Absorption Spectra Of Solutions Research Articles

Synthesis and Characteristics of CdS Nanoparticles in Normal (1 g) and Simulated Microgravity (SMG)

In the present investigation, the cadmium sulphide (CdS) nanoparticles are synthesized in the normal gravity i.e. 1 g (called as control) and in simulated microgravity (called as SMG). The SMG was created by using an instrument called Random Positioning Machine (RPM). Cadmium sulfide nanoparticles were synthesized by using standard chemical method under normal gravity (1 g) and simulated microgravity conditions. The synthesized CdS nanoparticles were characterized by Ultraviolet Visible spectroscopy, Fourier Transform Infrared Ray spectroscopy (FTIR), X-ray diffraction (XRD). The UV-visible absorption spectrum of CdS nanoparticle solution showed a distinct absorption peak at 472.19 nm in control and 458.26 nm in SMG. The band gap calculated from the absorption edge for microgravity sample was 2.71 eV and for control sample was 2.63 eV. The crystalline size of CdS nanoparticles synthesised in control and Micro-g was determined by XRD. Obtained results showed smaller the particle size in microgravity sample (10.78 nm) as compared to control sample (13.89 nm).

Simultaneous determination of nitrate, chemical oxygen demand and turbidity in water based on UV-Vis absorption spectrometry combined with interval analysis.

In this paper, a new method for simultaneous determination of nitrate, COD and turbidity in water based on UV-Vis absorption spectrometry combined with interval analysis was studied. By analyzing the spectral absorption characteristics of nitrate, COD, and turbidity standard solutions and the mixtures of them, the absorption spectra in the range of 225-260nm, 260-320nm and 320-700nm were selected as the characteristic spectra of nitrate, COD and turbidity, respectively. Multiplicative scatter correction was employed to compensate turbidity of the absorption spectra of the mixture solutions in the wavelength range of 225-320nm. Then, the spectra after turbidity compensation in the range of 225-260nm was compensated for COD using the method of spectral difference. The original spectra in the range of 320-700nm, the turbidity compensated spectra in the range of 260-320nm, and the COD compensated spectra in the range of 225-260nm were analyzed by PLS algorithm in order to calculate the concentrations of nitrate, COD and turbidity in the mixture solutions. The results showed that this method could simultaneously and accurately determine the concentrations of nitrate, COD and turbidity. After interval analysis, all the correlation coefficients (R2) between the predicted values and the true values of nitrate, COD and turbidity were higher than 0.9, and root mean square error (RMSE) of predicted values were between 0.696 and 2.337.

Perylene diimide based low band gap copolymers: synthesis, characterization and their applications in perovskite solar cells

In this study, newly designed perylene diimide based polymers P1 and P2 were synthesized and were used as hole transporting materials in place of the more common spiro-OMeTAD in perovskite solar cells. The co-polymers P1-P2 were synthesized by Suzuki and direct arylation polymerizations of 2,9-bis(7-bromo-9,9-dioctyl-9H-fluoren-2-yl)anthra[2,1,9-def:6,5,10-d’e’f’]diisoquinoline-1,3,8,10(2H,9H)-tetrone M1 with 5,11-bis(2-hexyldecyl)-3,9-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,11-dihydoindolo[3,2-b]carbazole M2 and 3-octylthiophene M3, respectively. P1 and P2 exhibit broad absorption spectra in thin film and solution with the absorption extending from the ultraviolet to visible and near infrared region of the solar spectrum. The water contact angles of P1-P2 were determined to be 100.8° and 122.9°, respectively, showing good hydrophobicity for the synthesized copolymers. Both polymers show steady state photoluminescence quenching when blended with perovskite. Perovskite solar cell devices fabricated using P1-P2 in place of spiro-OMeTAD show power conversion efficiencies of 13.02% and 10.74%, respectively and manifest the potential of this class of materials as promising alternatives to conventionally used spiro-OMeTAD.

Dataset for reproducing absorption spectra of methyl orange from the RGB values of microscopic images.

The present dataset is related to the research paper entitled “Reproducing Absorption Spectra of pH Indicators from RGB Values of Microscopic Images” (Inagawa et al., 2020). The dataset contains microscopic images of aqueous methyl orange (MO), absorption spectra acquired with a spectrophotometer, loading spectra and calculation sheets for reproducing absorption spectra of aqueous MO from their RGB values of the microscopic images. The microscopic transmission images of the standard MO solutions at various pH conditions were acquired with a CMOS camera equipped with an invert microscope. Meanwhile, the loading spectra were obtained by principle component analysis of a series of absorption spectra of the standard solutions. The conversion matrix from RGB values in a region of interests (ROI) to score values were linear-algebraically determined from the RGB values and score values of the standard solutions. The absorption spectra of the sample solutions of which pH conditions are unknown were then reproduced by calculating the linear combination of the loading spectra with the score values obtained from the conversion process. Herein, the absorption spectra of MO are reproduced at various pH and ROI conditions.

Investigation of Changes in the Absorption Spectrum of Modern Chlorine-Containing Medicines for Photodynamic Therapy and Methylene Blue as a Result of Exposure to LED Emissions with a wavelength of 656 ± 10 nm

Changes in the absorption spectra of aqueous solutions of modern chlorinated photosensitizing drugs for photodynamic therapy “Revixan” (Areal, Russia) and “Chloderm” (Chloderm, Russia) in the range of 600–700 nm depending on the intensity and time of exposure to LED emission with a wavelength of 656 ± 10 nm have been studied. The parameters of the CIE Lab color model of the “Revixan” water solution image before and after LED exposure have been studied. In the range of 400–900 nm, the changes in the absorption spectra of an aqueous solution of methylene blue with different initial concentrations after exposure to LED emission with a wavelength of 656 ± 10 nm and an intensity of 180 ± 20 mW/cm2 have been studied. It has been shown that the effect of LED emission changes the absorption spectra of the studied substances and increases the parameter L (brightness) of the CIE Lab color model for “Revixan”. An increase in the intensity of the LED emission and exposure time causes a decrease in the absorption for “Revixan” and “Chloderm” in the range of 600–700 nm and a shift of the peak of the absorption band lying in this range to the infrared region. The effect of the LED emission on an methylene blue aqueous solution causes a decrease in its absorption in the range of 400–900 nm.

Structure–Property Relationships on the Optical Properties of Rhodamine Thin Films

The spectroscopic properties of five xanthene dyes with varying structures and charges were studied as dilute solutions in ethanol and as thin films on a glass substrate. Density functional theory calculations were used to assign the spectral peaks in the visible region of the solution absorption spectra. These assignments were used as guides to understand the changes of the absorption and emission spectra of thin films as the surface density of the dye was increased. Dilute solutions and submonolayer thin films exhibited similar spectra but with shifts that were accounted for by the difference of polarity of the ethanol solvent compared to the glass/air interface. As the thin films reach monolayer levels, the absorption and emission spectra exhibit features that are assigned to excitons and excimers. The intensities of the emission spectra are most strongly affected by the surface density of the dyes. The maximum emission intensity is found at about 1 monolayer dye coverage, while the total intensity approximately follows a log-normal distribution as a function of dye surface coverage.

Quantification of chlorophyll a, chlorophyll b and pheopigments a in lake sediments through deconvolution of bulk UV–VIS absorption spectra

Assessments of aquatic paleoproduction and pigment preservation require accurate identification and quantification of sedimentary chlorophylls. Using chromatographic techniques to analyze long records at high resolution is impractical because they are expensive and labor intensive. We have developed a new rapid and low-cost approach to infer the concentrations of chlorophyll a, chlorophyll b and related chlorophyll derivatives (pheopigments a) from the mathematical decomposition of UV–VIS measured bulk spectrophotometer absorption spectra of standard solutions and sediment extracts. We validated our method against high-performance liquid chromatography (HPLC) measurements on standard solutions and on varved, anoxic sediment from eutrophic Lake Lugano (Ponte Tresa sub-basin, southern Switzerland), where the history of productivity is relatively well known for the twentieth century. Our mathematical approach quantifies the concentration of chlorophyll b ( $$ {\text{R}}_{{{\text{ad}}_{\text{J}}}}^{2} $$ = 0.99, RMSEP ~ 5.9%), chlorophyll a ( $$ {\text{R}}_{{{\text{ad}}_{\text{J}}}}^{2} $$ = 0.98, RMSEP ~ 5.0%), and pyropheophorbide a ( $$ {\text{R}}_{{{\text{ad}}_{\text{J}}}}^{2} $$ = 0.99, RMSEP ~ 7.8%) in standard solutions. We obtain comparable results for total chloropigment a (chlorophyll a + pheopigments a), chlorophyll a and diagenetic products (pheopigments a) in the sediment samples of our case study (Ponte Tresa). Here, HPLC concentrations of chlorophyll b are very low. The method has, however, the potential to achieve values for chlorophyll b concentrations in sediments with chlorophylls a/chlorophylls b ratios lower than 3.4. The pigment stratigraphy of the Ponte Tresa sediments correspond very well with the paleoproduction and eutrophication history of the twentieth century. The ratio between chlorophyll a and pheopigments a used as a qualitative indicator of sedimentary chlorophyll preservation (chlorophyll a/{chlorophyll a + pheopigments a}) is only weakly correlated with aquatic paleoproduction (radj = 0.35, p-value = 0.045) and remained remarkably constant in the recent century despite strong anthropogenic eutrophication. The new method is useful for obtaining, in a cost- and time-efficient way, information about major sedimentary pigment groups that are relevant to inferring paleoproduction, potentially green algae biomass, pigment preservation and early diagenetic effects.

Development and Validation of Analytical Methods for the Identification in Canprophem - АK® Suppositories with the New Original Polyene Antibiotic

Introduction: The paper presents analytical methods for the identification of Roseofungin active pharmaceutical ingredient (API) using thin layer chromatography (TLC) and spectrophotometry in the ultraviolet region, for the drug CANPROFEM - AK® containing the original polyene antibiotic Roseofungin in the form of suppositories. The study established optimal conditions for the experiment, including sample preparation; the Specificity validation characteristic was examined for each method. Results: Method 1 employed the TLC plate pre-coated with a layer of F254 silica gel using n-butanol saturated with purified water as a mobile phase; the substance was identified in UV light at a wavelength of 365 nm. The method makes it possible to uniquely and specifically identify roseofungin in the presence of placebo components. In method 2, the maximum of the ultraviolet absorption spectrum of the solution being tested coincides with the maximum of theultraviolet absorption spectrum of the reference sample solution (364±2 nm). Conclusion: The methods are suitable for solving the intended objectives and are included in the draft analytical normative document on the finished product quality control by the Identification characteristic.

An Open Access Data Set Highlighting Aggregation of Dyes on Metal Oxides

The adsorption of a dye to a metal oxide surface such as TiO2, NiO and ZnO leads to deprotonation and often undesirable aggregation of dye molecules, which in turn impacts the photophysical properties of the dye. While controlled aggregation is useful for some applications, it can result in lower performance for dye-sensitized solar cells. To understand this phenomenon better, we have conducted an extensive search of the literature and identified over 4000 records of absorption spectra in solution and after adsorption onto metal oxide. The total data set comprises over 3500 unique compounds, with observed absorption maxima in solution and after adsorption on the semiconductor electrode. This data may serve to provide further insight into the structure-property relationships governing dye-aggregation behaviour.

Large Area Free-Standing Single Crystalline Films of p-Quinquephenyl: Growth, Structure and Photoluminescence Properties

Studies of the growth of large-area free-standing single-crystalline films of p-quinquephenyl are presented. High-quality crystals were grown by slow cooling of a hot chlorobenzene solution. Worse quality large-area free-standing single crystals of p-quinquephenyl were also grown by using physical vapor transport and used for comparison. The crystal structure of p-quinquephenyl at 293 K and 85 K was refined by single-crystal X-ray diffraction. The optical absorption and photoluminescence spectra of solutions and crystalline films were obtained and analyzed; a positive solvatochromic effect was detected.

In situ monitoring of silver adsorption on assembled gold nanorods by surface-enhanced Raman scattering

Self-assembly of metal nanocrystals is able to create a gap of sub-nanometer distance for concentrating incoming light by the strong coupling of surface plasmon resonance, known as a ‘hot spot’. Although the plasmonic property of silver is better than other metals in the visible range, the superior Raman enhancement of silver compared to gold is still under debate. To provide direct evidence, in this work, we studied the silver adsorption on assembled gold nanorods (AuNRs) using in situ surface-enhanced Raman scattering (SERS) measurements. The self-assembled AuNR multimers were used as the SERS substrate, where the 4-mercaptophenol (MPh) molecules in our experiment played dual roles as both probe molecules for the Raman scattering and linking molecules for the AuNR assembly in a basic environment. Silver atoms were adsorbed on the surface of gold nanorod assemblies by reduction of Ag+ anions. The stability of the adsorbed silver was guaranteed by the basic environment. We monitored the SERS signal during the silver adsorption with a home-built in situ Raman spectroscope, which was synchronized by recording the UV–vis absorption spectra of the reaction solution to instantly quantify the plasmonic effect of the silver adsorption. Although a minor change was found in the plasmonic resonance wavelength or intensity, the measured SERS signal at specific modes faced a sudden increase by 2.1 folds during the silver adsorption. The finite element method (FEM) simulation confirmed that the silver adsorption corresponding to the plasmonic resonance variation gave little change to the electric field enhancement. We attributed the mode-specific enhancement mechanism of the adsorption of silver to the chemical enhancement from charge transfer (CT) for targeting molecules with a specific orientation. Our findings provided new insights to construct SERS substrates with higher enhancement factor (EF), which hopefully would encourage new applications in the field of surface-enhanced optical spectroscopies.

Biofabrication of silver nanoparticles using leaf extract of Rhynchosia beddomei Baker: spectral characterization and their biological activities

The present study successfully investigated the biofabrication, spectral characterization, and biological activities of silver nanoparticles (AgNPs) using leaf aqueous extract of Rhynchosia beddomei Baker, important crop wild relatives of beans family (Phaseolus). Biofabrication of RB-AgNPs (R. beddomei leaf synthesized AgNPs) was confirmed by color change of the reaction solution from light yellow to dark brown. UV–Vis absorption spectrum of colloidal solution of RB-AgNPs showed characteristic surface plasmon resonance peak at 431 nm. XRD pattern showed that biofabricated RB-AgNPs were crystalline in nature with FCC lattice and the crystallite size was found to be 9.36 nm. TEM micrographs showed that the biofabricated RB-AgNPs were mainly spherical in shape with 20–80 nm in size. DLS analysis revealed that average hydrodynamic radius of RB-AgNPs was 46.5 ± 8.5 nm. Further RB-AgNPs showed very good stability with zeta potential value of − 27.6 mV and polydispersity index of 0.203. FTIR analysis revealed that flavonoids and proteins take part in the bioreduction and stabilization of RB-AgNPs respectively. Biofabricated RB-AgNPs showed effective antioxidant activity against DPPH (IC50 = 69.45 µg/mL) and H2O2 (IC50 = 87.43 µg/mL). RB-AgNPs showed significant antimicrobial activity against both Gram-positive and Gram-negative bacteria. RB-AgNPs were further proved to possess potent cytotoxic activity against different carcinomas including human cell lines of colon carcinoma (COLO205), prostate carcinoma (PC3) and breast cancer (MCF7). Thus RB-AgNPs showed multiple biological functions (3-in-1 system) including antioxidant, antimicrobial and anticancer activities.

N,N-Diarylthiazol-5-amines: Structure-Specific Mechanofluorochromism and White Light Emission in the Solid State

Abstract A range of N,N-diarylthiazol-5-amines having a 4-pyridyl group on a thiazole ring were developed, and their photophysical properties were elucidated. Their synthesis was achieved by applying our methods to the combination of N-arylmethyl secondary thioamides and N,N-diarylthioformamides. This enabled us to obtain amines with different types of aromatic groups on the nitrogen atom. Their absorption and emission spectra in solution were examined. The 4-pyridyl group gives higher polarity to the amines. The solid-state emissions of the amines were also evaluated. Several amines showed mechanofluorochromism (MFC). A 4-pyridyl group on a thiazole ring was a requisite for the expression of MFC properties. Although N-(5-thiazolyl) N,N-di(2-naphthyl)amines did not exhibit MFC by grinding of the pristine powder, white-light emission was observed when the ground powder was fumed with acetone vapor.

Are Alkynyl Spacers in Ancillary Ligands in Heteroleptic Bis(diimine)copper(I) Dyes Beneficial for Dye Performance in Dye-Sensitized Solar Cells?

The syntheses of 4,4′-bis(4-dimethylaminophenyl)-6,6′-dimethyl-2,2′-bipyridine (1), 4,4′-bis(4-dimethylaminophenylethynyl)-6,6′-dimethyl-2,2′-bipyridine (2), 4,4′-bis(4-diphenylaminophenyl)-6,6′-dimethyl-2,2′-bipyridine (3), and 4,4′-bis(4-diphenylaminophenylethynyl)-6,6′-dimethyl-2,2′-bipyridine (4) are reported along with the preparations and characterisations of their homoleptic copper(I) complexes [CuL2][PF6] (L = 1–4). The solution absorption spectra of the complexes exhibit ligand-centred absorptions in addition to absorptions in the visible region assigned to a combination of intra-ligand and metal-to-ligand charge-transfer. Heteroleptic [Cu(5)(Lancillary)]+ dyes in which 5 is the anchoring ligand ((6,6′-dimethyl-[2,2′-bipyridine]-4,4′-diyl)bis(4,1-phenylene))bis(phosphonic acid) and Lancillary = 1–4 have been assembled on fluorine-doped tin oxide (FTO)-TiO2 electrodes in dye-sensitized solar cells (DSCs). Performance parameters and external quantum efficiency (EQE) spectra of the DSCs (four fully-masked cells for each dye) reveal that the best performing dyes are [Cu(5)(1)]+ and [Cu(5)(3)]+. The alkynyl spacers are not beneficial, leading to a decrease in the short-circuit current density (JSC), confirmed by lower values of EQEmax. Addition of a co-absorbent (n-decylphosphonic acid) to [Cu(5)(1)]+ lead to no significant enhancement of performance for DSCs sensitized with [Cu(5)(1)]+. Electrochemical impedance spectroscopy (EIS) has been used to investigate the interfaces in DSCs; the analysis shows that more favourable electron injection into TiO2 is observed for sensitizers without the alkynyl spacer and confirms higher JSC values for [Cu(5)(1)]+.

Understanding the absorption spectrum of mesityl oxide dye in solvents of different polarities

Abstract Understanding the solvent contribution to the UV–Vis absorption spectrum of mesityl oxide (MOx) in different solvents is still challenging because of the interplay between the two possible conformations. The syn:anti relative stability changes according to the solvent polarity. In this work a sequential quantum mechanics/molecular mechanics based on a configuration biased Monte Carlo and the explicit use of solvent molecules is adopted to describe in detail the solvent effects. The contributions of the conformation changes, the polarization effects of the solvent molecules in MOx and the explicit solvation are separated and analyzed. The excitation energies are obtained using time-dependent density functional theory (TDDFT B3LYP/6-311++G(d,p)) calculations on statistically relevant configurations of MOx in acetonitrile, methanol and water solutions. Considering the explicit solvent molecules the calculated solvatochromic shift of −120 cm−1, −1410 cm−1 and −2500 cm−1 are obtained for acetonitrile, methanol and water, respectively. These results are in due agreement with the experimental values. The separated contributions of conformation changes, polarization effects and the explicit solvation add to a consistent description of MOx UV–Vis absorption spectra in solution. The delocalization of the valence orbitals into the solvent region is also considered. The results emphasize the role of the solvent polarity and the limitations of methods that do not include explicit solvent molecules and the thermodynamic condition that characterizes a liquid system.

Remote Modification of Bidentate Phosphane Ligands Controlling the Photonic Properties in Their Complexes: Enhanced Performance of [Cu(RN‐xantphos)(N^N)][PF6] in Light‐Emitting Electrochemical Cells

AbstractA series of copper(I) complexes of the type [Cu(HN‐xantphos)(N^N)][PF6] and [Cu(BnN‐xantphos)(N^N)][PF6], in which N^N = bpy, Mebpy, and Me2bpy, HN‐xantphos = 4,6‐bis(diphenylphosphanyl)‐10H‐phenoxazine and BnN‐xantphos = 10‐benzyl‐4,6‐bis(diphenylphosphanyl)‐10H‐phenoxazine is described. The single crystal structures of [Cu(HN‐xantphos)(Mebpy)][PF6] and [Cu(BnN‐xantphos)(Me2bpy)][PF6] confirm the presence of N^N and P^P chelating ligands with the copper(I) atoms in distorted coordination environments. Solution electrochemical and photophysical properties of the BnN‐xantphos‐containing compounds (for which the highest‐occupied molecular orbital is located on the phenoxazine moiety) are reported. The first oxidation of [Cu(BnN‐xantphos)(N^N)][PF6] occurs on the BnN‐xantphos ligand. Time‐dependent density functional theory (TD‐DFT) calculations have been used to analyze the solution absorption spectra of the [Cu(BnN‐xantphos)(N^N)][PF6] compounds. In the solid‐state, the compounds show photoluminescence in the range 518–555 nm for [Cu(HN‐xantphos)(N^N)][PF6] and 520–575 nm for [Cu(BnN‐xantphos)(N^N)][PF6] with a blue‐shift on going from bpy to Mebpy to Me2bpy. [Cu(BnN‐xantphos)(Me2bpy)][PF6] exhibits a solid‐state photoluminescence quantum yield of 55% with an excited state lifetime of 17.4 µs. Bright light‐emitting electrochemical cells are obtained using this complex, and it is shown that the electroluminescence quantum yield can be enhanced by using less conducting hole injection layers.

Novel Nitrogen-Containing Heterocyclic Non-Fullerene Acceptors for Organic PhotovoltaicCells: Different End-Capping Groups Leading to a Big Difference of Power Conversion Efficiencies.

Novel cores for high performance nonfullerene acceptors (NFAs) remain to be developed. In this work, two new n-type nitrogen-containing organic heterocyclic NFAs, namely, BDTN-BF and BDTN-Th, were designed and synthesized based on a new seven fused-ring core (BDTN) with two different end-capping groups. As a result, BDTN-BF possessed similar absorption spectra in solution and solid state to BDTN-Th, but a slightly higher maximum molar extinction coefficient. Manufacturing the polymer solar cells with PM6 as the donor, the photovoltaic performance of BDTN-BF and BDTN-Th was investigated. The PM6:BDTN-BF-based device achieved the highest power conversion efficiency (PCE) of 11.54% with a high Jsc of 20.20 mA cm-2, a fill factor (FF) of 61.46%, and a large Voc of 0.93 V, and the energy loss (Eloss) was calculated to be 0.48 eV. Comparatively, the PM6:BDTN-Th-based device achieved the maximum PCE value of only 3.53% because of inadequate Jsc and FF. The higher Jsc and FF for the PM6:BDTN-BF-based device was mainly due to the effective electron transfer from PM6 to BDTN-BF, more balanced μh/μe, higher electron mobility of the neat film, better charge collection and dissociation efficiency, and more favorable morphology. These results demonstrate that the acceptors with nearly identical absorption spectra could result in a significant difference in photovoltaic performance, which stress the importance of end-capping units. Furthermore, few NFA-based devices achieve large Voc and high Jsc simultaneously as one based on PM6:BDTN-BF, indicating that nitrogen hybridization of NFAs may be an efficient strategy to realize high and balanced Voc and Jsc.

Validated spectrophotometric methods for simultaneous determination of nebivolol hydrochloride and valsartan in their tablet

Four simple spectrophotometric methods have been developed for the simultaneous determination of nebivolol (NEB) and valsartan (VAL) in bulk and in synthetic mixture simulated to tablet dosage form. Method (I) was area under curve (AUC) which based on the measurement of area between 246 and 256 nm for VAL and 273 and 283 nm for NEB. Method (II) applied the first derivative of ratio spectra (1DD) using VAL 40.0 µg/mL as divisor for determination of NEB, the amplitude of the peak at 294.5 nm was directly proportional to NEB concentration. NEB (30.0 µg/mL) was used as divisor for determination of VAL. The amplitude of peak at 253.4 nm was directly proportional to VAL concentration. Method (III) was the ratio difference (RD) method which based on the measurement of difference in amplitudes (∆P) in the ratio spectra; ∆P (291-275) was directly proportional to NEB concentration, and ∆P (239.2-301.5) was directly proportional to VAL concentration. Calibration curves of the three methods are linear over the concentration ranges of 2.0–80.0 µg/mL and 4.0–80.0 µg/mL for NEB and VAL, respectively. The mean percentage recovery ± SD values for tablet assay for NEB and VAL, respectively were found to be 100.59 ± 1.32 and 100.55 ± 1.12 using AUC, 100.02 ± 1.52 and 101.18 ± 0.42 using 1DD method, and finally 101.38 ± 1.88 and 101.24 ± 0.28 using RD method.Method (IV) involved multivariate spectrophotometric methods including classical least squares (CLS), principal component regression (PCR), and partial least squares (PLS) applied to the UV absorption spectra of the standard solutions containing both drugs recorded in the range of 272–282 nm at 1 nm intervals. Calibration was performed using training set consisting of ten binary mixture solutions in different combinations in range of 5.0–60.0 µg/mL NEB and 15.0–80.0 µg/mL VAL. The mean percentage recovery ± SD values for tablet assay for NEB and VAL, respectively were found to be 100.69 ± 1.54 and 100.90 ± 0.55 using CLS, 100.72 ± 1.54 and 100.89 ± 0.55 using PCR, and 100.72 ± 1.54 and 100.89 ± 0.55 using PLS. The four developed methods were validated and showed successful application to the simultaneous determination of NEB and VAL in their synthetic mixtures. ICH guidelines were used to validate the methods. F and t-tests were used for statistical comparison between the results obtained by the developed methods and those of the reported one. No significant difference was observed regarding both accuracy and precision.

Observation of the complex spectra for the supramolecular system involving silver nanoparticles‐biaryl Schiff bases containing the nitro group

AbstractA series of biaryl Schiff bases containing the nitro groups, 4‐XArCH═NArNO2‐4′ (XBANO2‐4′) and 4‐NO2ArCH═NArY‐4′ (4‐NO2BAY), were synthesized. Also, the fish sperm DNA (fsDNA) and silver nanoparticles (AgNPs) solutions were prepared. By mixing these compounds with fsDNA or AgNPs solution and determining the ultraviolet absorption spectra of the mixture solutions, an interesting phenomenon was found: a new absorption peak λmax,lim appeared in the (XBANO2‐4′)‐AgNPs solution, which was longer than the wavelength of λmax of XBANO2‐4′ solution. The new absorption peak in the (XBANO2‐4′)‐AgNPs solution was the complex spectrum originating from the electron transfer between XBANO2‐4′ and AgNPs. Whereas this phenomenon was not observed in the (4‐NO2BAY)‐AgNPs solutions, a quantitative correlation analysis was carried out with the measured spectral data, and the results show that the wave number νmax,lim of the λmax,lim is mainly affected by the excited‐state substituent constant rather than the ground Hammett constant σ of the X group. The redshift magnitude Δνmax,WSL, namely, Δνmax,WSL = (1/λmax) − (1/λmax,lim), of the wavelength λmax,lim is related to the highest occupied molecular orbital and lowest unoccupied molecular orbital of XBANO2‐4′. The discovery of this new phenomenon is helpful to understanding the interaction between AgNPs‐organic compound supramolecular systems.

Simultaneous estimation of naltrexone and bupropion in pharmaceutical dosage form by using UV spectroscopy

A sensitive and validated method has been developed for simultaneous estimation of Naltrexone and Bupropion in pharmaceutical dosage form by using UV Spectroscopy, without prior separation, by four different techniques (Simultaneous Equation, Absorbance Ratio method, Dual Wavelength Method and Derivative Spectroscopic Method). The work was carried out on Shimadzu electron UV1800 double beam UV-Visible spectrophotometer. The absorption spectra of reference and test solutions were carried out in 1 cm matched quartz cell over the range of 200 - 400 nm. The linearity ranges for Naltrexone and Bupropion were 2-10 μg/ml. The results of the analysis have been validated statistically and by recovery studies. The proposed procedures are rapid, simple, require no preliminary separation steps and can be used for routine analysis of both drugs in quality control laboratories.