aggregates (4 molecules) is manifested in the narrowing of the ground-state absorption band and in the faster decay of the excited states. The H*-aggregates possess a narrow ground-state absorption band at 514 nm, and a weak absorption peaked at 756 nm. Upon excitation at 800 nm the transient bleaching peaks undergo a bathochromic shift as a result of inhomogeneous broadening.

Nanostructured thin films on a silicon substrate were obtained using a high-frequency pulse-periodic f ~ 10—15 kHz laser action at a wavelength λ = 1.064 µm, a power density q = 85 MW/cm² , and a pressure in a vacuum chamber p = 2⋅10^–2 mm Hg on zinc oxide ceramics doped with scandium oxide. The morphology of the obtained films was studied using atomic force microscopy. The features of transmission spectra in the visible, near and middle infrared regions were revealed. The luminescence spectra obtained upon excitation by different wavelengths were practically unchanged. The electrophysical properties of the ZnO +0.9% Sc₂O₃/Si heterostructure were analyzed. It is established that the main conduction mechanism is the current limited by the space charge in the oxide film with deep traps.

It is shown that the ratio of concentrations of near-cluster and conventional radiation color centers increases in magnesium fluoride nanocrystals in the case when the manufactured samples before irradiation are kept for some time at a temperature higher than the anion vacancies mobility temperature. Such preirradiation heat exposure on lithium fluoride nanocrystals leads to the formation of near-cluster aggregation color centers during radiation exposure of the samples. It is established that differences in pre-irradiation thermal effects on the samples affect the kinetic of concentration growth of aggregate near-cluster centers in the post-radiation period. Conclusions are made about the mechanism and processes of nanoclusters formation in the samples, as well as about the defects involved in the formation.

The method for monitoring cell population movement in microscopic video-sequences based on integral optical flow and motion maps is proposed. Through adjustment and calibration of the optical system and averaging consecutive frames, high-quality subsequent images are obtained. Short-term dynamic characteristics are determined by optical flow. Based on optical flow, integral optical flow is calculated and used to create motion maps, and these maps are used to analyze and describe motions in any region of interest. Therefore, different types of cell movements, including directional motion, aggregation and dispersion can be identified. Our method doesn’t require training, it can be used for situation monitoring and analysis, or as a component of comprehensive systems. Experiments performed on synthesized and real microscopic video images show the effectiveness of our method.

We investigate the spectral-luminescent characteristics of eosin, erythrosin, and rose bengal molecules in reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate of sodium. It has been established that the incorporation of dye molecules into reverse micelles causes an increase in their hydrodynamic radii R_h. Meanwhile, a linear dependence of this increase ΔR_h on the degree of hydration w is observed. Magnification of R_h causes a shift in the absorption and fluorescence spectra as well as an additional Stokes shift. It is shown that with increasing R_h, the ratio of the dipole moments of the excited and ground states μ_e/μ_g also increases.

We consider the possibilities of applying the plasmon-enhanced fluorescence of monoclonal antibodies labeled with fluorescein isothiocyanate (FITC) to the prostate-specific antigen (PSA) for increasing the immunofluorescence analysis sensitivity. For the first time, for determining the PSA concentration we applied an immunochemical test system of two-center binding using a pair of non-competing monoclonal antibodies in combination with silver plasmon nanoparticles. The advantages over the standard PSA immunofluorescence assay are shown, namely: the intensity of the recorded fluorescent signal is increased by 2.3—3.2 times in the presence of silver nanoparticles in comparison with the signal of the test system on the intact surface of a polystyrene plate; the signal-to-noise ratio is increased by up to 2 times. In addition to the plasmon-enhanced fluorescence, the effect of an intermediate polyelectrolyte layer on the increasing of the sorption capacity of primary PSA antibodies is shown, which in turn influences the fluorescence signal intensity. A growth of the plasmon fluorescence enhancement factor with increasing the concentration of the labeled antibodies indicates the suppression of the self-quenching of the fluorescent labels by metal nanoparticles.

We studied the physiological and biochemical parameters as well as the elemental composition of Hypogymnia physodes samples from various phytocenoses differing in lighting conditions and air humidity. Under the conditions of severe shading in the spruce forest we observed in H. physodes thalli a significant increase in the content of chlorophyll a and nitrogen, the maximum value of the pheophytinization coefficient, and the minimum content of phenolic compounds. High insolation in birch and pine forests led to a decrease in the values of all the studied biochemical parameters, with the exception for phenolic compounds, the content of which was the highest under these conditions. AES-ICP analysis of H. physodes thalli revealed 20 elements (Al, B, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Pb, Sn, Sr, Ti, V, W, Zn). These elements were found in lichen samples from all the studied natural phytocenoses, with the exception of Mo, which was absent in the samples from black alder forest. The maximum concentration for almost half of the elements (Al, B, Fe, K, Mo, Na, Sn, Ti, V) were determined in the samples from the spruce forest, where, due to the high and more stable level of humidity, the thalli are oftener and longer presented in a hydrated state. Based on the analysis of the cross-correlation of the physiological and biochemical parameters and the metal concentration in the samples, a complex system of correlation relationships was established. The results indicate a high coordination of various physiological processes. A crucial role in the supporting of their consistency under the changing environmental conditions was found for chlorophyll a. The content of this pigment was associated with a more significant number of different physiological and biochemical parameters and element concentrations.

We compared ground-based (Bruker 125 HR) and satellite (OCO-2) datasets of simultaneous CO₂ measurements in the vicinity of St. Petersburg. It is shown that correcting the ground-based XCO₂ values by 2.5% and choosing an optimal setup during the spectra analysis allowed us to reach good agreement between the satellite and ground-based measurements. The bias between the two datasets is –0.01—0.16 ppm (–0.00—0.04%) for the means, and the standard deviation of the means is 1.42—1.49 ppm (0.35—0.37%) with a spatial mismatch of XCO₂ data pairs of 100—300 km. Such small disagreement between the two types of measurements permits to use both methods for solving the inverse task of atmospheric transfer — the estimation of anthropogenic emissions of CO₂.

A novel dipodal fluorescent sensor, N¹ ,N³ -bis(2-(2,3,4-trihydroxybenzylidene)amino)ethylmalonamide (MEP), suitable for the practical measurement of sodium concentration has been successfully developed and characterized by several spectroscopic techniques. The design of the dipodal scaffold includes a central unit, spacer, and fluorophore moiety as structural key features. The fluorescence sensor MEP adopts a photoinduced electron transfer mechanism and shows excellent selectivity for Na(I) among other biologically and environmentally important metal ions, viz., Na(I), K(I), Al(III), Cr(III), Fe(III), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) in DMSO by demonstrating a remarkable enhancement in the fluorescence intensity from 345.5 to 705.5 a.u. at λ_max = 532.9 nm. The 1:2 binding stoichiometry between the ligand and Na(I) ion was confirmed by Stern–Volmer and Hill Plot. The association constant determined for the ligand with the sodium metal ion is found to be very high, 7.7×10⁶ M^–2 , which may be attributed to the trapping of sodium ions into the pseudo cavities of the ligand created by interaction of the ligand and sodium ions. The studies explore potential applications of the ligand for Na(I) ions detection in environmental and industrial applications.

A colorimetric and fluorescent chemical sensor N1 based on o-tolidine was designed and synthesized, which can be used as an efficient colorimetric and fluorescent sensor for CN⁻ . Compared to other common anions, the color of N1 solution was observed from yellow to colorless after the addition of CN⁻, while under UV lamp the yellow fluorescence of N1 was clearly annihilated. In addition, the detection limit on fluorescence response of N1 for CN⁻  was down to 4.43 ⋅ 10^-7 M. ¹H NMR titration suggested that the ICT process occurred between N1 and CN⁻ , and the reaction ratio was 1:2. N1 was successfully used to detect cyanide content in bitter almonds, and N1-based test strips were also produced, which could more conveniently and effectively detect the CN⁻  in aqueous solution.

The neutron energy spectrum is one of the most important characteristic parameters. A novel optical measurement method is proposed. The purpose of the method is to determine the neutron spectra according to the recoil proton track length. The recoil protons deposit energy along the track and excite scintillator luminescence. The luminescence image directly reflects the neutron energy spectra. The Geant4 simulation toolkit is used to study the characteristics of the recoil proton luminescence distribution and determine the detector system response. A reconstruction algorithm based on the potential reduction interior point is developed and applied to spectrum unfolding. This method has the advantages of an intuitive measurement, good energy resolution, suitability for various charged particle beams, a wide energy range, convenience, and an adjustable range.

The analysis of geological samples using laser-induced breakdown spectroscopy (LIBS) is strongly affected by matrix effects. To investigate the improvement of matrix effects by the graphite doping method, rock powder was mixed with graphite powder and pressed into pellets. Four groups of samples with the same graphite content were prepared from a mixture of seven different rock powders and four graphite powders (0, 25, 50, and 75 wt.%). To reduce some of the pulse-to-pulse fluctuations, the internal standardization method was adopted. Four sets of calibration curves of Ca and Mg were prepared using pellet samples with the same graphite content. The influence of graphite content on laser-induced plasma temperature and electron density was further investigated. The coefficients of determination (R²) of the calibration curves after doping graphite are larger than those without doping, and the stability of the spectral intensity, plasma temperature, and electron density after doping are also improved. In particular, when the doping percentage is 50%, the matrix effect is significantly improved. The results show that the graphite doping method has great potential for improving the matrix effects of LIBS in the analysis of rock powder samples.

We present a multiple water-soluble azo dye with a D-π-A-π-D conjugated structure, 3,5-bis-(2,4,6- trihydroxyphenylazo)benzoic acid (THPBA) developed using phloroglucinol as the electron-donating group, benzoic acid as the electron-accepting one, and the azo double bond as the bridging one. The UV-Vis spectral properties of the elaborated structure as well as its spectral response to the pH are investigated in detail. The results show that the present THPBA, combining carboxyl, azo, and multi-hydroxyl groups, possesses excellent UV-vis spectra (ε_max = 2.794×10⁴ –2.115×10⁴  L/mol·cm) with changing pH values and solvents. Especially in DMF-H2O (v/v=1:9), there is an obvious spectral response for THPBA to pH in the linear range 5.2–7.5, which is successfully applied to detect pH values in aqueous and commercial fruit juice samples.

We build a novel fluorescence resonance energy transfer (FRET) method based on N-doped graphene quantum dots (NGQDs)-MnO₂ nanocomposite for rapid, sensitive detection of glutathione (GSH) levels in human serum. In this strategy, MnO2 nanosheets on the NGQDs surface serve as a quencher. NGQDs fluorescence can make a recovery by the addition of GSH, which can reduce MnO₂ to Mn²⁺, and thus the GSH can be monitored. The MnO₂ platform affords minimal background and high sensitivity for detecting GSH in this proposed scheme. Meanwhile, relevant fluorescence on-off-on processes were monitored, and the sensing mechanism was explored.

We employ a novel circular dichroism (CD) technology coupled with statistical analysis to assess the higher order structure (HOS) similarity of commercially available trastuzumab and a proposed biosimilar. This technology shows good potential for enabling the comparison of similarities and differences in secondary and tertiary structure of proteins. Multiple CD spectra in far- and near-UV are obtained reproducibly from a CD spectrometer with fully integrated autosampler and flow cell to eliminate the errors typically associated with sample handling on manual CD spectrometers. The significance of similarities or differences was quantified statistically using three analytical methods (weighted spectral difference, correlation coefficient and area of overlap). HOS comparison of the secondary structure (far-UV CD spectra) suggested similarity between the innovator drug, trastuzumab (Herceptin®), and biosimilar products. However, the tertiary structure (near-UV CD spectra) suggested statistically significant differences. These differences may be due to changes in tertiary structure or to modifications and degradations during the process of production or storage. The results show that the automated circular dichroism technology coupled with statistical analysis is a robust tool for enabling the comparison of similarities and differences in secondary and tertiary structure of protein products.

It is well known that the relaxation rates (1/T₁ and 1/T₂) in H₂O/D₂O mixtures are smaller than those in H₂O alone. The results of this have not been examined in the presence of a low rate of cysts or abscess contents in D₂O. One purpose of this study was to determine the shortening of the relaxation rate distribution interval (SRDI) for D₂O containing cysts or abscess contents. Another goal is to investigate the differentiation of cysts from abscesses with T₁ and T₂ measurements. The ultimate objective is the possibility of a new MRI contrast mechanism for dental lesions. Nineteen odontogenic jaw cysts and 12 jaw abscesses were collected from patients. A mixture was prepared by adding 0.06 mL cyst or abscess content to 0.94 mL D₂O. The experiments were carried out with a nuclear magnetic resonance spectrometer operating at 400 MHz. The mean 1/T₂ of the abscesses was significantly different from that of the cysts (P < 0.005), but the mean 1/T₁ of the non-haemorrhagic cysts was not different from that of the abscesses (P = 0.626). The interval shortening ratios (SRDIs) of 1/T₁ and 1/T₂ for the cystic mixture were 16.36 and 4.22, respectively. The ratios were 8.39 and 2.68, respectively, for the mixture containing abscess contents. In conclusion, the relaxation rate reduction of the mixture results in a shortening of the distribution intervals, which leads to the separation of cysts from abscesses. In addition, the high interval shortening ratios indicate that the results of this study can provide a basis for studies on a new MR contrast mechanism for jaw lesions.

A simple, rapid, and sensitive LC-MS/MS method for assay of Zolpidem in human plasma has been developed and validated using Zolpidem D6 as internal standard (IS). The extraction of analyte and IS was done using 100 µL of plasma sample by solid phase extraction with Strata X™ 33 µm polymeric sorbent cartridges. The processed plasma samples were separated using mixture of methanol and 5 mM ammonium acetate buffer in 0.1% formic acid (80:20, v/v) as mobile phase on a C₁₈ column at a flow rate of 0.7 mL/min with total run time of 2.0 min. The quantification of the separated components was done in positive ion mode by Multiple Reaction Monitoring (MRM) with mass transitions from m/z 308.0 (parent ion) to m/z 235.0 (product ion) for Zolpidem and from m/z 314.2 (parent ion) to m/z 235.0 (product ion) for the IS. The method was linear in the concentration range of 2.0–200 ng/mL. The recovery was 82.49% and 84.24% for Zolpidem and IS. The inter- and intra- day accuracy and precision were in the range of 94.44 to 103.80% and 2.06 to 8.95%, respectively. The proposed method was successfully applied for pharmacokinetic study of Zolpidem in human volunteers after single oral dose of 10 mg under fasting conditions and incurred sample reanalysis was also performed.

Berberine hydrochloride (BH) is a frequently detected antibiotic in environmental waters. The objective of this study was to investigate the photodegradation of the problematic antibiotic in pure water under simulated sunlight (290–800 nm) using a photodegradation chamber. The effects of irradiation time, pH, and the presence of the matrix (nitrate, humic acid, copper, and hydrogen peroxide) were investigated in this study. The results showed that the BH degradation follows pseudo-first-order kinetics, with the degradation of BH decreasing slightly with increasing irradiation time. The rate of BH photolysis was more efficient in the near-neutral condition than in alkaline or acidic solutions and increased in the presence of nitrate and copper. Hydrogen peroxide and humic acid accelerated or inhibited degradation of BH depending on their concentration. The rapid photodegradation of BH under simulated sunlight suggested that photolytic disinfection could also be effective for degradation of the target antibiotics in water.

A novel, simple, sensitive, and selective kinetic spectrophotometric method has been developed for the determination of lorazepam in pharmaceutical and bioloical samples. The procedure is based on the catalytic effect of lorazepam on the Janus Green-bromate reaction system. The change in absorbance was followed spectrophotometrically at 618 nm. To obtain the maximum sensitivity, the reagents concentration, temperature, and time were optimized by one at the time method. Under optimum experimental conditions, the calibration curve was linear over the range 0.3–19.5 μg/mL of lorazepam, including two linear segments. The relative standard deviations (n = 5) for 1.0, 5.0, and 15.0 μmol/L of lorazepam were 1.09, 1.03, and 0.97%, respectively. The limit of detection was 0.08 μg/mL of lorazepam. An experimental check under these optimal conditions confirmed good agreement in the RSM results. The developed method was successfully applied for the determination of lorazepam in real samples, and the obtained results are in a good agreement with those using HPLC.

Five simple, selective, and rapid spectrophotometric methods are developed for the determination of flibanserin (FL) in the presence of its oxidative degradation products (ODPs). Stress studies are performed according to the International Conference on Harmonization (ICH) guidelines to assess the behavior of FL against oxidative, thermal, and acidic conditions. FL was stable against thermal and acidic conditions, while it was susceptible to oxidative degradation. Three of the spectrophotometric methods were univariate methods, namely, third derivative (D³), ratio difference of ratio spectra (RD), and first derivative ratio of spectra (D¹R), while the other two methods were multivariate methods, namely, partial least square (PLS) and principal components regression (PCR). No preliminary separation steps were required in these methods. The chemical structures of the ODPs were confirmed using mass spectrometry and ¹H NMR spectroscopy. The proposed methods were developed and validated according to the ICH guidelines. The linearity, accuracy, and precision were determined, and the selectivity was assessed by analyzing synthetic laboratory mixtures containing different ratios of FL and its ODPs. Statistical comparisons were applied to the five spectrophotometric methods, and no significant differences were found. The validated methods could be applied for routine testing and quality control.

A sensitive element was prepared by the spin coating method on the surface of a K⁺  exchange glass optical waveguide by dissolving tetrakis-carboxyphenyl porphyrin (TCPP) in the nontoxic solvent ethanol. The TCPP sensitive element detected 18 volatile organic compounds with an excellent selective response to ethylenediamine (EDA) gas. On this basis, the effects of the solvent, solution mass fraction, speed of the homogenizer and atmospheric humidity on the detection of EDA gas by the sensitive element were discussed. The formation of hydrogen bonds between TCPP and EDA molecules is proposed, which leads to changes in the morphology and light absorbance of the sensing film.