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Cryo-electron microscopy (cryo-EM) is a powerful tool for imaging biological samples but is typically limited by sample thickness, which is restricted to a few hundred nanometers depending on the electron energy. However, there is a growing need for imaging techniques capable of studying biological samples up to 10 µm in thickness while maintaining nanoscale resolution. This need motivates the use of mega-electron-volt scanning transmission electron microscopy (MeV-STEM), which leverages the high penetration power of MeV electrons to generate high-resolution images of thicker samples. In this study, we employ Monte Carlo simulations to model electron–sample interactions and explore the signal decay of imaging electrons through thick specimens. By incorporating material properties, interaction cross-sections for energy loss, and experimental parameters, we investigate the relationship between the incident and transmitted beam intensities. Key factors such as detector collection angle, convergence semi-angle, and the material properties of samples were analyzed. Our results demonstrate that the relationship between incident and transmitted beam intensities follows the Beer–Lambert law over thicknesses ranging from a few microns to several tens of microns, depending on material composition, electron energy, and collection angles. The linear depth of silicon dioxide reaches 3.9 µm at 3 MeV, about 6 times higher than that at 300 keV. Meanwhile, the linear depth of amorphous ice reaches 17.9 µm at 3 MeV, approximately 11.5 times higher than that at 300 keV. These findings are crucial for advancing the study of thick biological and semiconductor samples using MeV-STEM. [ABSTRACT FROM AUTHOR]

The present work aimed to develop a simple analytical method and validate the same for the estimation of Voriconazole using ultraviolet spectrophotometry. Methanol and artificial vaginal fluid (AVF) pH 4.1 were chosen as solvents for the development of the analytical method and the validation of the method was done for the different parameters. Voriconazole showed higher absorbance at 256 nm both in methanol and AVF pH 4.1. Linearity, precision, and accuracy as the analytical parameters were studied as per the International Conference of Harmonization (ICH) guidelines. The concentration range of 10–50 μg/mL in methanol and AVF pH 4.1 showed a linear response and followed Beer's law with coefficient correlation values of 0.998 for methanol and 0.999 for AVF pH 4.1. The results for the accuracy and the repeatability parameter presented values that lie within the range of 98–102%, indicating a higher confidence interval. Regarding the method's sensitivity, the LOD for the drug in methanol and AVF pH 4.1 was found to be 2.55 and 2.00 μg/mL, respectively. The LOQ for the drug in methanol was 7.75 μg/mL and in AVF pH 4.1 was 6.08 μg/mL. The proposed, developed and validated method was simple, sturdy, cost-effective, and time-saving. The method could be further applied to calculate the entrapment efficiency of the drug-loaded nanostructured lipid carrier and tablet drug content. [ABSTRACT FROM AUTHOR]

The measurement of vitamin B1 in pure and pharmaceutical formulations was proposed by using a straightforward and sensitive spectrophotometric approach. Sulfacetamide (SFA) is diazotized, then coupled with vitamin B1 in alkaline media to produce a colored azo dye complex with a stability constant of 5.597 × 105 L/mol. The product is stable, with a maximum absorption wavelength of 489.5 nm, molar absorptivity of 10108 L/mol∙cm, Sandell's sensitivity of 0.0334 μg/cm2, detection limit of 0.0135 μg/mL, and Beer's law being observed over the concentration range of 0.2–20.0 μg/mL. The stability constant and stoichiometry of the produced azo dye were calculated using the continuous variation (Job's) and mole ratio methods. The suggested approach was used successfully in the determination of vitamin B1 in its pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

A method with rapid, sensitive, accurate, and selective for estimation of local anesthetic procaine hydrochloride (PRO.HCl) is crucial, due to its bad damage to health if administrated excessively. In this work two spectrophotometric methods oxidative coupling and cloud point extraction (CPE) were utilized for determination of PRO.HCl in its standard state and pharmaceutical preparations. Method A, based on the oxidative coupling reaction using sodium hypochlorite as an oxidant and 2,5-dimethylphenol as coupling agent. The blue colored product has high absorption at 600 nm. Method B based on the CPE relying on the previous reaction, with addition of Triton X-114, after extracting the colored product, it was measured at 630 nm. Beer's law of both methods are linear in the concentration ranges 2.50-50 µg/mL (method A) and 1.25-3.75 µg/mL (method B). The molar absorptivity coefficients of methods (A) and (B) are 4.01 x 103 and 1.34 x 104 L/mol.cm, respectively. For (method A) limit of detection and limit of quantification were calculated and found that 0.26 µg/mL and 0.87 µg/mL, respectively, while for (method B) were found to be 0.16 and 0.54 µg/mL, respectively. Both methods (A and B) are applied to evaluate PRO.HCl in pharmaceutical preparations (injection). [ABSTRACT FROM AUTHOR]

Diabetes is a fast-developing medical issue that causes most renal and cardiac illnesses. Thus, diabetes management requires regular glucose monitoring. One potential technology is non-invasive glucometer monitoring. This work aims to develop a user-friendly near-infrared sensor-based non-invasive glucose monitoring system, correlating sensor output voltage variations with glucose levels, to provide accurate and convenient glucose monitoring for diabetes management. The objective is to validate the system's accuracy against existing fingerpick methods and analyze its performance across different age groups and food intake conditions through experimental testing and Clarke grid analysis. In our research, we propose a near-infrared sensor-based non-invasive-type glucose monitoring technique which is a user-friendly system. The experimental setup and prototype system are designed and implemented for measuring the variation of glucose level with respect to a sensor output voltage. Using Beer Lambert's law, the established results correlated the absorbance property of light with the sample concentration level. Demonstration of testing for different aged people was done under various food intake conditions. The obtained results are tabulated and validated with the existing fingerpick method and achieved an accuracy of 97.8%. Also, Clarke grid analysis has been done and depicted the pattern obtained. [ABSTRACT FROM AUTHOR]

Solution concentration detection plays a crucial role in research, education, and industrial applications. To address the complexity, time consumption, and high costs associated with traditional methods, this study introduces a color-based solution concentration detection method. The method employs a simplified device to capture solution color, mitigates the effects of ambient light, and utilizes a system for solution color image recognition based on the Lambert-Beer law and image colorimetry. Using OpenCV (Open Source Computer Vision Library), images of solutions with varying concentrations are processed to establish a regression model correlating HSV (Hue, Saturation, Value) color features with solution concentrations, enabling accurate measurement. Experimental results demonstrate strong linear correlation (R² = 0.99) between HSV values and concentrations, particularly with copper sulfate solutions ranging from 0 to 50 mg∙mL-1. This method offers a novel solution for quality control in industrial production and enhances educational experiments. Furthermore, the adaptable design of the detection device facilitates measurement of additional solution parameters, including pH, expanding its utility in diverse applications. [ABSTRACT FROM AUTHOR]

Abstract Optical density (OD) is an important indicator of microbial density, and a commonly used variable in growth curves to express the growth of microbial culture. However, OD values show a linear relationship with bacterial concentration only at low concentrations. When the cell density is high, the relationship loses linearity, and serial dilution is needed to obtain readings of better accuracy. Here, we show that measuring OD values using shorter light paths is in close equivalence to measuring OD values of the cell culture with corresponding dilution. By measuring three different light paths simultaneously, accurate OD values can be easily obtained from low to high cell density. Using this method, growth curves of Escherichia coli, Staphylococcus aureus, and Pichia pastoris are measured with higher accuracy. To further simplify the process, an L‐shaped cuvette and a corresponding turbidimeter are designed specifically for OD value measurement based on the multi‐light path transmission method.

The presented article is devoted to the study of oil-collecting and oil-dispersing properties of the quaternary ammonium salt (DAD), formed by hexadecane (6-DT) and heptadecanoic acid (7-DT) with triethanolamine (TEA) {triethanolammonium salt of hexadecanoic acid (6-DAD) and triethanolammonium salt of heptadecanoic acid (7-DAD)}, as well as its use as an analytical reagent for the extraction-photometric determination of manganese in the form of a mixed-ligand complex (MLC) with 2-hydroxy-5-chlorothiophenol (H2L, L) and DAD in various objects. DAD solutions with a concentration of 0.025%, 0.05%, 0.75%, 0.1% form a colloidal solution in water, and are readily soluble in ethyl and isopropyl alcohols. From a comparison of DADs, it is clear that 6-DAD is superior in its ability to disperse oil in drinking and sea water (6-DAD: CD=82.2; 7-DAD: 86.2%). 6-DAD exhibited high surface activity, showing a decrease in surface tension from 62.2 mN/m to 34.4 mN/m (and for 7-DAD from 59.8 mN/m to 33.3 mN/m). DAD was studied as an oil collector and oil dispersant when treating the surface of water that was turbid due to an oil layer 0.17 nm thick. The spectrophotometric method was used to study the complex formation of manganese(II) with L and DAD. The maximum absorption of MLC Mn(II)-L-DAD is observed at λ = 545-550 nm (pHop.3.5-5.9). The molar absorption coefficients range from (2.58-2.71)·104. With a single extraction using chloroform, 99.1-99.3% of manganese is extracted as MLC. The optimal conditions for the formation and extraction of MLC are 1.3·10-3 M L and (1.2-1.5)·10-3 M-DAD. Beer's law is followed within the range of 0.2-100 µg/mL of manganese. Large amounts of alkali, AEM, and REE do not interfere with the determination of manganese. The interfering effect of Fe(III) was eliminated using thioglycolic acid or a 20% solution of SnCl2, Cu(II) and Cr(VI) were addressed with thiourea, Ti(IV) was treated with ascorbic acid, and Zr(IV), Nb(V), and Ta(V) with fluoride ions. The results of the studies on the formation and extraction of Mn(II) MLC with L and DAD were applied for the extraction-photometric determination of manganese in water. [ABSTRACT FROM AUTHOR]

An accurate and cost-effective method utilizing continuous flow injection spectroscopy has been developed for analyzing oxymetazoline hydrochloride in pharmaceutical and bulk powder forms. This new method involves reacting drug in an alkaline solution with diazotized 4-chloroaniline to produce an orange dye with a maximum absorption at λmax of 483 nm. The flow injection analysis approach was extensively studied in terms of both chemical and physical characteristics to achieve high sensitivity. Within a concentration range of 50-150 μg/mL and a detection limit of 10.4 μg/mL, oxymetazoline hydrochloride follows Beer's law when the experimental variables are optimized. The method's effectiveness was confirmed by achieving high reproducibility of less than 2% (n = 5). A statistical analysis comparing the proposed method to the standard spectrophotometric technique using F and t tests shown no significant differences in accuracy and precision. Additionally, the analytical greenness assessment and the green analytical procedure index were applied to assess the method's greenness and the results demonstrated that the flow injection analysis method satisfies the criteria of green analytical methodologies. [ABSTRACT FROM AUTHOR]

Voriconazole, a pivotal antifungal agent, has been analysed using two uncomplicated, sensitive, rapid, and validated spectrophotometric methods. These procedures rely on the formation of charge transfer complexes in methanol, employing alizarin red S and quinalizarin as chromogenic reagents, each exhibiting absorption maxima at 568 and 513 nm, respectively. The optimisation of reaction conditions was explored, encompassing the choice of solvent, reagent concentration, and reaction duration. Both alizarin red S and quinalizarin demonstrated excellent adherence to Beer's law over concentration ranges of 1.0-18 and 1.0-24 µg mL-1, respectively, with robust correlation coefficients (r² ≥ 0.9993) and minimal relative standard deviations (RSD% ≤ 1.04). Additionally, calculations were conducted for molar absorptivity (1.1256x104 and 1.7624 x104 L mol-1 cm-1), Sandell sensitivity (31.0 and 19.82 ng cm-2), detection and quantification limits (0.3 and 1.0 µg mL-1) for alizarin red S and quinalizarin, respectively. Both methods were effectively applied for the determination of voriconazole in dosage forms, and their validity was confirmed using the standard addition technique. The results obtained from these proposed procedures for pure and dosage forms closely matched those from previously reported methods. [ABSTRACT FROM AUTHOR]

We investigate the effects of spatially non-uniform radio-frequency electric (E) field amplitudes on the spectral line shapes of electromagnetically induced transparency (EIT) signals in Rydberg atomic systems used in electrometry (i.e., the metrology of E-field strengths). Spatially non-uniform fields distort the EIT spectra from that of an ideal case, and understanding this distortion is important in the development of Rydberg atom-based sensors, as these distortions can limit accuracy and sensitivity. To characterize this distortion, we present a model that approximates the atom vapor as multi-layered media and then uses Beer's law to combine the absorption through its many discrete thin segments. We present a set of expected line distortions caused by various RF electric-field distributions found in practice. This provides an intuitive diagnostic tool for experiments. We compare this model to measured experimental atomic spectra in both two-photon and three-photon excitation schemes in the presence of non-uniform radio-frequency fields. We show that we can accurately model and reproduce the EIT lineshape distortion observed in these experimental data. [ABSTRACT FROM AUTHOR]

The article from the journal "Analytical & Bioanalytical Chemistry" discusses the importance of incorporating dialogue into laboratory teaching practices in the context of chemistry education. It emphasizes the benefits of dialogue in facilitating learning, supporting student engagement, and enhancing scientific thinking skills. The article provides practical examples of how dialogue can be formalized in laboratory teaching, such as through structured discussions at the beginning of laboratory sessions and dialogue prompts in laboratory manuals. By promoting dialogue, educators aim to create a supportive and immersive learning environment that fosters meaningful interactions between students and instructors. [Extracted from the article]

Soft materials that respond to external stimuli are promising candidates for next-generation actuators with human-friendly nature1,2. Among various stimuli to induce strain, light offers spatial selectivity, which allows versatile motion of a continuous body. However, spatial selectivity of photoactuation has been limited in two dimension due to the predominant absorption of photons by chromophores near a light source in accordance with Beer-Lambert law. Here, we report the deformation of crosslinked liquid-crystalline polymer films triggered by two-photon absorption. The films containing azotolane moieties show photoinduced deformation upon irradiation with fs laser pulses through two-photon absorption. The direction of photoinduced bending is controlled by depth-selective excitation with a focused laser beam. Furthermore, the mode of deformation is transformed from bending to twisting by irradiating spots near an edge of the film. Inhomogeneous photoirradiation with high spatial selectivity allows an infinite variation of three-dimensional motions even apart from preprogrammed behavior, which would be advantageous especially in application to microactuators. Spatial selectivity of photoactuation in soft material has been limited in two dimension and three-dimensionally selective actuation is an effective approach to control the direction and types of macroscopic motions. Here, the authors report the photoinduced deformation of liquid-crystalline polymer films with high spatial selectivity via a two-photon absorption process. [ABSTRACT FROM AUTHOR]

Background The formation of charge-transfer complexes (CTCs) of iodine with five chemotherapeutic drugs used for the treatment of different types of cancer has not been investigated. These drugs are olaparib, seliciclib, vandetanib, dasatinib, and tozasertib. Additionally, these drugs need an appropriate general spectrophotometric assay for their analysis in the dosage forms regardless of the differences in their chemical structures. Objective The aim of this study was the development of a novel microwell spectrophotometric assay (MW-SPA) for one-step determination of these drugs via their interactions with iodine, which resulted in instantaneous production of bright lemon-yellow CTCs. Methods A spectrophotometric study of the CTCs was conducted, and all CTCs were characterized. Site(s) of interaction on each drug were assigned, and the MW-SPA was developed and applied to the analysis of dosage forms. Results The findings confirmed that the reactions proceeded via CTC formation. Beer's law was obeyed over a general concentration range of 1–6 µg/mL. The LODs and LOQs were in the ranges of 0.5–2.1 and 1.5–6.4 µg/mL, respectively. The proposed MW-SPA demonstrated excellent precisions as the relative standard deviations were < 2.24 and 2.23% for the intra- and inter-assay precision, respectively. Recovery studies demonstrated the accuracy of MW-SPA. Successful determination of all drugs in bulk and tablet forms was achieved using the MW-SPA. The environmental sustainability of the proposed methodology was determined, providing evidence of the assay's alignment with the basis of green analytical chemistry. The high throughput of the assay was documented. Conclusion In contrast to other existing methods, the MW-SPA described herein was valid for analyzing all drugs at the same wavelength. Highlights The assay is useful for routine analysis of drugs in their formulations in QC laboratories. [ABSTRACT FROM AUTHOR]

This article presents a low-cost photometer for experimental teaching designed to determine hexavalent chromium in aqueous solutions based on the detection of yellow chromate ions with ultraviolet light at 373 nm. This procedure replaces the colorimetric method that uses a spectrophotometer for the detection of the red-violet 1.5-diphenylcarbazide complex at 540 nm. To demonstrate the operation of the photometer, the Beer-Lambert law was evaluated using the linear regression technique, and the absorbance values obtained by the photometer were compared with those of a Shimadzu UV-2600 series UV-Vis spectrophotometer in five samples of hexavalent chromium in the range of 1 - 25 mg L-1. The experimental results demonstrated the linearity required by the Beer-Lambert law with a determination coefficient of 0.9988, and similarity between both analytical instruments with a relationship of 1.0041 between the absorbance values with a determination coefficient of 0.9993. In conclusion, the low-cost photometer is an excellent proposal for teaching the Beer-Lambert law in the classroom because it reduces the formation of waste, and dispenses with the reagents of the colorimetric method. [ABSTRACT FROM AUTHOR]

An innovative, meticulously crafted, targeted, expeditious, precise, and cost-effective methodology was pioneered utilizing UV-Vis spectrophotometry for the quantitative determination of Mirabegron in both its pristine state and pharmaceutical tablet formulation. Following thorough deliberation on factors such as solubility, stability, toxicity, and carcinogenicity, petroleum ether emerged as the solvent of choice, aligning with the principles of environmentally conscious methodology. The absorption maxima were unequivocally detected at a wavelength of 250 nm, making petroleum ether the solvent of choice. The method adheres faithfully to Beer's law within a concentration range spanning from 0.004 to 0.016 mg/mL, boasting a remarkable correlation coefficient of 0.9945. LOD and LOQ were meticulously computed from the dataset, yielding values of 0.0001663 and 0.0005039, respectively. The relative standard deviation, meticulously derived from the dataset, stands at less than 2%. Moreover, in the rigorous accuracy assessment, Mirabegron's recovery percentage fell impressively within the narrow band of 98.62 to 101.46%. During both the intraday and interday precision evaluations, the %Assay remained consistently within the stringent range of 99.63 to 101.12%, affirming the method's precision. Furthermore, adherence to the rigorous guidelines outlined in ICH Q2 (R1) was ensured throughout the comprehensive validation process, consolidating the method's credibility and suitability for analytical applications. [ABSTRACT FROM AUTHOR]

Significance: Broadband near-infrared spectroscopy (bbNIRS) is useful for the quantification of cerebral metabolism. However, its usefulness has not been explored for broad biomedical applications. Aim: We aimed to quantify the dynamic responses of oxidized cytochrome c oxidase (Δ[oxCCO]) within the mitochondria to arterial occlusion and the dynamic correlations between hemodynamic (Δ[HbO]) and Δ[oxCCO] responses during and after occlusion in forearm tissues. Approach: We recruited 14 healthy participants with two-channel bbNIRS measurements in response to a 5-min forearm arterial occlusion. The bbNIRS system consisted of one shared white-light source and two spectrometers. The modified Beer-Lambert law was applied to determine the occlusion-induced changes in Δ[oxCCO] and Δ[HbO] in the shallow- and deep-tissue layers. Results: During the 5-min occlusion, dynamic responses in hemodynamics exhibited the expected changes, but Δ[oxCCO] remained constant, as observed in the 1- and 3-cm channels. A linear correlation between Δ[HbO] and Δ[oxCCO] was observed only during the recovery phase, with a stronger correlation in deeper tissues. The observation of a constant Δ[oxCCO] during the cuff period was consistent with two previous reports. The interpretation of this observation is based on the literature that the oxygen metabolism of the skeletal muscle during arterial occlusion remains unchanged before all oxy-hemoglobin (and oxy-myoglobin) resources are completely depleted. Because a 5-min arterial occlusion is not adequate to exhaust all oxygen supply in the vascular bed of the forearm, the local oxygen supply to the muscle mitochondria maintains redox metabolism uninterrupted by occlusion. Conclusions: We provide a better understanding of the mitochondrial responses to forearm arterial occlusion and demonstrate the usefulness of bbNIRS. [ABSTRACT FROM AUTHOR]

The earliest silicon-based aerogels attracted attention due to their nanoscale porous structure and high transparency. Still, they need to be more balanced with the poor mechanical properties. Their brittle structure limits the development of this promising new material. Therefore, the goal of this work is to optimize the mechanical properties of aerogels while maintaining transparency. The good mechanical properties of polymers have made them the material of choice for this work. Polyvinyl alcohol (PVA), which can undergo self-crosslinking through side-chain hydroxyl groups forming hydrogen bonds, was chosen as the raw material to simplify and expedite the production process. The production process was experimented with, analyzed, and refined. Considering the time efficiency of the experimental process, a one-step gelling method was invented to facilitate the sol-gel transition. The one-step gelling method maintained the high transparency of PVA aerogels and reduced the time required for the gelation process compared to the freeze-thawing method. This work employs carbon dioxide supercritical drying to ensure minimal structural collapse and maximize the porous structure's retention. The transmittance of PVA aerogels can reach up to 93.67% at a wavelength of 1333 nm. The internal structure of aerogels with different PVA concentrations was observed using a Scanning electron microscope. Applying Beer-Lambert's Law eliminated the effect of sample thickness on transparency. The relationship between the transparency of PVA aerogels, their microstructure, and macroscopic concentration was studied and analyzed for the first time. While ensuring light transmittance, the modulus of the PVA aerogel reached as high as 6.18 ± 0.56 MPa at 13 wt%. [ABSTRACT FROM AUTHOR]

This study focuses on the interaction between albendazole and iron, forming a complex that exhibits unique properties. The albendazole-iron complex shows a maximum absorbance at 420 nm, indicating a strong interaction between the two components. This interaction results in a molar absorptivity, a measure of how strongly the complex absorbs light at a given wavelength, of 1 x 10³ L mol-¹ cm-¹. The complex follows Beer's law, a fundamental concept in spectroscopy, within a concentration range of 0.082 -- 0.82 μg mL-1. This means that the absorbance is directly proportional to the concentration of the complex in this range, allowing for accurate determination of albendazole concentration in a sample. The sensitivity of this method, as indicated by Sandell's sensitivity, is 0.266 μg mL-1. This means that changes in concentration as small as 0.266 μg mL-1 can be detected, making this method highly sensitive. Furthermore, the limit of detection (LOD), the smallest concentration that can be reliably measured, is 0.067 μg mL-1. The limit of quantification (LOQ), the lowest concentration that can be accurately quantified, is 0.20 μg mL-1. These values indicate that this method can reliably detect and quantify even small concentrations of albendazole. The effectiveness of this method has been demonstrated by determining albendazole in commercial tablets. This suggests that this method could be widely applicable for the analysis of albendazole in various pharmaceutical formulations, contributing to quality control and assurance in the pharmaceutical industry. [ABSTRACT FROM AUTHOR]

The complexation interaction between arsenazo III chromogenic agent and tetravalent thorium ion (Th4+) is the theoretical basis for the determination of thorium by spectrophotometry. In this paper, the effects of the acidity, temperature, interfering ions and Th4+ concentration on the absorbance and stability of arsenazo III-Th4+ solution by spectrophotometry were systematically studied. The results showed that the solutions to be tested had high absorbance values and stability only when the concentration of hydrochloric acid was greater than 6 mol·L−1. The absorbance decreased only 0.02 when the temperature was changed from 15°C to 40°C. The absorbance of arsenazo III-Th4+ solution at 662 nm showed a good linear relationship with the concentration of Th4+ under the same experimental environment (R2 = 0.9986), and the apparent molar absorption coefficient was 9.95 × 104 L·mol−1·cm−1, showing that thorium can be accurately quantitatively measured according to the Lambert-Beer law under these conditions. [ABSTRACT FROM AUTHOR]

Nowadays, there is a need to expand the bank of spectrophotometric methods for the determination of perindopril in dosage forms for the purposes of routine pharmaceutical analysis, which would be simple, express, «green» and inexpensive. In the present work, perindopril in tablets was quantified via a direct simple, «green», and non-extracting spectrophotometric approach based on the formation of ion-pair complexes with sulphophtalein dyes. The absorbances of the colored reaction products were registered at 405 nm (bromocresol green, BCG), 397 nm (bromocresol purple, BCP, and bromothymol blue, BTB) and 598 nm (bromophenol blue, BPB). To achieve the highest intensity of absorbance, optimum conditions were established by the screening of many experimental factors such as optimal concentration and volume of dyes, and the time consumed for the reaction. Beer's law was obeyed in the ranges of 0.44–3.96 µg/mL (BCG), 3.00–7.00 µg/mL (BCP), 4.00–12.00 µg/mL (BTB) and 0.44–3.52 µg/mL (BPB). All four methods were validated in accordance with ICH guidelines, confirming specificity and linearity, accuracy and precision, limits of detection and quantification, robustness. These validated methods provide a reliable and green approach for the quantitative analysis of perindopril in tablets, contributing to safer and more sustainable laboratory practices in pharmaceutical analysis. [ABSTRACT FROM AUTHOR]

A new simple, precise, and sensitive charge transfer method for estimation of tioconazole drug in pure form and Gyno-Trosyd tablet was developed based on the reaction of the n-electron donor tioconazole drug with π-receptors, namely chloroanilic acid, 2,3-dichloro-5,6-dicyano-1,4-benzoquinon, and picric acid. The complexes were determined spectrophotometrically at 460, 402, and 520 nm for the tioconazole-2,3-dichloro-5,6-dicyano-1,4-benzoquinon, tioconazole-picric acid, and tioconazole-chloroanilic acid complexes, respectively. The conditions under which experiments should be conducted have been extensively studied. Beer's law was obeyed over the working concentration ranges of 10–100, 10–250, and 2–140 μg/mL for tioconazole-2,3-dichloro-5,6-dicyano-1,4-benzoquinon, tioconazole-chloroanilic acid, and tioconazole-picric acid complexes, respectively. [ABSTRACT FROM AUTHOR]

For dye-sensitized solar cells (DSSC), the material properties and design parameters of their photoanodes have a more significant impact on the performance of DSSCs. In order to investigate this issue in depth, this paper adopts numerical simulation to explore the detailed impact of change in the photoanode structure on the performance of DSSC. However, the current mathematical model is not comprehensive enough and the prediction accuracy is low. Therefore, based on the theory of photoelectron transfer and Lambert Beer's law, this paper introduces the influence of porosity on electron diffusion coefficient into the mathematical model of DSSC using constant stacking method and variable stacking method, and establishes a more comprehensive and accurate electron transfer model. This model can deeply analyze the impact of changes in the structure parameters of the photoanode on the performance of DSSC. The performance of DSSC under different pore volumes, electron lifetime, SnO2 coating thickness, and specific surface area were simulated through numerical simulation. The results show that as the pore volume of SnO2 thin films increases, the short-circuit current density of solar cells gradually decreases, while the open circuit voltage shows an increasing trend, leading to a gradual decrease in photoelectric conversion efficiency. When the pore volume reaches 0. 10 cm3 / g, its photoelectric conversion efficiency reaches 5. 16%. Therefore, while ensuring the rigidity of the battery, reducing the pore volume of SnO2 as much as possible is beneficial for improving the absorption coefficient and diffusion coefficient. The improvement of these two parameters is conducive to the overall performance of DSSC. At the same time, the extension of electron lifetime will bring about an increase in the short-circuit current density and open circuit voltage of solar cells, thereby improving the photoelectric conversion efficiency. When the electron lifetime reaches 200 ms, its photoelectric conversion efficiency reaches 5.82%. This study provides strong theoretical guidance for optimizing the photoanode structure and improving the photoelectric performance of DSSC through detailed numerical simulation analysis, which helps to further promote the research and application of dye sensitized solar cells. [ABSTRACT FROM AUTHOR]

Umifenovir, an antiviral drug that is used to treat influenza, has recently been used in regards to COVID-19 infection. According to a literature survey, no UV technique for the estimation of umifenovir has yet been established; hence, there is an imperative need for a simple analytical method. Additionally, we developed an alternative reverse-phase high-performance liquid chromatography (RP-HPLC) method for the estimation of umifenovir. UV spectrophotometry was carried out at 223 nm absorption maxima using the solvent methanol. A concentration range of 2–12 μg/mL was found to obey Beer's law, with a correlation coefficient (r2) of 0.9995. A C-18 column (250 mm, 4.6 μm, 5 μm) was used for chromatographic separation using the isocratic mode. The mixture consisted of acetonitrile: 0.1% trimethylamine (pH adjusted to 2.7 by the addition of orthophosphoric acid) 60:40 as the mobile phase with a flow rate of 1 mL/min. The temperature was kept at 25°C, and detection at 223 nm was performed using a PDA detector. The estimated percentage of the drug was close to 100%, corresponding to the label claim of the tablet made in the laboratory. The results and statistical study demonstrated the utility of the current methods in the routine evaluation of umifenovir bulk and formulation. [ABSTRACT FROM AUTHOR]

Significance: Diffuse optical modalities such as broadband near-infrared spectroscopy (bNIRS) and hyperspectral imaging (HSI) represent a promising alternative for low-cost, non-invasive, and fast monitoring of living tissue. Particularly, the possibility of extracting the molecular composition of the tissue from the optical spectra deems the spectroscopy techniques as a unique diagnostic tool. Aim: No established method exists to streamline the inference of the biochemical composition from the optical spectrum for real-time applications such as surgical monitoring. We analyze a machine learning technique for inference of changes in the molecular composition of brain tissue. Approach: We propose modifications to the existing learnable methodology based on the Beer-Lambert law. We evaluate the method's applicability to linear and nonlinear formulations of this physical law. The approach is tested on data obtained from the bNIRS- and HSI-based monitoring of brain tissue. Results: The results demonstrate that the proposed method enables real-time molecular composition inference while maintaining the accuracy of traditional methods. Preliminary findings show that Beer-Lambert law-based spectral unmixing allows contrasting brain anatomy semantics such as the vessel tree and tumor area. Conclusion: We present a data-driven technique for inferring molecular composition change from diffuse spectroscopy of brain tissue, potentially enabling intraoperative monitoring. [ABSTRACT FROM AUTHOR]

Novel and sensitive analytical technique was proposed for estimating perindopril (angiotensin-converting enzyme (ACE) inhibitor) in formulations using acidic dye as chromogenic reagent. The study was established on the development of colour species formation between perindopril erbumine and chromogenic reagent such as azocarmine G (ACG). Proposed method consists formation of an ion-pair association complex with azocarmine-G. The optical density was measured at λmax of 540 nm. Regression analysis of proposed method showed that the linearity lies within the concentration limits of 20-100 µg mL-1. Molar absorptivity (∈max) values of developed method are found to be as 3.22 x 10Á L mol-1 cm-1. Investigated method was found to have linear correlation coefficient (r) value of 0.9999. Proposed method obeyed Lambert-Beer' law with reproducible results. Percentage recovery was found to be within the limits of 99.7 - 100.1 (± 0.41 SD, ± 0.57 SD). All the parameters were validated statistically. [ABSTRACT FROM AUTHOR]

This paper presents an innovative approach integrating the Image Processing Method and the Beer-Lambert Law to study Sea Water Intrusion in riverine systems. Using an experimental setup, this study characterizes the dynamics between saline and fresh waters, providing detailed spatial and temporal salinity distribution analyses. The Beer-Lambert Law using Python is employed to convert image pixel data to accurate concentration measurements, essential for understanding the diffusion and mixing processes of saline wedges. Results showed that the concentration of the salt water is decreased when it flows upstream horizontally. also, the concentration of the saline water is decreased vertically, due to the salt and fresh water mixing. The "Max Concentration Profile" graph shows a sharp peak at the start, reaching approximately 1000 g/cm³, marking the point of saline introduction. Within the first 10 cm, the concentration rapidly decreases to about 600 g/cm³, indicating swift diffusion and dilution. Beyond this point, the concentration gradually decreases, stabilizing around 200 g/cm³ past the 100 cm mark, reflecting ongoing diffusion and mixing processes. The "Concentration Contour" graph shows high salinity concentrations near the bottom 10 cm of the flume. Salinity concentration decreases moving vertically up the flume, indicated by cooler colors. From approximately 30 cm in height, salinity remains low and uniform, suggesting that denser saline water settles at the bottom due to gravity.

Due to the lack of other treatment options, a rebirth of polymyxins is urgently required. Colistin (also called polymyxin E) and polymyxin B are the only two examples of this antibiotic class that were effectively employed in such critical situations. In the present work, both of the two studied medications were quantified via a simple, green, and non-extracting spectrophotometric approach based on the formation of ion-pair complexes with Erythrosine B. Without using any organic solvents, the pink color of the created complexes was detected at wavelength = 558 nm. To achieve the highest intensity of absorbance, optimum conditions were established by the screening of many experimental factors such as pH, buffer volume, the volume of Erythrosine B, and the time consumed to undergo the reaction. For Colistin and Polymyxin B respectively, Beer-Lambert's law was observed at the concentration ranges of 1–6, 1–9 µg mL− 1. The technique was approved and validated following ICH recommendations. Lastly, the suggested approach has been successfully implemented to quantify the cited medications colorimetrically, for the first time, in their parenteral dosage forms with excellent recoveries. Also, Content uniformity testing was implemented. [ABSTRACT FROM AUTHOR]

Leaf area index (LAI) is a vital input variable for crop growth and yield prediction models. Therefore, rapid and accurate crop LAI estimates can offer important information for monitoring and managing the quantity and quality of food production. Here, LAI values of maize and soybean were predicted applying height metrics and intensity metrics calculated through unmanned aerial vehicle (UAV) LiDAR data. Moreover, we compared the prediction performance of physical model with that of empirical model for estimating crop LAI. The physical model based on Beer–Lambert law yielded reliable estimation results using LiDAR height data (maize: R2 = 0.815, RMSE = 0.385; soybean: R2 = 0.627, RMSE = 0.515) and LiDAR intensity data (maize: R2 = 0.719, RMSE = 0.474; soybean: R2 = 0.548, RMSE = 0.567). However, the linear regression model obtained a higher estimation accuracy. The single linear regression model derived from LiDAR height data had an R2 value of 0.837 (RMSE = 0.361) for maize and 0.658 (RMSE = 0.493) for soybean, and derived from LiDAR intensity data had an R2 value of 0.749 (RMSE = 0.448) for maize and 0.460 (RMSE = 0.619) for soybean, respectively. We found that the random forest (RF) regression model yielded the lowest estimation accuracy in this study. Moreover, the RF regression model in our study was not able to reliably estimate soybean LAI whether using LiDAR height metrics (R2 = 0.294) or intensity metrics (R2 = 0.180). Our results show that both LiDAR intensity and height metrics are capable of reliably predicting maize and soybean LAIs, although LiDAR intensity data yielded lower estimation accuracy than LiDAR height data. In conclusion, the results presented in this study demonstrate that using UAV-LiDAR technology to predict crop LAI is a flexible, practical, and cost-effective method. [ABSTRACT FROM AUTHOR]

A novel reagent derived from salicylaldehyde has been synthesized and characterized by determining its crystalline structure through X-ray diffraction analysis. The complex formation of this reagent with iron(III) has been investigated by spectrophotometric methods. The dissociation constant of the reagent was determined by potentiometry in an aqueous–ethanolic medium, yielding pK = 9.66 ± 0.02. The interaction of iron(III) with 2-(((1-(3-bromophenyl)ethylidene)hydrazono)methyl)phenol in the presence and absence of diantipyrylmethane (DAM), diantipyrylphenylmethane (DAPhM), and diantipyrylpropylmethane (DAPrM) has been thoroughly studied. Optimal conditions for complex formation (λopt, pHopt) were found. Iron(III) forms colored mixed-ligand complexes with the reagent in the presence of the third component—DAM, DAPhM, or DAPrM,—resulting in a hypsochromic shift in the absorption spectrum. The maximum yield of complexes was achieved in a more acidic medium compared to the binary complex. Molar absorption coefficients of the complexes and the ranges of compliance with Beer's law were determined. Component ratios in the homogeneous and mixed-ligand complexes were established using isomolar series methods, as well as the relative yield of the Starik–Barbanel and equilibrium shift methods. These analyses revealed that the component ratio of Fe(III)–R in the binary complex is 1 : 2, while in the mixed-ligand complexes Fe(III)–R–DAM, Fe(III)–R–DAPhM, and Fe(III)–R–DAPrM, the ratios are 1 : 2 : 1, 1 : 1 : 1, and 1 : 1 : 2, respectively. The mixed-ligand complexes of iron(III) with 2-(((1-(3-bromophenyl)ethylidene)hydrazono)methyl)phenol exhibit favorable chemical-analytical characteristics. The developed procedure was successfully applied to the determination of trace amounts of iron(III) in oil sludge. [ABSTRACT FROM AUTHOR]

Purpose: The Beer–Lambert law suggests that visual pigment optical density (OD) should be linearly related to the length of photoreceptor outer segments (POSs). Mammalian studies indicate that visual pigment concentration increases with POS length, but the nature of this relationship may vary due to factors such as visual pigment packing density or retinal eccentricity, and may not necessarily be linearly related. The purpose of this study was to establish the relationship between OD and POS length in humans. Methods: Spectral domain optical coherence tomography (OCT) was used to image POS, and imaging retinal densitometry (IRD) was used to measure OD at corresponding locations in 19 healthy participants (age range 25–82 years). POS length and OD measurements were extracted from OCT and IRD images at 23 discrete locations spanning the central 9° of the retina. The averaged data from all participants were fitted with models based on the Beer–Lambert law to establish the relationship between OD and POS length. Results: Visual pigment OD increased monotonically with POS length, but the relationship was non‐linear, and a straight‐line fit, based on a simple interpretation of the Beer–Lambert law, provided a poor description. A model allowing for different rod and cone visual pigment concentrations provided a superior fit. Specifically, the data were well described by a model where the molar concentration of visual pigment in cones and rods were 3.8 × 10−3 mol/L and 1.8 × 10−3mol/L, respectively. Conclusions: In accordance with the Beer–Lambert law, the results indicate that OD increases monotonically with POS length in humans, but the precise relationship is dependent on photoreceptor type. These results suggest that visual pigment concentration in rods is only about 48% of that found in cones. This may be due to the ubiquitous nature of artificial light that works to reduce the concentration of rhodopsin in rod photoreceptors. [ABSTRACT FROM AUTHOR]

Background Galidesivir hydrochloride (GDV) is a new potent and safe antiviral drug used for the treatment of a broad spectrum of viral diseases, including COVID-19. In the literature, no analytical method exists for the determination of GDV in bulk or dosage form. Objective The objective of this study was the investigation of oxidation reactions of GDV with five inorganic oxidizing reagents and the employment of the reactions in the development of five green microwell spectrophotometric methods (MW-SPMs) with simple procedure and high throughputs for determination of GDV in its bulk and dosage forms (capsules). Methods The reactions were carried out in 96-well plates, and the absorbances of reaction solutions were measured by an absorbance microplate reader. Variables influencing the reactions were carefully investigated and optimized. Results Under the refined optimum conditions, Beer's law with excellent correlation coefficients (0.9992–0.9997) was followed in GDV concentrations in a general range of 5–700 µg/mL, and the limits of detection were ≥1.8 µg/mL. All validation parameters of all methods were acceptable. The methods were successfully applied to the analysis of GDV in bulk drug and capsules with high accuracy and precision; the recovery percentages were 98.6–101.2 ± 0.58–1.14%. The greenness of MW-SPMs was evaluated by three comprehensive metric tools, which demonstrated the adherence of MW-SPMs to the principles of the green analytical chemistry (GAC) approach. Conclusions The proposed MW-SPMs combined the advantages of microwell-based practice and the use of common laboratory reagents for the analysis. The advantages of microwell analysis were the high throughput, readily available for semi-automation, reduced samples/reagents volume, precise measurements, and versatility. The advantages of using common laboratory reagents were the availability, consistency, compatibility, safety, and cost-effectiveness. Highlights Overall, the proposed MW-SPMs are versatile, valuable tools for the quantitation of GDV during its pharmaceutical manufacturing. [ABSTRACT FROM AUTHOR]

Mole fraction solubilities have been experimentally determined for 2,3-dimethoxybenzoic acid dissolved in propanenitrile and diisopropyl ether, in two more alkyl alkanoates (tert-butyl acetate, methyl butanoate), and in ten more alcohols (1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 2-methyl-1-propanol, 2-butanol, 2-pentanol, 3-methyl-1-butanol, 4-methyl-2-pentanol, cyclopentanol) at 298.15 K using a spectrophotometric method of chemical analysis based on the Beer-Lambert law. Experiment-based solute descriptors for the monomeric form of the dissolved carboxylic acid solute have been calculated using the results from our solubility measurements, combined with published solubility data taken from the chemical literature. The calculated solute descriptors provide a reasonably accurate mathematical description of the observed solubility data, with the overall standard deviation between the observed and back-calculated values being 0.074 log units. The solute descriptors further suggest that the carboxylic acid solute does not undergo intramolecular hydrogen bonding in the 28 organic solvents considered in the current study. [ABSTRACT FROM AUTHOR]

A simple, sensitive, and rapid spectrophotometric method for the determination of Cu(II), Ni(II), Co(II), and Mn(II) ions is proposed based on the complexation of metal ions with a synthesized ligand, 4-methylpiperazine dithiocarbamic acid, formed by the reaction of 4-methyl piperazine and carbon disulfide under cold conditions. The colored complex formed by the reaction of the synthesized ligand with these heavy metals in an aqueous acetonitrile medium exhibits absorbance maxima at 435, 395, 370, and 495 nm for Cu, Ni, Co, and Mn metals, respectively. Beer's law was valid within concentration ranges of 0.34–20.46, 0.49–39.81, 0.47–38.07, and 0.49–11.03 µg/mL for Cu, Ni, Co, and Mn, respectively. Various reaction parameters such as pH, volume of reagent, and solvents were carefully studied and optimized. The limits of detection and limits of quantification for Cu, Ni, Co, and Mn were found to be 1.4, 2.4, 1.1, and 1.1 µg/mL and 4.2, 7.2, 3.3, and 3.3 µg/mL, respectively. The method proved to be sensitive and rapid, requiring only a few minutes for sample analysis. The synthesized ligand and metal(II) 4-methyl piperazine dithiocarbamate complexes, M(4-methylPzdtc)2, were characterized by FTIR. The method was subsequently applied to vegetable and water samples spiked with the cations. The high recoveries of Cu, Ni, Co, and Mn from the proposed method indicate good accuracy and precision. [ABSTRACT FROM AUTHOR]

Quantitative extraction of the Pd(II) complex with 5-Chlorosalicylaldehyde thiosemicarbazone (CSTSC) was achieved at pH levels ranging from 3.6 to 4.4 after a 30-second equilibration period in n-butyl acetate. When the concentration of Pd(II) does not exceed 9.0 µg mL-1, the complex formed between Pd(II) and 5-Chlorosalicylaldehyde thiosemicarbazone complies with Beer's law, and it displays the highest absorbance at 400 nm. By means of the mole ratio method and the Jobs continuous variation method, it was determined that the stoichiometry of the Pd(II)-CSTSC complex is 1:2. The stability of the extracted complex persisted for 96 hours. The calculated Sandell's sensitivity was 9.92 x 10-3 µg cm-2, while the molar absorptivity was found to be 1.072 x 104 L mol-1 cm-1. Utilizing this method, effective analysis has been carried out on synthetic samples, complexes, and water samples. [ABSTRACT FROM AUTHOR]

Hemolytic activity assessment is a widely used method to evaluate the toxicity of marine organisms, including jellyfish. However, there are some challenges associated with testing hemolytic activity. In this study, four methods were employed to compare the hemolytic activity of jellyfish tentacle extract (TE). Firstly, a microplate reader was used to compare the mouse hemoglobin solution at three different wavelengths (415 nm, 541 nm, and 576 nm), and the most sensitive wavelength was selected for further experiments. Secondly, photomicrograph counting was used to determine the number of complete red blood cells in the field of view. Thirdly, a microplate reader was used to test hemolytic activity in a 96-well plate at 415 nm. Fourthly, a Bicinchoninic Acid (BCA) kit was used to test the concentration of hemoglobin in the solution. Finally, a UV-Vis Spectrophotometer was used to test hemolytic activity at 415 nm. Among the three wavelengths tested, the absorption value was most sensitive at 415 nm. The photomicrograph counting method was able to reflect changes in the shape of Red Blood Cells (RBCs). The microplate reader method may exhibit deviations when the solution concentration is high, while external factors could influence the BCA kit when the toxin concentration in the experimental group is low. The spectrophotometer method was found to be relatively accurate and sensitive to changes. When optimizing the method, it is important to consider the applicability of the Beer-Lambert law and the concentration of solutions. [ABSTRACT FROM AUTHOR]

For the determination of tin(II) traces, an extractive spectrophotometric approach is devised. The applied method serves a powerful tool for determination of tin(II), involves the formation of yellow colored complex after the binding of 6-bromo-3-hydroxy-2-(5-methylfuran-2-yl)-4H-chromen-4-one (BHMF) and tin(II) in 1:2 stiochiometry in a slightly acidic medium (HCl). The complex shows absorbance at 434 nm with respect of the blank reagent. The outcomes of spectral investigation for complexation showed a Beer's range of 0–1.3 μg Sn mL−1, molar absorptivity, specific absorptivity and Sandell's complex sensitivity are 9.291 × 104 L mol−1 cm−1, 0.490 mL g−1 cm−1 and 0.002040 μg cm−2 at 434 nm that was stable for two days. The interferences study results showed that this method is free from interferences, when tested with metal ions including Ag, Be, Bi, Ca, Cd, Ce, Co, Hg, Mo, Re, Pt, Se,Ti, U, V, W and other common cations, anions, and complexing agents. The applied method is quite simple, highly selective, and sensitive with good re-producibility. This method has been satisfactorily by utilizing the proposed procedure, and its applicability has been tested by analyzing synthetic samples and an alloy sample of gunmetal. The procedure assumes this because of the scarcity of better methods for determining tin(II). The results are in good agreement with the certified value. [ABSTRACT FROM AUTHOR]

UV Spectrophotometric method has been developed to determine Gliclazide in bulk pure and tablet forms. It is a simple, accurate, reproducible, rapid and less time-consuming method. The maximum wavelength of the drug was found to be 232nm. Beer Lamberts' law was obeyed in the concentration range of 2-20 µg/ml. (LOD)The limit of detection and limit of qualification (LOQ) was found to be 0.16 µg/ml and 0.50 µg/ml from this method per cent recovery of the drug was found to be 99.30% which indicates no interaction of the excipients. This method was found accurate, simple, precise and rapid for determination of tablet dosage form. [ABSTRACT FROM AUTHOR]

Introduction: The Salkowski reagent method is a colorimetric technique used to determine auxin production, specifically as indole-3-acetic acid (IAA). It was developed to determine indoles rapidly; however, it does not follow Beer's law at high concentrations of IAA. Thus, there could be an overestimation of IAA with the Salkowski technique due to the detection of other indole compounds. Methods: This study aims to compare the Salkowski colorimetric method versus a chromatographic method to evidence the imprecision or overestimation obtained when auxins, such as indole-acetic acid (IAA), are determined as traits from promoting growth plant bacteria (PGPB), using ten different strains from three different isolation sources. The analysis used the same bacterial culture to compare the Salkowski colorimetric and chromatographic results. Each bacterium was cultivated in the modified TSA without or with tryptophan for 96 h. The same supernatant culture was used in both methods: Salkowski reagent and ultra-performance liquid chromatography coupled with a Mass Spectrometer (LC-MS/MS). Results: The first method indicated 5.4 to 27.4 mg L-1 without tryptophan in ten evaluated strains. When tryptophan was used as an inductor of auxin production, an increase was observed with an interval from 4.4 to 160 mg L-1. The principal auxin produced by all strains was IAA from that evaluated by the LC-MS/MS method, with significantly higher concentration with tryptophan addition than without. Strains belonging to the Kocuria genus were highlighted by high IAA production. The indole-3-propionic acid (IPA) was detected in all the bacterial cultures without tryptophan and only in K. turfanensis As05 with tryptophan, while it was not detected in other strains. In addition, indole-3-butyric acid (IBA) was detected at trace levels (13-16 µg L-1). Conclusions: The Salkowski reagent overestimates the IAA concentration with an interval of 41-1042 folds without tryptophan and 7-16330 folds with tryptophan as inductor. In future works, it will be necessary to determine IAA or other auxins using more suitable sensitive techniques and methodologies. [ABSTRACT FROM AUTHOR]

Three methods are used for a numerical solution, the Monte Carlo method, diffusion approximation equation model, and beam broaden model based on Beer-Lambert's law equation. The comparison between the first two methods is reported theoretically, and the latter is a better choice in the high-density tissue. However, the comparison between the third method and the first or the second method is rarely reported. Two classical theoretical models describing the interaction between the laser and the bio-tissue are analyzed and compared to determine which is more suitable for analyzing the interaction, the beam broaden model or diffusion approximation equation model. Intensity distribution is simulated and compared for the two models. Temperature distribution and thermal damage are investigated theoretically and experimentally for both models. The differences and the reasons are analyzed. The diffusion approximation equation model is more suitable for analyzing the mechanism between the laser and the bio-tissue based on the degree of fitting between the simulated and experimental data. Theoretical analyses for the two models are carried out in detail. The comparison between the two models is rarely reported, and it is reported in this article for the first time, theoretically and experimentally. This report provides a better choice for quickly analyzing the interaction mechanism between the laser and the bio-tissue. [ABSTRACT FROM AUTHOR]

Significance: Pulse oximetry is a well-established technique for the assessment of arterial oxygen Saturation (SaO2). A quantitative analysis of its basic measurements may benefit its further development. Aim: We aim to derive and discuss the quantitative relationship between SaO2 and the measured quantity in pulse oximetry and the ratio-of-ratios (R) of pulsatile intensities at red and infrared wavelengths. Approach: The source of the pulsatile optical signal is the systolic and diastolic pulsation of the arterial compartment within the probed tissue. From a diffuse optics point of view, this is associated with an absorption change in the region that arterial blood expands into and a mean partial optical path length through that expanded arterial volume. This observation is the basis for a modified Beer-Lambert law analysis of the relationship between SaO2 and R. Results: The equation that relates SaO2 and R contains parameters that include the molar extinction coefficients of oxy- and deoxy-hemoglobin and the ratio of the mean partial optical path lengths in the arterial pulsatile expansion volume at the two wavelengths. Conclusion: The analysis reported here clarifies the source of the calibration equations used in pulse oximetry and provides guidance to assess the impact of various key optical parameters on the accuracy of pulse oximetry. [ABSTRACT FROM AUTHOR]

A spectrophotometric method has been developed for the determination of certain amine-phenol-containing drugs, namely, adrenaline, phenylephrine hydrochloride, and terbutaline sulfate. The method depends on the formation of new products by the reaction of drugs with the Gibbs reagent (2,6-dichloroquinone-4-chloroamide) in a basic borate buffer medium with a pH value of 11. The products were measured at 475, 652.5, and 547 nm for the aforementioned drugs, respectively. Beer–Lambert law was obeyed in the ranges of 0.3–9.5, 0.5–17, and 0.5–55 µg/mL with average recovery of 101.10, 99.13, and 99.78% and a relative standard deviation of ≤3.31%, respectively. The method was free from excipient interferences and applied successfully for the assay of the studied drugs in their pharmaceutical formulations. The resulting products were found in the ratio of 1 : 1. [ABSTRACT FROM AUTHOR]

The article introduces the BrickPhotometer, a low-cost spectrophotometer designed for use in secondary school chemistry education. The device, made of building blocks and a smartphone, allows for the measurement of visible light spectra by capturing digital images and reading gray values. While there are limitations in accuracy, the BrickPhotometer can still be used for qualitative and quantitative analysis of spectra, making it a valuable tool for teaching spectrophotometry in the classroom. The authors suggest potential experiments that can be conducted using the device, such as determining water trophic state or studying reaction kinetics. [Extracted from the article]