Spectrophotometric Measurements Research Articles

Fabrication of epoxy composite coating with superior anticorrosive properties using a pH-responsive system based on 2D Zn-MOF nanosheets

Herein, two-dimensional Zn(Bim)(OAc) nanosheets (ZNS) were prepared using ultrasonication and surfactant-assisted methods. Subsequently, it was used as nanocontainer loaded with benzotriazole (BTA) corrosion inhibitor to fabricate BTA@ZNS nanocomposites with pH-controlled release characteristics. The morphology analysis exhibits that BTA@ZNS has a distinct lamellar structure. UV spectrophotometer measurements indicated the release rate of BTA reached 94.38 % in 24 h at pH=1. Adding BTA@ZNS as fillers into epoxy resin (EP) coating can form BTA@ZNS/EP composite coating with active anti-corrosion properties. Electrochemical impedance spectroscopy (EIS) demonstrates that BTA@ZNS/EP coating has superior corrosion resistance than other EP-based coatings. The enhanced anti-corrosion performance is ascribed to the barrier effect and acid-responsive controlled release of BTA@ZNS.

Substitution of additives in horseradish sauce: technological strategies and efficacy

An additive-free horseradish sauce was produced by replacing citric acid and sulfites, commonly used as acidifying, and antimicrobial/anti-browning agents, respectively. Unripe grape juice was used as acidifier, while steam blanching was applied to inactivate horseradish peroxidase (HRP) to avoid browning. Unexpectedly, the heat treatment inactivated myrosinase, responsible for the release of the irritating allyl isothiocyanate from sinigrin's hydrolysis, causing undesired loss of pungency. To restore it, mustard seed powder was added as an ingredient naturally rich in myrosinase. The inactivation of HRP and restoration of myrosinase were evaluated through spectrophotometric measurements of HRP and chromatographic analysis of glucose, a reaction product of myrosinase. The experimental sauce, obtained by adding basic ingredients to horseradish, was stabilized through pasteurization and subjected to sensory analysis and colorimetric evaluation. An additive-free and sustainable horseradish sauce was obtained, using mustard seeds and exploiting thinned bunches as by-products instead of wasting them.

The effect of seed layer cycles on the structural, optical, and morphological properties of ZnO nanorods.

In this study, ZnO seed layers with different cycles were formed on glass substrates by the sol-gel technique, and ZnO nanorods were grown on them by the hydrothermal method. Morphology and the structural characterization of the seed films and the ZnO nanorods are carried out by field emission scanning electron microscopy (FE-SEM) and x-ray diffraction techniques. In addition, to investigate the effect of seed layer deposition cycles on the optical properties of the ZnO nanorod arrays, UV/visible spectrophotometer and photoluminescence (PL) measurements were performed. The changes in structural and optical parameters such as dislocation density, strain, crystallite size, and optical band gap values on each seed layer deposition cycle were examined. The highest optical band gap and crystallite size were obtained for ZnO nanorods with 4 cycles seed layer as 3.22 eV and 63.6 nm, respectively. Also, in the PL spectrum, the largest ratio of UV-emission region to weak-visible emission region was obtained in ZnO nanorods having 4 cycles. In addition, the glucose detection properties of ZnO nanorods having 4 cycles were investigated using the PL measurements and it was found that UV-emission peak intensity of ZnO nanorods decreased as the glucose concentration increased from 8 to 40 mM. The results show that the number of deposition cycles of the seed layer has a strong influence on the orientation, crystal quality, and optical band gap of the growing ZnO nanorods, as well as significantly affecting their morphological properties. RESEARCH HIGHLIGHTS: High quality ZnO nanorods were grown on glass substrates by hydrothermal method. The effect of ZnO seed layer cycles on the structural, optical, and morphological characteristics of ZnO nanorods grown on were examined. It was found that the number of cycles of the seed layer is a critical parameter for growing quality and well-aligned ZnO nanorods.

Characterization of MoS2:Nb sputtered thin films. An application as hole transport layer in Cu2ZnSnS4/Si tandem solar cells

MoS2:Nb films deposited by radio-frequency magnetron sputtering are investigated in view of their application in infrared (IR)-transparent contacts for tandem photovoltaic devices.This material is already known to give a good electrical contact with p-type chalcogenide semiconductors, which are typically grown onto opaque molybdenum metallic contacts and a MoS2 layer spontaneously forms at the back interface during the on-top semiconductor growth. Our study explores a different approach, which involves the direct growth of IR-transparent MoS2:Nb films via sputtering inside complete photovoltaic devices, like Cu2ZnSnS4 (CZTS)-based single junction solar cells and CZTS/Si tandem devices. Films deposited at different sputtering pressures are compared by analysing their microstructure, morphology, chemical composition, optical and electrical properties. The effects of post-deposition sulfurization treatments are also investigated. We find that MoS2:Nb films deposited at around 0.1 Pa exhibit compactness but show a notable sulfur deficit ([S]/[Mo]≈1.4), a significant sub-bandgap optical absorptance and lack of crystallinity. Increasing the Ar pressure to 1 Pa raises the [S]/[Mo] ratio to 2.2, yielding crystalline films with good IR-transparency, although with a porous morphology. Despite 0.5 wt% Nb-doping of the sputtering target, the as-deposited films demonstrate n-type conductivity likely due to uncontrolled impurities and intrinsic defects. Ultraviolet Photoemission Spectroscopy measurements suggest that films’ work function higher than 5 eV can be obtained with a post-deposition sulfurization, making these materials suitable as Hole Transport Layer in photovoltaic applications. A similar increase in work function is expected in the CZTS/MoS2 junctions, since the sputtered MoS2:Nb films undergo a sulfurization process needed to obtain the overlying polycrystalline CZTS absorber.CZTS solar cells produced with sputtered MoS2 and Transparent Conductive Oxides contacts on glass substrates, despite plagued by severe adhesion problems, show the potentiality to give efficiencies comparable to reference devices with standard Mo back contact. Fabrication of CZTS/Si tandem devices on textured silicon bottom cells yields a maximum efficiency of 4.4 %, primarily hindered by the low quality of the CZTS film on textured substrates. Nonetheless, optoelectronic characterizations based on both spectrophotometric and quantum efficiency measurements confirm a good IR transparency of the MoS2-based intermediate contacts and the desired electrical behaviour.

Comparative analysis of cyto-genotoxicity of zinc using the comet assay and chromosomal abnormality test.

In this study, the toxicity of the trace element zinc (Zn) in Allium cepa L. test material was examined. Toxicity was investigated in terms of physiological, cytogenetic, biochemical, and anatomical aspects. Germination percentage, root length, weight gain, mitotic index (MI), micronucleus (MN) frequency, chromosomal abnormalities (CAs), malondialdehyde (MDA), proline and chlorophyll levels, superoxide dismutase (SOD) and catalase (CAT) enzyme activities, and meristematic cell damage were used as indicators of toxicity. Additionally, the comet test was used to measure the degree of DNA damage. Four groups of A. cepa bulbs-one for control and three for applications-were created. While the bulbs in the treatment groups were germinated with Zn at concentrations of 35, 70, and 140mg/L, the bulbs in the control group were germinated with tap water. Germination was carried out at room temperature for 72h and 144h. When the allotted time was over, the root tips and leaf samples were collected and prepared for spectrophotometric measurements and macroscopic-microscopic examinations. Consequently, Zn treatment led to significant reductions in physiological indicators such as weight gain, root length, and germination percentage. Zn exposure caused genotoxicity by decreasing the MI ratios and increasing the frequency of MN and CAs (p < 0.05). Zn promoted various types of CAs in root tip cells. The most observed of CAs was the sticky chromosome. Depending on the dose, Zn was found to cause an increase in tail lengths in comet analyses, which led to DNA damage. Exposure to Zn led to a significant decrease in chlorophyll levels and an increase in MDA and proline levels. It also promoted significant increases in SOD and CAT enzyme activities up to 70mg/L dose and statistically significant decreases at 140mg/L dose. Additionally, Zn exposure caused different types of anatomical damage. The most severe ones are epidermis and cortex cell damage. Besides, it was found that the Zn dose directly relates to all of the increases and decreases in physiological, cytogenetic, biochemical, and anatomical parameters that were seen as a result of Zn exposure. As a result, it has been determined that the Zn element, which is absolutely necessary in trace amounts for the continuation of the metabolic activities of the organisms, can cause toxicity if it reaches excessive levels.

Methanol extract of black garlic protects against hyperuricemia by xanthine oxidase inhibitory activity in-vitro

Garlic (Allium sativum L.) has been used as a medicative food for a long time. However, some individuals are averse to raw garlic owing to its pungent taste and aroma. As a result, a variety of garlic formulations have been created to minimize these characteristics without reducing their functions. Extensive in vitro and in vivo research has shown that black garlic has several benefits, including anti-oxidant, anti-inflammatory, anticancer, anti-obesity, anti-diabetic, anti-allergic, cardioprotective, and hepatoprotective characteristics. However, it remains unclear which compounds are active ingredients in the extract and the contributions of the main identified compounds to the extract's XO inhibitory activity are unknown. This study aims to look into the potent XO inhibitors found in black garlic methanol extract. The research methodology is experimental, involving the inhibition of xanthine oxidase activity, specifically measuring the amount of uric acid formed during the reaction catalyzed by xanthine oxidase. This is accomplished in vitro via enzymatic reactions and spectrophotometric measurements. The Maillard reaction is responsible for the production of black color in garlic, and it is influenced by heating temperature, humidity, and fermentation time. Starting on the 17th day of the fermentation process, the brownish intensity of the garlic samples heated at 70 ° C and 90% humidity changed to brown. The optimum concentration is 0.3 units/mL at an optimum temperature of 30oC and an optimum pH of 8.0 at a substratum concentration of 0.30 mM at a wavelength of 284 nm. The activity of the xanthine oxidase enzyme was inhibited by allopurinol at various concentrations, with allopurinol having the highest percentage inhibition value of 78.74 percent at a concentration of 10 ppm. The present study showed that meanwhile, the highest inhibition occurred on the 29th day of fermentation, with a percentage value of 68.01 percent, and decreased the next day

Adsorption of Selected Herbicides on Activated Carbon from Single- and Multi-Component Systems-Error Analysis in Isotherm Measurements.

The aim of this study is to examine the influence of various factors on the precision and repeatability of the experimental determination of herbicide adsorption isotherms. Studies were conducted for the activated carbon RIB as an adsorbent and three herbicides as adsorbates: 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chlorophenoxyacetic acid (4-CPA), and 3-chlorophenoxypropionic acid (3-CPP). The herbicide adsorption process was carried out in single-component and multi-component modes (the herbicide was adsorbed in the presence of an accompanying substance, i.e., 4-nitroaniline (4-NA)). Due to the significant contribution of the competition phenomenon in the adsorption process, which is important, e.g., in multi-component environmental systems, a qualitative and quantitative analysis of herbicide adsorption in the presence of a competing substance was presented. This work presents, among other things, the influence of adsorbent heterogeneity (grain size) on measurement uncertainties. The spread of standard deviations for solutions requiring dilution during spectrophotometric measurements was discussed, indicating that dilutions contribute to increasing measurement uncertainties. The heterogeneity parameters of the Freundlich equation for the studied adsorption systems were analyzed; the 2,4-D/RIB system was indicated as the most energetically heterogeneous. Differentiation of the experimental conditions (pH, temperature) allowed us to assess their impact on the efficiency and mechanism of adsorption. A high repeatability of experimental isotherms was obtained for the multi-component system. The accuracy of quantitative determination of equilibrium concentrations for the tested two-component systems was assessed based on the measured UV-Vis spectra, and the adsorption of herbicides from single- and multi-component systems was compared.

Color Modifications of a Maxillofacial Silicone Elastomer under the Effect of Cigarette Smoke.

Although it is known (from the observations of medical professionals) that cigarette smoke negatively affects maxillofacial prostheses, especially through staining/discoloration, systematic research in this regard is limited. Herein, the color modifications of M511 maxillofacial silicone, unpigmented and pigmented with red or skin tone pigments, covered with mattifiers, or with makeup and mattifiers, and directly exposed to cigarette smoke, were investigated by spectrophotometric measurements in the CIELab and RGB color systems. The changes in color parameters are comparatively discussed, showing that the base silicone material without pigmentation and coating undergoes the most significant modifications. Visible and clinically unacceptable changes occurred after direct exposure to only 20 cigarettes. By coating and application of makeup, the material is more resistant to color changes, which suggests that surface treatments provide increased protection to adsorption of the smoke components. The dynamic water vapor sorption (DVS) measurements indicate a decrease of the sorption capacity in pigmented versus unpigmented elastomers, in line with the changes in color parameters.

Stress factors and cytotoxic and genotoxic action of ethanol in Saccharomyces cerevisiae

In industrial fermentation, Saccharomyces cerevisiae are exposed to different stress conditions. In this sense, the aim of this study was to evaluate the toxic action of ethanolic stress on Saccharomyces cerevisiae. Exploratory research was carried out on the stress factors that cause injuries in yeast. Fermentation tests were conducted with the Fleischmann® and Pedra-2 strains, cultivated in sugarcane juice at 22 ºBrix and pH 5.0, adding concentrations of 5, 10, and 15% of ethyl alcohol, and incubated at 30°C at 250 rpm for 10 hours. For the cytotoxic tests, 100 µl of samples were collected for evaluation of cell growth by spectrophotometric measurements at 570 nm, and 5 µl were dripped into Petri dishes containing 2% YPD solid medium and incubated at 30ºC for 72 hours for colony growth. For the genotoxicity test, the comet test was used with 0.5 µl of the samples added to slides previously prepared and subjected to electrophoretic running and subsequently stained in a 0.1% silver nitrate solution. 100 random nucleotides were evaluated, evaluating five DNA damage classes (0, 1, 2, 3, and 4) according to the intensity and pattern of genetic material entrainment. The results show that stress factors interfere with yeast performance. Fleischmann® showed sensitivity to ethanolic stress.

A Calibration Strategy for Silicon Nanowire Field-Effect Transistor Biosensors and Its Application in Ultra-Sensitive, Label-Free Biosensing.

The silicon nanowire field-effect transistor (SiNW FET) has been developed for over two decades as an ultrasensitive, label-free biosensor for biodetection. However, inconsistencies in manufacturing and surface functionalization at the nanoscale have led to poor sensor-to-sensor consistency in performance. Despite extensive efforts to address this issue through process improvements and calibration methods, the outcomes have not been satisfactory. Herein, based on the strong correlation between the saturation response of SiNW FET biosensors and both their feature size and surface functionalization, we propose a calibration strategy that combines the sensing principles of SiNW FET with the Langmuir-Freundlich model. By normalizing the response of the SiNW FET biosensors (ΔI/I0) with their saturation response (ΔI/I0)max, this strategy fundamentally overcomes the issues mentioned above. It has enabled label-free detection of nucleic acids, proteins, and exosomes within 5 min, achieving detection limits as low as attomoles and demonstrating a significant reduction in the coefficient of variation. Notably, the nucleic acid test results exhibit a strong correlation with the ultraviolet-visible (UV-vis) spectrophotometer measurements, with a correlation coefficient reaching 0.933. The proposed saturation response calibration strategy exhibits good universality and practicability in biological detection applications, providing theoretical and experimental support for the transition of mass-manufactured nanosensors from theoretical research to practical application.

Exploring Corbières red wine typicity: evaluation of the impact of winemaking processes on the chemical composition and organoleptic properties of wines from different terroirs

Aromatic and polyphenolic compounds play an important role in the quality of red wines, contributing not only to flavour, but also to colour, astringency and bitterness. To explore the influence of climate and oenological practices on the chemical and sensory profile of wines, red blends from five terroirs of the Corbières appellation were analysed, taking into account two production years (2018 and 2019). The wines were a blend of at least two of four main grape varieties: Syrah, Grenache, Carignan and Mourvèdre. Volatile compounds were evaluated by HS-SPME-GC-MS, while wine pigments and derived pigments were evaluated by spectrophotometric measurements. In addition, the wines were compared using a quantitative descriptive analysis sensory profile method. The percentage of the blend significantly influenced the polyphenolic and aromatic characteristics of the wines, showing distinct 'typicity' characteristics between sub-regions. Maceration techniques, on the other hand, did not did not allow us to discriminate between sub-regions, but enabled a better understanding of chemical and sensory differences between samples.

Application of MTT assay for probing metabolic activity in bacterial biofilm-forming cells on nanofibrous materials

The quantification of cellular metabolic activity via MTT assay has become a widespread practice in eukaryotic cell studies and is progressively extending to bacterial cell investigations. This study pioneers the application of MTT assay to evaluate the metabolic activity of biofilm-forming cells within bacterial biofilms on nanofibrous materials. The biofilm formation of Staphylococcus aureus and Escherichia coli on nanomaterials electrospun from polycaprolactone (PCL), polylactic acid (PLA), and polyamide (PA) was examined. Various parameters of the MTT assay were systematically investigated, including (i) the dissolution time of the formed formazan, (ii) the addition of glucose, and (iii) the optimal wavelength for spectrophotometric determination. Based on interim findings, a refined protocol suitable for application to nanofibrous materials was devised. We recommend 2 h of the dissolution, the application of glucose, and spectrophotometric measurement at 595 nm to obtain reliable data. Comparative analysis with the reference CFU counting protocol revealed similar trends for both tested bacteria and all tested nanomaterials. The proposed MTT protocol emerges as a suitable method for assessing the metabolic activity of bacterial biofilms on PCL, PLA, and PA nanofibrous materials.

Effect of Film Thickness on the Electrical Resistivity and Optical Functions Distribution of Iron Tris(8-hydroxyquinoline) Thin Films

Iron tris(8-hydroxyquinoline) (Feq3) was synthesized and investigated by X-ray photoemission spectroscopy. It crystalizes in triclinic polycrystalline structure in powder form, whereas the Feq3 films, with different thickness values (12, 20, 35, and 42 nm), have an amorphous structure. The influence of film thickness on the electrical resistivity and the optical properties is reported. The morphology of Feq3 was investigated in terms of field-emission scanning electron microscope. Electrical resistivity measurements indicate an inverse proportionality to the film thickness. The optical properties of Feq3 films were investigated in terms of photoluminescence spectra and spectrophotometric measurements of transmittance and reflectance. The optical functions such as absorption coefficient and refractive index of the films were calculated. The dependence of the Feq3 film thickness on the optical energy band gap and dispersion parameters was studied. The outcomes indicate that the Feq3 films are of great importance for applications in organic solar cells and light emitting diodes.

Analysis of CeO2/SiO2 double-layer thin film stack with antireflection effect for silicon solar cells

This study introduces CeO2/SiO2 double-layer film stacks and its antireflection coating effect. Optical properties were analyzed by spectrophotometer measurements; surface morphology and cross-sections were observed by Scanning Electron Microscopy (SEM); elemental distributions and crystallographic properties were determined by Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD) measurements. Average reflectance of single-layer 0.3MSiO2, 0.6MSiO2, and 0.3MCeO2 thin films were 30.54%, 20.12%, and 14.23%, respectively. Average reflectance was decreased significantly down to 5.9% by 0.3MCeO2/0.6MSiO2 double-layer thin films comparing to those of the results of single-layer films and bare silicon surface reflection (~40%). Antireflective effect of the films on solar cells was estimated by simulation using the measured reflection data. Simulated solar cells indicate that 0.3MCeO2/0.6MSiO2 double-layer antireflective coatings are capable to increase the efficiency significantly and conversion efficiency of 21.7% could be achieved.

Theranostic dye entrapped in an optimized blended-polymer matrix for effective photodynamic inactivation of diseased cells.

Despite the wide range of treatment options available for cancer therapy, including chemotherapy, radiation therapy, and surgical procedures, each of these treatments has a different side-effect profile and leaves the patient with no option but to choose. Due to their insensitivity and nonspecificity, conventional treatments damage normal cells together with cancer cells. In recent years, a significant amount of attention has been focused on photodynamic therapy (PDT) as a treatment for cancer and drug-resistant microbes. An activated photosensitizer is used as a part of the procedure along with oxygen molecules and a specific wavelength of light belonging to the visible or NIR spectral zone. A light-sensitive laser dye, rhodamine 6G (R6G), was used in the present study as a photosensitizer, taking a challenge to improve the aqueous solubility and ROS quantum yield using optimum concentration (160mg/ml) of chitosan-alginate (Cs-Alg) blended polymeric nanoformulations. As evidenced by steady-state spectrophotometric and fluorometric measurements, ROS quantum yield increases three-fold over aqueous solution along with solubility gaining that was validated by PDT experiment using human epithelial carcinoma (KB) cell line. Phantom optical imaging was taken using the IVIS imaging system to establish the formulations as a fluorescence-based optical contrast agent, and zebrafish embryos were used to establish their safe in vivo use. The release profile of R6G was fitted using kinetic models, which followed the Non-Fickian kinetic profile. In conclusion, we recommend the formulations as a potential theranostic agent that will aid in PDT-based therapy in conjunction with optical imaging-based diagnosis.

Photoactive metabolite mediated photodynamic therapy of Rhabdomyosarcoma cell lines using medicinal plants and Doxorubicin co-treatments

BackgroundMedicinal plant-mediated combinational therapies have gained importance globally due to minimal side effects and enhanced treatment outcomes compared to single-drug modalities. We aimed to analyze the cytotoxic potential of each conventional treatment i.e., photodynamic therapy (PDT), chemotherapy (doxorubicin hydrochloride; Dox-HCl) with or without various concentrations of medicinal plant extracts (PE) on soft tissue cancer Rhabdomyosarcoma (RD) cell line.MethodsThe Rhabdomyosarcoma (RD) cell line was cultured and treated with Photosensitizer (Photosense (AlPc4)), Chemo (Dox-HCl), and their combinations with different concentrations of each plant extract i.e., Thuja occidentalis, Moringa oleifera, Solanum surattense. For the source of illumination, a Diode laser (λ = 630 nm ± 1 nm, Pmax = 1.5 mW) was used. Photosensitizer uptake time (∼ 45 min) was optimized through spectrophotometric measurements (absorption spectroscopy). Drug response of each treatment arm was assessed post 24 h of administration using 3-(4, 5-dimethyl-2-thiazolyl)-2, 5- 5-diphenyl-2 H- tetrazolium bromide (MTT) assay.ResultsPE-mediated Chemo-Photodynamic therapy (PDT) exhibited synergistic effects (CI < 1). Moreover, Rhabdomyosarcoma culture pretreated with various plant extracts for 24 h exhibited significant inhibition of cell viability however most effective outcomes were shown by low and high doses of Moringa oleifera compared to other plant extracts. Post low doses treated culture with all plant extracts followed by PDT came up with more effectiveness when compared to all di-therapy treatments.ConclusionThe general outcome of this work shows that the ethanolic plant extracts (higher doses) promote the death of cancerous cells in a dose-dependent way and combining Dox-HCl and photo-mediated photodynamic therapy can yield better therapeutic outcomes.

Determination of Nicotine in Juices, Soft and Energy Drinks collected from Libyan Local Markets Using UV–Visible Spectrophotometer

This study aims to determine the nicotine in juices, soft and energy drinks using a UV-Visible spectrophotometer. In the presented study, sixteen samples (four juices, seven soft drinks, and five energy drinks) are collected from local markets in El-Beida - Libya. A rapid, simple, and reliable extraction method is developed and validated for the determination of nicotine in the samples under study using spectrophotometric methods. The method is validated over a wide linear range of 1.62–81.06 µg/mL with correlation coefficients being consistently greater than 0.9999 by UV-Visible Spectrophotometer. The minimum nicotine level was observed in the juices samples, while the energy drinks samples showed the highest nicotine content. The spectrophotometric measurement indicates that the results of nicotine concentrations in juices samples are in the range of 0.3233 - 0.5238 µg/mL, whereas its concentrations in soft drinks samples are in the range of 0.7251 - 0.9949 µg/mL, and the concentrations in energy drinks samples are in the range of 0.8521 - 1.3471 µg/mL. The criteria considered for validation are linearity, the limit of detection, and the limit of quantitation. The nicotine contents in all the samples analyzed in our study were below the allowable limits set by the US Food and Drugs Administration.

Ensemble Variability Properties of Active Galactic Nuclei in the SDSS DR17

We present the results from a study of ∼9600 broadline-selected active galactic nuclei (AGNs) with host galaxies detected from the Sloan Digital Sky Survey (SDSS) Data Release 17. We compute ensemble variability statistics based on a comparison of the original SDSS photometric data with spectrophotometric measurements obtained days to decades later in the Sloan g, r, and i bands. Galaxy and AGN templates have been fitted to the SDSS spectra to isolate the AGN component from the host galaxy. The sources have absolute magnitudes in the range −24 < M i < −18 and lie at redshifts less than z ∼ 0.9. A variability analysis reveals that the anticorrelation between luminosity and variability amplitude continues down to log(Lbol [erg s−1]) = 43.5, demonstrating that the relationship extends by 4 orders of magnitude in AGN luminosity. To further explore the connection between AGN luminosity and variability, we determine the black hole mass and the accretion rate through measurement of the Hβ line width and the monochromatic luminosity at rest frame 5100 Å. Our results suggest that the accretion rate is the dominant parameter impacting the amplitude of variability and that the anticorrelation between the accretion rate and amplitude extends to rates as low as 1% Eddington. Moreover, we also identify an anticorrelation between the variability amplitude and black hole mass, with the correlation appearing strongest among the AGNs with low accretion rates.

THE SIMULTANEOUS SPECTRAL DETERMINATION OF CANDESARTAN CILEXETIL AND HYDROCHLOROTHIAZIDE IN TABLETS USING THE TRIVARIATE CLASSICAL LEAST SQUARES METHOD

Objective: Candesartan cilexetil (CDS) is a member of the sartan group of drugs and is widely used to lower blood pressure. Hydrochlorothiazide (HCT) is the most commonly used diuretic group of drugs and is prescribed together with candesartan cilexetil in cases where blood pressure cannot be reduced. Pharmaceutical preparations containing these two active compounds in combination are preferred today to provide a more effective pharmacological effect. Therefore, it is of great importance to determine the quantities of these combined pharmaceutical preparations with new analytical methods that are fast, easy, and sensitive in quality control and routine analysis. In this study, a new trivariate classical least squares calibration method (TCLS) was developed for the simultaneous quantification of candesartan cilexetil (CDS) and hydrochlorothiazide (HCT) in binary mixtures and commercial tablets without using a preliminary separation step. Material and Method: CDS and HCT compounds were kindly donated by National Pharm Ind., Turkey. HPLC-grade methanol (J.T. Baker, Netherlands) was used as a solvent for the spectrophotometric analysis. In the application of the TCLS method, the determination and quantification of CDS and HCT were carried out using UV spectrophotometric measurements with 1 cm quartz cells in the 200-310 nm spectral region (slit range 2 nm). The newly developed TCLS method was tested using a validation set consisting of eight synthetic mixture solutions within the working ranges of 4.0-20.0 μg/ml for CDS and HCT. Simultaneous quantification analyses of CDS and HCT were performed on ATACAND PLUS® Tablet supplied by Astra Zeneca İlaç Ltd Şti. Result and Discussion: The method is based on the application of TCLS to the absorbance measurements at three different wavelength points (223.5, 240.0, and 268.5 nm). The absorptivity values (µg-1mlcm-1) of pure CDS and pure HCT were 6.67x10-2, 2.76x10-2, 2.33x10-2, and 11.41x10-2, 0.46x10-2, 6.42x10-2 at the selected wavelengths, respectively. Recovery values and relative standard deviation values were calculated as 97.2% and 1.61% for CDS and 99.7% and 3.67% for HCT, respectively. This method was successfully applied to the spectrophotometric quantitative analysis of tablets containing CDS and HCT, and then, a good agreement was reported.

Validation Study on Spectrophotometric Measurement of Ethanol from Beer and Non-Alcoholic Beer Samples Distilled by Micro Steam Distillation Method

The method validation technique for determining the ethanol percentage (v/v) in beer and non-alcoholic beer is presented in this study. The underlying idea is to use the micro water vapor method to distill the ethanol from beer and then use the spectrophotometric method, which uses the oxidation of sodium dichromate to measure the amount of ethanol. The Harmonized Guidelines for Single-Laboratory Validation of Methods of Analysis were used to validate the analytical method that we provided. The following aspects of the method were assessed: precision, recovery, linearity, measuring range, detection and quantification limitations, method detection limit, and measurement uncertainty. The following were the limits of detection (LOD) and quantification values (LOQ), and the method detection limit (MDL): ethanol, 0.04%, 0.05%, and 0.15. For both repeatability and within-laboratory reproducibility, the relative standard deviation values were less than 2.36 and 4.12%, respectively. The spiked samples had recovery rates ranging from 97% to 102%. These findings fulfilled the minimal performance standards set forth in AOAC Official Methods of Analysis Appendix F: Guidelines for Standard Method Performance Requirements. As a result, the process can be used for the regular analysis of ethanol in the beer and non-alcoholic beer under study.