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The Scopoletin-HRP Fluorimetric Determination of H2O2 in Seawaters—A Plea for the Two-Stage Protocol
摘要： A single solution protocol has been widely used for the ?uorimetric determination of H2O2 in natural waters by its bleaching of the ?uorescing scopoletin in the presence of the enzyme horseradish peroxidase (HRP). In this protocol, the reaction between scopoletin and H2O2 in the sample and the subsequent internal additions, and the measurements of the ?uorescence are all carried out at a single pH in a ?uorometer cell. It is found that this protocol is prone to four sources of possible error. The variability in the reaction stoichiometry between scopoletin and H2O2 in the presence of varying amounts of excess scopoletin, the effect of pH on the rate of reaction between scopoletin and H2O2, the photobleaching of scopoletin, and the de-activation of HRP. These possible sources of error can be circumvented in a two-stage protocol in which the reaction between H2O2 and scopoletin is carried out immediately upon sampling at a pH of 7, and the measurement of the ?uorescence is carried out later on at a pH of 9. It should be the protocol of choice. Furthermore, in the two-stage protocol, after the initial reaction between H2O2 and scopoletin, the sample may be stored at room temperature for six days and at 4 ?C for at least a month before its ?uorescence is measured. This option can signi?cantly reduce the logistics in the ?eld.
关键词： hydrogen peroxide,?uorimetric determination,horseradish peroxidase,scopoletin
更新于2025-09-09 09:28:46
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Fundamentals of Electroceramics (Materials, Devices, and Applications) || Elements of A Semiconductor
摘要： Semiconductor materials dominate modern electronics and microelectronics technology and have greatly influenced our civilization. Their impact is second to none in each and every aspect of our lives. There is hardly any device that we use in our daily life that has remained immune from the impact of semiconductors be it a child’s simple toy or a spaceship exploring the universe in quest of knowledge.
关键词： Semiconductor Properties,Energy Bands,Holes,n- and p-Type Conduction,Experimental Determination,Electrical Conduction,Semiconductor
更新于2025-09-09 09:28:46
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Precise determination of electron-affinity and band gap via optical response and optical spectra
摘要： In order to obtain both the band gap and a?nity of semiconductor by photoelectric e?ect and optical spectra, Lee A. DuBridge`s formula which describes the mathematical relationship between photocurrent and photon energy in metal is extended in semiconductor. Thus cut-o? energy of photon can be ?gured out via this formula, at the same time, the a?nity of semiconductor can be determined from the di?erence between cut-o? energy and band gap detected by optical spectra in semiconductor. The results of application on ?ve semiconductors prove that the method proposed in this paper is credible, the good agreements between experimental light energy-photoelectric yield curves and theoretical curves demonstrate that the classic Lee A. DuBridge`s theory of surface photoemission does an excellent job of ?tting the photo absorption pro?le shapes of semiconductor as an earlier application on metals, these results suggest that the Lee A. DuBridge`s formalism, which is straightforward and physical, may be of signi?cant utility in semiconductor spectroscopy. It is hoped also that the results will encourage a comprehensive theoretical analysis of the applicability of semiconductor. Beside, how the band gap of Cr3+ doped n-type TiO2 is controlled by composition of Ti is express with mathematical way.
关键词： Semiconductor,Determination,Band gap,Cut-o? energy,A?nity
更新于2025-09-09 09:28:46
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A green approach for the quantification of daptomycin in pharmaceutical formulation by UV spectrophotometry
摘要： Daptomycin is the first approved drug from a new class of antimicrobials, the cyclic lipopeptides, and is a very important antimicrobial agent in current clinical practice. Currently, there are no “green” analytical methods described in the literature to analyze the typical pharmaceutical dosage form of daptomycin. Thus, the aim of this work was to validate an environment-friendly spectrophotometric method in the UV region, for the analysis of daptomycin as a lyophilized powder. Water was used as diluent and the analyses were carried out on a spectrophotometer at 221 nm. The method met all validation requirements of the ICH guidelines, over a concentration range of 6-21 μg mL-1. A Student’s t-test demonstrated that the proposed method was comparable to an HPLC method previously validated. Thus, the validated spectrophotometric method could quantify daptomycin in a powder form for injectable solutions, while being an economical, rapid, and “green” alternative for routine analysis in quality control.
关键词： Antimicrobials/quality control,Daptomycin/determination,Spectrophotometry/green analytical method,Spectrophotometry/UV region/quantitative analysis
更新于2025-09-04 15:30:14
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Initial orbit determination using Doppler shift of Fraunhofer lines
摘要： Techniques for tracking objects in low Earth orbit include line-of-sight angle measurements and range measurements using RADAR or laser reflection. However, active ranging techniques are less effective for higher orbits because of the greater signal loss from distant targets. In this paper, using computer simulation, we show how incorporating measurements of the Doppler shift of Solar Fraunhofer lines can improve initial orbit determination. Results indicate that for Doppler measurement errors of less than 5 m/s, prediction accuracies for some orbital configurations can exceed Gooding’s angles-only method, while using only two observations of the target.
关键词： Space situational awareness (SSA),Fraunhofer lines,Initial orbit determination (IOD),Doppler shift
更新于2025-09-04 15:30:14
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Electrochromic effect of indium tin oxide in lithium iron phosphate battery cathodes for state of charge determination
摘要： In this paper, we discuss the origin of an optical effect in lithium iron phosphate (LFP) battery cathodes, which depends on the electrical charge transferred into the battery. Utilizing indium tin oxide (ITO) as an electrode additive, we were able to observe a change in reflectivity of the cathode during charging and discharging with lithiation and delithiation being clearly visible in the form of lithiation fronts. Further investigations using in situ video microscopy and in situ Raman spectroscopy on test cells with an optical window indicates that ITO additionally acts as an electrochromic marker within the LFP cathode. This enhances the optical effect due to local potentials around the lithiation fronts, which enables the voltage-dependent reflectivity of the ITO to be visible in the LFP cathode. Structural analysis with scanning electron microscopy (SEM) and X-ray crystallography (XRD) are presented as well. The observed effect allows for novel battery research methods and for a possible commercial application as a sensor for state of charge (SOC) estimation similar to the optical fiber approach reported by Ghannoum et al. for a graphite anode.
关键词： lithium ion batteries,battery state determination,lithium iron phosphate,raman spectroscopy,indium tin oxide,electrochromic marker,video microscopy,state of charge
更新于2025-09-04 15:30:14
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Development and validation of a simple spectrophotometric method for the determination of methyldopa in both bulk and marketed dosage formulations
摘要： A simple, precise, sensitive, rapid, specific and economical spectrophotometric method was developed to determine methyldopa (MTD) content in bulk and pharmaceutical dosage formulations. The proposed method was based on the formation of a colored product from the nitrosation reaction of MTD with sodium nitrite in an acid medium. The resultant nitroso derivative species reacts further with sodium hydroxide and is converted it into a more stable compound. This yellow nitrosation product exhibited an absorption maximum at 430 nm. Beer’s Law was obeyed in a concentration range of 6.37 to 82.81 mg mL-1 MTD with an excellent coefficient of determination (R2 = 0.9998). No interference was observed from common excipients in formulations. The results showed the method to be simple, accurate and readily applied for the determination of MTD in pure form and in pharmaceutical preparations. The analytical results obtained for these products using the proposed method are in agreement with those of the Brazilian Pharmacopoeia procedure at a 95% confidence level.
关键词： Pharmaceutical formulations/quality control,Spectrophotometry/qualitative analysis,Methyldopa/spectrophotometric determination
更新于2025-09-04 15:30:14
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Water-dispersed fluorescent silicon nanodots as probes for fluorometric determination of picric acid via energy transfer
摘要： Water-dispersed fluorescent silicon nanodots (SiNDs) were synthesized by a one-pot hydrothermal method starting from tetraethyl orthosilicate (TEOS) as silicon source and trisodium citrate as reducing reagent. The method is simple and convenient. The SiNDs, with excitation/emission peaks at 347/440 nm and with fluorescence quantum yield of 18% are shown to be viable fluorescent probes for picric acid (PA). The SiNDs strongly bind PA, and their blue fluorescence is quenched. The distance between the donor and acceptor (R0 value) is calculated from fluorescence data to be 2.1 nm. A fluorometric method was worked out that has a linear response in the 8 nM to 50 μM PA concentration range and a 0.92 nM limit of detection. The method has a fast response (2 min) and is well selective over other nitroaromatic compounds and metal ions. The average recoveries from spiked lake water samples ranged between 98.4 and 100.8%.
关键词： Nitroaromatic compounds,Picric acid (PA),Fluorometric determination,Tetraethyl orthosilicate (TEOS),Hydrothermal strategy
更新于2025-09-04 15:30:14