Understanding the behaviour of UV absorbance of natural waters upon chlorination using model compounds

2019 ◽  
Vol 5 (1) ◽  
pp. 172-184 ◽  
Author(s):  
Nicolas Beauchamp ◽  
Caetano Dorea ◽  
Christine Beaulieu ◽  
Christian Bouchard ◽  
Manuel Rodriguez
Keyword(s):  
Natural Waters ◽  
Uv Absorbance ◽  
Model Compounds ◽  
Chemical Structures ◽  
Uv Visible ◽  
By Products ◽  
Absorbance Spectra

This paper is the first to assess the chemical structures responsible for specific changes observed in the shape of the UV-visible absorbance spectra, and their relationship to disinfection by-products.

Quantitative UV Absorbance Spectra of Chemical Agents and Simulants

2008 ◽  
Author(s):  
J. M. Lochner ◽  
Aaron M. Hyre ◽  
Steven D. Christesen ◽  
Kristina R. Gonser
Keyword(s):  
Uv Absorbance ◽  
Chemical Agents ◽  
Absorbance Spectra

Growth of Ag Nanoparticles by Spin Coating

2013 ◽  
Vol 24 ◽  
pp. 163-167 ◽  
Author(s):  
S.D. Sartale ◽  
A.A. Ansari
Keyword(s):  
Ag Nanoparticles ◽  
Spin Coating ◽  
Chemical Reduction ◽  
Reduction Process ◽  
Thermal Reduction ◽  
Environment Effects ◽  
Uv Visible ◽  
Absorbance Spectra ◽  
Scanning Electron ◽  
Better Than

Ag nanoparticles were grown on glass substrate by spin coating of Ag ions (AgNO3) solution followed by either chemical reduction, in aqueous hydrazine or NaBH4 solution, or by thermal reduction in H2 environment. Effects of different reducing agent have been explained. Morphology and absorbance spectra ofAg nanoparticles films, measured by using Scanning Electron Microscopy (SEM) and UV-visible Spectrophotometer techniques, are used to understand effect of reduction process on growth of Ag nanoparticles. To grow uniformly size distributed Ag nanoparticles thermal reduction in H2 is better than chemical reduction by aqueous either NaBH4 orhydrazine hydrate solutions.

scholarly journals Effects of Cu-Doping on Optical Properties of NiO

2015 ◽  
Vol 48 ◽  
pp. 155-162 ◽  
Author(s):  
Nidhal Nissan Jandow
Keyword(s):  
Thin Film ◽  
Optical Properties ◽  
Absorption Coefficient ◽  
Extinction Coefficient ◽  
Energy Gap ◽  
Spray Pyrolysis Technique ◽  
Skin Depth ◽  
Cu Doping ◽  
Uv Visible ◽  
Absorbance Spectra

This work presents the effect of Cu-doping on some optical properties of Cu:NiO thin film prepared by spray pyrolysis technique. UV-Visible spectrophotometer in the range 380-900 nm used to determine the absorbance spectra for various Cu-doping of Cu:NiO thin film. The transmittance and energy gap are decreased with increasing Cu-doping in the prepared films, while absorption coefficient, extinction coefficient, and skin depth are increased with increasing Cu-doping.

scholarly journals Competitive cocrystallization and its application in the separation of flavonoids

IUCrJ ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 195-207
Author(s):  
Yanming Xia ◽  
Yuanfeng Wei ◽  
Hui Chen ◽  
Shuai Qian ◽  
Jianjun Zhang ◽  
...  
Keyword(s):  
Free Energy ◽  
Formation Constant ◽  
Energy Gap ◽  
Hirshfeld Surface ◽  
Methanol Solution ◽  
Model Compounds ◽  
Electronic Density ◽  
Chemical Structures ◽  
Similar Chemical ◽  
Interaction Contribution

Recently, cocrystallization has been widely employed to tailor physicochemical properties of drugs in the pharmaceutical field. In this study, cocrystallization was applied to separate natural compounds with similar structures. Three flavonoids [baicalein (BAI), quercetin (QUE) and myricetin (MYR)] were used as model compounds. The coformer caffeine (CAF) could form cocrystals with all three flavonoids, namely BAI–CAF (cocrystal 1), QUE–CAF (cocrystal 2) and MYR–CAF (cocrystal 3). After adding CAF to methanol solution containing MYR and QUE (or QUE and BAI), cocrystal 3 (or cocrystal 2) preferentially formed rather than cocrystal 2 (or cocrystal 1), indicating that flavonoid separation could be achieved by competitive cocrystallization. After co-mixing the slurry of two flavonoids with CAF followed by centrifugation, the resolution ratio that could be achieved was 70–80% with purity >90%. Among the three cocrystals, cocrystal 3 showed the lowest formation constant with a negative Gibbs free energy of nucleation and the highest energy gap. Hirshfeld surface analysis and density of states analysis found that cocrystal 3 had the highest strong interaction contribution and the closest electronic density, respectively, followed by cocrystal 2 and cocrystal 1, suggesting CAF could competitively form a cocrystal with MYR much more easily than QUE and BAI. Cocrystallization is a promising approach for green and effective separation of natural products with similar chemical structures.

scholarly journals Optical Method for Cardiovascular Risk Marker Uric Acid Removal Assessment during Dialysis

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Jana Holmar ◽  
Ivo Fridolin ◽  
Fredrik Uhlin ◽  
Kai Lauri ◽  
Merike Luman
Keyword(s):  
Uric Acid ◽  
Uv Absorbance ◽  
Chemical Laboratory ◽  
Dialysis Treatment ◽  
Mean Values ◽  
Double Beam ◽  
Multi Wavelength ◽  
Spent Dialysate ◽  
Treatment Procedures ◽  
Absorbance Spectra

The aim of this study was to estimate the concentration of uric acid (UA) optically by using the original and processed ultraviolet (UV) absorbance spectra of spent dialysate. Also, the effect of using several wavelengths (multi-wavelength algorithms) for estimation was examined. This paper gives an overview of seven studies carried out in Linköping, Sweden, and Tallinn, Estonia. A total of 60 patients were monitored over their 188 dialysis treatment procedures. Dialysate samples were taken and analysed by means of UA concentration in a chemical laboratory and with a double-beam spectrophotometer. The measured UV absorbance spectra were processed. Three models for the original and three for the first derivate of UV absorbance were created; concentrations of UA from the different methods were finally compared in terms of mean values and SD. The mean concentration (micromol/L) of UA was49.7±23.0measured in the chemical laboratory, and48.9±22.4calculated with the best estimate among all models. The concentrations were not significantly different (P≥0.17). It was found that using a multi-wavelength and processed signal approach leads to more accurate results, and therefore these approaches should be used in future.

Molecular Structure of Nitrogen in Coal from XANES Spectroscopy

1993 ◽  
Vol 47 (8) ◽  
pp. 1268-1275 ◽  
Author(s):  
Oliver C. Mullins ◽  
Sudipa Mitra-Kirtley ◽  
Jan Van Elp ◽  
Stephen P. Cramer
Keyword(s):  
Aromatic Amines ◽  
Fossil Fuel ◽  
Lone Pair ◽  
Low Rank ◽  
Model Compounds ◽  
X Ray ◽  
Chemical Structures ◽  
Pyridine Nitrogen ◽  
Low Levels ◽  
X Ray Absorption

Five major nitrogen chemical structures, present in coals of varying ranks, have been quantitatively determined with the use of nitrogen x-ray absorption near-edge spectroscopy (XANES). Similar studies of the sulfur chemical structures of coals have been performed for the last ten years; nitrogen studies on these fossil-fuel samples have only recently been realized. XANES spectra of coals exhibit several distinguishable resonances which can be correlated with characteristic resonances of particular nitrogen chemical structures, thereby facilitating analysis of these complicated systems. Many model compounds have been examined; for some, the relative peak positions are explained in terms of the orbital description of the lone pair of electrons. All features in the XANES spectra of coals have been accounted for; thus, all the major structural groups of nitrogen present in coals have been determined. A wide variety of aromatic nitrogen compounds is found in the coals; no evidence of saturated amine is found. Pyrroles, pyridines, pyridones, and aromatic amines are found in coal; of these, pyrrolic structures are the most prevalent. Pyridine nitrogen is prevalent in all except low-rank coals. The low pyridine content in low-rank (high-oxygen) coals correlates with a large pyridone content. This observation suggests that, with increasing maturation of coal, the pyridone loses its oxygen and is transformed into pyridine. Aromatic amines are present at low levels in coals of all rank. The spectral effects of aromatic amines are shown by comparing the XANES spectra of coal and petroleum asphaltenes.

scholarly journals Real-Time Estimation of Disinfection By-Products through Differential UV Absorbance

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2536
Author(s):  
Guilherme Stéphanie ◽  
Dorea Caetano
Keyword(s):  
Water Treatment ◽  
Real Time ◽  
Distribution Systems ◽  
Uv Light ◽  
Time Estimation ◽  
Uv Absorbance ◽  
Water Treatment Plants ◽  
Study Results ◽  
Real Time Estimation ◽  
By Products

Efforts to control of unwanted disinfection by-products (DBPs) can be hindered by the relatively low-frequency data that is generated from DBP monitoring for regulatory purposes. Differential UV absorbance (DUVA) has the potential to overcome some of these difficulties as a relatively simple and low-cost technique for the estimation of regulated DBPs (i.e., trihalomethanes, THMs, and haloacetic acids, HAAs). DUVA is based on the principle that differences in UV absorbance at specific wavelengths before and after chlorination can be correlated to DBP occurrence. This project sought to assess a lab-based protocol for the determination of a site-specific linear calibration curve for in situ real-time estimations of DBPs from DUVA measurement in water treatment plants (WTPs). A field spectrophotometer probe capable of high frequency scans within the UV light wavelength spectra with light paths of 100 mm was used. Models were developed to estimate DBP levels, at a scale representative of DUVA and DBP levels that actually occur in the WTP under study. Results showed that level of uncertainty on DBP levels estimation is relatively low (23% for HAAs and 32% for THMs). Although DBP estimations through DUVA are not of regulatory value, they can be used for real-time estimation of DBP levels to better inform operational decision making in water treatment plants and management of DBPs in distribution systems.

Topochemical investigation on phenolic deposits in the vessels of afzelia (Afzelia spp.) and merbau (Intsia spp.) heartwood

Holzforschung ◽  
2006 ◽  
Vol 60 (6) ◽  
pp. 583-588 ◽  
Author(s):  
Gerald Koch ◽  
Hans-Georg Richter ◽  
Uwe Schmitt
Keyword(s):  
Chemical Composition ◽  
Uv Absorbance ◽  
Pit Membrane ◽  
Parenchyma Cells ◽  
Vessel Walls ◽  
Distinct Maximum ◽  
Uv Microspectrophotometry ◽  
Absorbance Spectra

Abstract The topochemical distribution of phenolic deposits in the vessels of afzelia (Afzelia spp.) and merbau (Intsia spp.) heartwood was investigated by means of cellular UV microspectrophotometry (UMSP) to characterise the chemical composition and synthesis by pit membrane-associated enzymes. UV absorbance spectra of the deposits attached to the vessel walls of merbau are characterised by a distinct maximum at a wavelength of 368 nm representing the UV absorbance of pure robinetin (C15H10O7). Deposits in the vessels of afzelia display a typical spectrum of kaempferol (C15H10O2) with two distinct maxima at 270 and 350 nm. The pit membranes and pit canals of associated vessel and parenchyma cells are impregnated by these compounds. These results verify the assumption that the synthesis of deposits in afzelia and merbau is regulated by pit membrane-associated enzymes.

Membrane filtration for particles removal after ozonation-biofiltration

2007 ◽  
Vol 56 (10) ◽  
pp. 101-108 ◽  
Author(s):  
S. Osterhus ◽  
K. Azrague ◽  
T. Leiknes ◽  
H. Odegaard
Keyword(s):  
Membrane Reactor ◽  
Membrane Filtration ◽  
Submicron Particles ◽  
Plate Count ◽  
Uv Absorbance ◽  
Heterotrophic Plate Count ◽  
Operational Factors ◽  
Process Combination ◽  
By Products ◽  
Very High

With the process combination Ozonation-Biofiltration-Membranefiltration (the OBM-process) an average removal of 63% for UV-absorbance (UV254), 79% for color, and 28% for DOC was obtained treating NOM containing surface water. In this paper, focus has been made on the removal of particles after the ozonation and biofiltration treatment steps, using a submerged hollow fiber ultrafiltration membrane reactor. For this purpose the membrane performed adequately. The ultrafiltration step did not have a significant impact on the removal of color, UV254, and DOC. However, the SS and the heterotrophic plate count (HPC) was almost completely removed, and the turbidity was reduced by 65% by the membrane filtration, even at very high fluxes. Fouling occurred during operation, and operational factors of both the ozonation/biofiltration and the membrane reactor were important for controlling this. The experiments at pH 6.5 gave a higher permanent fouling than at pH 8.5, which was caused by the different oxidation pathways and consequently by the change in size and hydrophobicity of the by-products. On the other hand, the reversible fouling was less important at low pH. The mechanical cleaning was efficient, however, it seemed that the air scouring participated to the formation of submicron particles which favored the fouling.

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