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Development of a Terbium-Sensitized Fluorescence Method for Analysis of Silibinin
摘要： Silibinin is a natural flavonoid with potent anticancer properties, as shown in both in vitro and in vivo experiments. Various methods have been used for silibinin analysis. Terbium-sensitized fluorescence methods have been widely used for the determination of drugs in pharmaceutical preparations and biological samples in recent years. The present work is aimed at providing a simple analytical method for the quantitative determination of silibinin in aqueous solutions based on the formation of a fluorescent complex with terbium ion. Terbium concentration, pH, and volume of buffer, the important effective parameters for the determination of silibinin by the proposed method, were optimized using response surface methodology. The fluorescence intensity of silibinin was measured at 545 nm using λex = 334 nm. The developed method was applied for the determination of silibinin in plasma samples after protein precipitation with acetone. Under optimum conditions, the method provided a linear range between 0.10 and 0.50 mg/L, with a coefficient of determination (R2) of 0.997. The LOD and LOQ were 0.034 and 0.112 mg/L, respectively. These results indicate that the developed method is a simple, low-cost, and suitable analytical method for the quantification of silibinin in aqueous solution and plasma samples.
关键词： Response surface methodology,Plasma samples,Quantitative determination,Silibinin,Terbium-sensitized fluorescence
更新于2025-09-23 15:21:01
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Optical Chirality Sensing with an Auxiliary-free Earth-abundant Cobalt Probe
摘要： Broadly useful chiroptical ee sensing remains challenging and typically involves carefully designed molecular receptors or supramolecular assemblies. Herein, we describe enantioselective sensing of 35 amino acids, amino phosphonic acids, hydroxy acids, amino alcohols and diamines with an auxiliary-free cobalt probe. Chiroptical analysis of the enantiomeric composition and concentration of minute sample amounts is achieved with high accuracy using earth-abundant cobalt salts and hydrogen peroxide as oxidant. Despite the absence of an auxiliary ligand, the cobalt assay is applicable to aromatic and aliphatic compounds and yields strong CD signals at high wavelengths. This method eliminates the general prerequisite for chromophoric metal ligands to generate chiroptical signals via ECCD effects or through analyte-to-ligand chirality induction, and it offers operational simplicity, cost-efficiency, waste reduction and speed.
关键词： ee determination,concentration analysis,Werner complexes,Chirality sensing,chiroptical spectroscopy
更新于2025-09-23 15:21:01
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[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Investigation of 100 GHz Output Power Performance in Uni-travelling Carrier Photodetector under Zero-bias Condition
摘要： This study is concerned with a design of membership functions of fuzzy sets. The membership functions are formed in such a way that they are experimentally justifiable and exhibit a sound semantics. These two requirements are articulated through the principle of justifiable granularity. The parametric version of the principle is discussed in detail. We show linkages with type-2 fuzzy sets, which are constructed on a basis of type-1 fuzzy sets. Several experimental studies are reported, which illustrate a behavior of the introduced method.
关键词： type-2 fuzzy set,interval-valued fuzzy set,principle of justifiable granularity,membership function determination,Coverage of data,specificity
更新于2025-09-23 15:19:57
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Determination of the isotopic composition of enriched materials using laser ablation molecular isotopic spectrometry: partial least squares and multivariate curve resolution for the determination of 15N content in enriched urea
摘要： A quantitative analytical method based on laser ablation molecular isotopic spectrometry (LAMIS) and multivariate analysis was developed and evaluated for the determination of the isotopic composition of enriched materials. The method consists preparing a concentrated solution of the enriched material, using small quantities of a sample (125 mg), and ensuring the economic efficiency of the analysis. Standard solutions of known isotopic contents are prepared by employing mixtures of urea highly enriched in 15N and urea of natural isotopic ratio and analyzed by mass spectrometry. A small volume (30 μL) of these solutions is delivered to a filter paper disc (3 cm diameter). After drying, the disc, offering a homogeneously distributed analyte, is presented to a LAMIS equipment to acquire the vibronic emission spectra containing information about the isotopologues of interest. To illustrate the proposed method, the content of 15N is determined in enriched samples of urea. In this case, each spectrum is normalized by the intensity of emission of the CN isotopologues for the electronic (Δν = 0) emission band at 387.1 nm, ensuring better accuracy. Selected regions and single wavelengths of the vibronic emission spectrum (Δν = + 1 or ? 1) related to CN species were employed to construct multivariate partial least squares (PLS) and univariate regression models to predict the isotopic content of new samples. Besides, the LAMIS data set was evaluated by multivariate curve resolution (MCR) algorithm. The best MCR and PLS models presented similar results regarding the accuracy to determine 15N content in enriched urea. MCR is capable of identifying spectral interferences and minimizing its effect. The results show that the proposed method based on LAMIS and PLS or MCR multivariate analysis can determine the 15N content in the range 5–50% with a root mean square error of prediction (RMSEP) respectively equal to 0.5 or 0.7% (m/m) in comparison with reference results obtained by mass spectrometry.
关键词： 15N determination in enriched urea,Laser ablation molecular isotopic spectrometry (LAMIS),Isotopic composition of enriched materials,Partial least squares,Multivariate regression,Multivariate curve resolution (MCR)
更新于2025-09-23 15:19:57
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Neon plasma for effective ionisation of oxygen and fluorine in pulsed glow discharge – high ionisation energy elements quantification in potassium titanyl phosphate single crystals
摘要： Neon glow discharge was tested for the direct analysis of solid dielectric materials by pulsed glow discharge time-of-flight mass spectrometry with an emphasis on the elements with high ionisation energy. The findings for neon were compared to conventional argon glow discharge. Fluorine doped potassium titanyl phosphate (KTP) single crystals were used for analysis. The following parameters were optimised: repelling pulse delay, discharge duration and voltage and pressure in the discharge cell. Relative sensitivity factors were used for quantification; titanium was used for normalisation. Similar to argon glow discharge, the most effective mechanism for fluorine and oxygen ionisation was found to be attributed to high-energy electrons under short repelling pulse delays. Penning ionisation of oxygen in neon glow discharge was found to be less efficient. Overall, the use of neon significantly benefited fluorine and oxygen determination; the limits of detection for oxygen (0.0005 mass %) and fluorine (0.0002 mass %) decreased several times compared to argon glow discharge (0.001 and 0.01 mass %, respectively) as a result of more effective ionisation. The improvement was especially pronounced for fluorine, due to the alleviation of plasma-based interferences. However, for other KTP constituents – potassium, phosphorus and titanium – the analytical performance was expectedly lower, due to the lower sputtering rates in neon glow discharge. The limits of detection for potassium and phosphorus were significantly increased, being 0.008 mass % and 0.01 mass %, respectively. Notably, the performance for non-high ionisation energy elements was adequate for their single-run quantification along with oxygen and fluorine at non-trace levels. Thus, the use of neon as discharge medium for pulsed glow discharge mass spectrometry is clearly justified for the determination of high ionisation energy elements such as oxygen and fluorine in non-conducting matrices.
关键词： oxygen,mass spectrometry,neon,direct determination,fluorine,pulsed glow discharge
更新于2025-09-19 17:15:36
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Photoreceptor Fate Determination in the Vertebrate Retina
摘要： Photoreceptors are highly specialized primary sensory neurons that sense light and initiate vision. This critical role is well demonstrated by the fact that visual impairment accompanies photoreceptor loss or dysfunction in many human diseases. With the remarkable advances in stem cell research, one therapeutic approach is to use stem cells to generate photoreceptors and then engraft them into diseased eyes. Knowledge of the molecular mechanisms that control photoreceptor genesis during normal development can greatly aid in the production of photoreceptor cells for this approach. This article will discuss advances in our understanding of the molecular mechanisms that regulate photoreceptor fate determination during development. Recent lineage studies have shown that there are distinct retinal progenitor cells (RPCs) that produce specific combinations of daughter cell types, including photoreceptors and other types of retinal cells. Gene regulatory networks, in which transcription factors interact via cis-regulatory DNA elements, have been discovered that operate within distinct RPCs, and/or newly postmitotic cells, to direct the choice of photoreceptor fate.
关键词： retinal development,photoreceptor fate determination,transcription factors,gene regulatory network,cell lineages
更新于2025-09-19 17:15:36
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Detection/quantification of amyloid aggregation in solution using the novel fluorescent benzofuranone-derivative compounds as amyloid fluorescent probes: synthesis and in vitro characterization
摘要： Neurodegenerative diseases are characterized by the presence of amyloid deposition. Thioflavin T (ThT) has been one of the molecules of choice to attempt the detection of the amyloid deposits, but ThT is unable to cross blood–brain barrier, due to its low lipophilicity. Therefore, there is strong motivation to design and develop new compounds for in vitro fibril detection as well as for in vivo amyloid imaging. Additionally, the importance and critical role of oxidative stress in the onset/progression of some neurodegenerative disorders, and therefore, the efficacy of aurone compounds in inhibiting the resulting toxicity have been frequently reported. In this study, we report the synthesis of some benzofuranone compounds and examine their antioxidant inhibitory property. Furthermore, to establish the potential detection of synthesized compounds to amyloid aggregates, their in vitro binding to some non-disease related amyloidogenic proteins were characterized. Analyses of the in vitro binding studies showed that compounds 3 and 4 bind to the fibril structures successfully while compounds 1, 2 and 5 indicated a low affinity binding to amyloid. Additionally, compounds 3 and 4 exhibited very good antioxidant properties. Furthermore, these compounds have a great potential as fluorescent probes for detecting amyloid aggregation for further investigations.
关键词： BSA,β-Lactoglobulin,Antioxidant activity,Amyloid determination
更新于2025-09-19 17:15:36
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The convenient use of fluorescamine for spectrofluorimetric determination of midodrine hydrochloride in pure form and its tablets formulation: Application to content uniformity testing
摘要： A novel sensitive and simple spectrofluorimetric method was developed then validated for determination of midodrine in both its authentic pure form and its tablets. This method is based on the reaction between midodrine's aliphatic primary amine moiety with fluorescamine reagent, using borate buffer at pH 7.8 and yielding a highly fluorescent product whose fluorescence intensity was measured at 462 nm after excitation at 388 nm. This method represents the first attempt for determination of midodrine spectrofluorimetrically. A calibration curve was constructed showing that the linear range was 0.2–3.0 μg/ml. The limit of detection and limit of quantitation values were 0.06 and 0.19 μg/ml respectively. The correlation coefficient (r) and the determination coefficient (r2) values were 0.9992 and 0.9984 respectively. The proposed method was validated according to ICH guidelines and successfully applied for determination of midodrine in its tablets with an overall % recovery of 99.56 ± 0.95. Finally, the presented method was adapted to study the content uniformity test according to United States Pharmacopeia guidelines.
关键词： content uniformity testing,fluorescamine,midodrine hydrochloride,spectrofluorimetric determination
更新于2025-09-19 17:15:36
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Confidence Distance Matrix for outlier identification: A new method to improve the characterizations of surfaces measured by confocal microscopy
摘要： This paper proposes a statistical method for outlier identification for surface measurement data obtained by confocal microscopy. The implemented statistical method is Confidence Distance Matrix (CDM) which were widely used in statistics and many engineering areas, such as signal processing, sensor data fusion, information problems, etc. However, no investigations on identifying outliers in measured surface data using CDM have been found. This paper introduces and simplifies the mathematical model of CDM method. Algorithms for identifying random outliers using Monte Carlo method for uncertainty evaluation and for identifying outliers in a unique measured surface are developed and validated. For validation of the algorithms, a synthetic data SG_3-3 provided by National Institute of Standards and Technology and a data of artificial stochastic surface generated by our own algorithms are implemented. The difference of Sq of the data with outliers is 2.3342% and after deletion of outliers is 0.0037% with reference to the certified value. A type C1 spacing standard with dust dropped is measured and processed using CDM. The difference of Sa decreases from 29.65% to 3.52% after processing outliers with reference to the certified value Ra. An iron surface is measured and processed. Surface slopes and curvatures of the data in the two validations and two experiments are compared. All those parameters, the surface reconstructions, histogram of heights, and QQ plot of the measured surface data versus the data after deletion of outliers indicate our proposed method working well.
关键词： Confidence Distance matrix,outlier detection,areal surface characterization,threshold determination,Imaging Confocal Microscopy,Monte Carlo method
更新于2025-09-19 17:15:36
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A direct and safe method for plutonium determination using total reflection X-ray fluorescence spectrometry
摘要： A direct, simple and safe micro-analytical method for the determination of plutonium (Pu) using Total Reflection X-ray Fluorescence (TXRF) spectrometry is reported for the first time. The TXRF specimens were made by depositing sample solution aliquots containing 100–160 ng of Pu on quartz sample supports. The TXRF specimens of Pu, thus prepared after drying, were further isolated by dropcasting 10% collodion solution in amyl acetate on the sample spots. This novel methodology fixes Pu on TXRF supports, thus avoiding loose radioactive particles in TXRF specimens. These operations were carried out inside a fume hood. Since the analyte amount required for analysis was in ng levels, Pu particles fixed on the supports were in a non-dispersible form and the analysis was performed without touching the sample spot, there was no risk of Pu contamination, when these specimens were handled in the ambient atmosphere. The developed methodology showed the average precision of TXRF values as 3% (1s, n = 3) and the average deviation of TXRF determined values from the expected values was 6% with a sample size of 100–160 ng of Pu and measurement time of 2000 seconds. The detection limit for Pu was 0.4 ng. The studies resulted in the development of a TXRF compositional characterization method for precious, hazardous and radioactive samples without putting the instrument inside a glove box and thus, avoiding complicated handling of the spectrometer inside the glove box as well as minimizing the sample amount, radiation dose and the radioactive waste generation.
关键词： plutonium determination,TXRF spectrometry,micro-analytical method,radioactive samples,collodion isolation
更新于2025-09-19 17:15:36