Electron Spin Resonance (ESR) Spectroscopy

1992 ◽  
pp. 274-286 ◽  
Author(s):  
D. N.-S. Hon
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Esr Spectroscopy ◽  
Spin Resonance

scholarly journals Antioxidant activity of Induna apple pomace extract

2005 ◽  
pp. 239-246 ◽  
Author(s):  
Sladjana Savatovic ◽  
Sonja Djilas ◽  
Vesna Tumbas ◽  
Jasna Canadanovic-Brunet ◽  
Gordana Cetkovic
Keyword(s):  
Aqueous Solution ◽  
Antioxidant Activity ◽  
Acetic Acid ◽  
Electron Spin Resonance ◽  
Hydroxyl Radicals ◽  
Electron Spin ◽  
Esr Spectroscopy ◽  
Methanol Extract ◽  
Apple Pomace ◽  
Spin Resonance

Different concentrations ofmethanol aqueous solution with or without 0.5% acetic acid and 80% acetone were used to achieve the highest yield of extraction of phenolics from Induna apple pomace. The highest content of phenolics (6.38 mg/g) was detected in the 80% methanol extract. The influence of 80% methanol extract of Induna apple pomace on stable l,l-diphenyl-2-picrylhydrazyl (DPPH) and reactive hydroxyl radicals has been investigated by electron spin resonance (ESR) spectroscopy. Based on the obtained results it can be concluded that the investigated extract is more effective in the DPPH test than on the DMPO-OH scavenging. In both cases antioxidant activity increased with increasing concentration of the investigated extract. The high contents ofphenolics (6.38 mg/g), flavonoids (1.01 mg/g) and flavan-3-ols (0.70 mg/g) in 80% methanol extract indicated that these compounds contributed to the antioxidant activity of Induna apple pomace.

Electron spin resonance (ESR) spectroscopy study of cheese treated with accelerated electrons

2019 ◽  
Vol 276 ◽  
pp. 315-321 ◽  
Author(s):  
Rosa Escudero ◽  
Jose Segura ◽  
Raquel Velasco ◽  
Margarita Valhondo ◽  
M. Dolores Romero de Ávila ◽  
...  
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Esr Spectroscopy ◽  
Spectroscopy Study ◽  
Accelerated Electrons ◽  
Spin Resonance

An ESR and calorimetric study of iron oolitic samples from the Northampton ironstone

Clay Minerals ◽  
1990 ◽  
Vol 25 (3) ◽  
pp. 303-311 ◽  
Author(s):  
A. U. Gehring ◽  
R. Karthein
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Hyperfine Splitting ◽  
Esr Spectroscopy ◽  
Thermal Conversion ◽  
Esr Spectra ◽  
Calorimetric Study ◽  
Calorimetric Methods ◽  
Mineral Phases ◽  
Spin Resonance

AbstractElectron spin resonance (ESR) spectroscopy and calorimetric methods were used to characterize conversion processes in multimineral samples from the Northampton ironstone (NIS) at temperatures between 25°C and 800°C. The beginning of the thermal conversion processes can be determined by the formation of asymmetric ESR spectra with g ≈ 2 at 250°C. The breakdown of the berthierine structure between 250°C and 520°C is indicated by the disappearance of the hyperfine splitting in the Mn2+ spectrum and the formation of magnetite. The decomposition of siderite and calcite was found by calorimetric methods at 580°C and 700°C, respectively. The hematite formation between 550°C and 800°C is explained by the decomposition of siderite but also by the oxidation of previously formed magnetite. The occurrence of hematite as the dominant ferric oxide at 800°C signifies the end of the conversion process of the major mineral phases in the NIS samples.

scholarly journals 1P121 Analysis of Daphnia resting eggs by electron spin resonance(ESR) spectroscopy

2004 ◽  
Vol 44 (supplement) ◽  
pp. S60
Author(s):  
M. Sakata ◽  
T. Kawasaki ◽  
T. Shibue ◽  
A. Takada ◽  
H. Yoshimura ◽  
...  
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Esr Spectroscopy ◽  
Resting Eggs ◽  
Spin Resonance

Investigation of Gamma Radiation on Hydroxyapatite Synthesized from Chicken Eggshell by ESR Spectroscopy

2015 ◽  
Vol 1125 ◽  
pp. 416-420
Author(s):  
Kanokwan Boonsook ◽  
Weeranuch Kaewwiset ◽  
Ekachai Hoonnivathana ◽  
Pichet Limsuwan ◽  
Kittisakchai Naemchanthara
Keyword(s):  
Electron Spin Resonance ◽  
Gamma Radiation ◽  
Electron Spin ◽  
Esr Spectroscopy ◽  
Chemical Precipitation ◽  
Precipitation Method ◽  
Spin Resonance ◽  
Chicken Eggshell ◽  
Radiation Induced ◽  
Gamma Irradiated

The purpose of this work was investigated the properties and characteristic of gamma radiation on hydroxyapatite which synthesized from biowaste chicken eggshell via the chemical precipitation method. The hydroxyapatite from biowaste chicken eggshell was gamma irradiated in rage 10 Gy to 1 kGy and analyzed by electron spin resonance (ESR). The optimize parameter set ESR read out of Hydroxyapatite were such as microwave power and modulate amplitude corresponded 63.34 mW and 2 mT, respectively. The ESR signal based on the measurement of the concentration of radiation induced radicals CO2- molecular ion also formed in hydroxyapatite. The relative of ESR intensity and dose response was linear. These experiments indicated that the hydroxyapatite from biowaste chicken eggshell could be used good dosimeter in rage 20 to 100 Gy.

An electron spin resonance and CIDEP study of the photoreduction of tert-butyl-p-benzoquinones

1978 ◽  
Vol 56 (6) ◽  
pp. 869-877 ◽  
Author(s):  
Terry Foster ◽  
A. John Elliot ◽  
Babatunde B. Adeleke ◽  
Jeffrey K. S. Wan
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Chemical Equilibrium ◽  
Esr Spectroscopy ◽  
Semiquinone Radical ◽  
Phenoxy Radical ◽  
Decay Kinetics ◽  
Tert Butyl ◽  
Semiquinone Radicals ◽  
Spin Resonance

The photoreduction of 2-tert-butyl-p-benzoquinone and 2,5- and 2,6-di-tert-butyl-p-benzoquinone were studied by esr spectroscopy. In the photolysis of 2,6-di-tert-butyl-p-benzoquinone, only one semiquinone radical was observed and its decay kinetics were monitored by esr. The reduction of the triplet 2-tert-butyl-p-benzoqinone leads to the formation of isomeric semiquinone radicals 1 and 2 in the primary photochemical processes, and this is then followed by a chemical equilibrium between the two isomeric radicals. The relative rates of formation of the two radicals cannot be monitored by conventional esr methods but the CIDEP results show that the formation of radical 2 is about five to seven times faster than that of radical 1. A secondary reaction of the phenoxy radical with a product benzohydrofuran 4 leads to the observation of a polarized radical 3 which derives all its polarization from the primary phenoxy radical.

Trifluoromethylphenylcarbenes. Carbene-Carbene Interconversion on the Singlet Energy Surface and Rearrangement to Trifluorobenzocyclobutene, Trifluorostyrene, and Trifluoromethylfulvenallenes

2015 ◽  
Vol 68 (1) ◽  
pp. 36 ◽  
Author(s):  
Rodney J. Blanch ◽  
Curt Wentrup
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Esr Spectroscopy ◽  
Energy Surface ◽  
Esr Spectra ◽  
Intersystem Crossing ◽  
Triplet States ◽  
Long Wavelength ◽  
Spin Resonance ◽  
Triplet Carbenes

The four isomeric α-, ortho-, meta-, and para-trifluoromethylphenylcarbenes were generated by photolysis of the corresponding 3-phenyl-3-trifluoromethyldiazirene 1 or the four isomeric trifluoromethylphenyldiazomethanes 2 and 4–6. The four corresponding triplet trifluoromethylphenylcarbenes 3 and 7–9 were observed by electron spin resonance (ESR) spectroscopy in Ar matrices at 14 K. The α- and ortho-carbenes 3 and 7 and the ortho- and para-carbenes 7 and 9 interconvert partially when generated by short-wavelength photolysis (350 nm) before intersystem crossing to the triplet states. The triplet states do not undergo further Carbene-Carbene interconversion. The interconversions are assumed to take place via the meta-trifluoromethylphenylcarbene 8. When the ortho- and para-carbenes are generated by long-wavelength photolysis (>450 nm), the discrete, non-interconverting triplet carbenes are observed in the ESR spectra. Flash vacuum thermolysis of the diazirene 1 at 500°C afforded a mixture of bis(trifluoromethyl)heptafulvalenes 11, bis(trifluoromethyl)stilbenes 12, and bis(trifluoromethyl)anthracenes 13, and the presence of their likely precursor(s), trifluoromethylcycloheptatetraene(s), was confirmed by a peak at 1830 cm–1 in the Ar matrix IR spectrum. In addition, at 700°C, four monomeric carbene rearrangement products were isolated and characterised, viz. 1,1,2-trifluorobenzocyclobutene 14, 1′,2′,2′-trifluorostyrene 15, and 1- and 2-trifluoromethylfulvenallenes 16 and 17.

Electron Spin Resonance Study of Phenolic Antioxidants. Correlations of Organic Free Radical Stability with Antioxidant Activity

1972 ◽  
Vol 45 (2) ◽  
pp. 402-422 ◽  
Author(s):  
J. C. Westfahl ◽  
C. J. Carman ◽  
R. W. Layer
Keyword(s):  
Molecular Structure ◽  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Esr Spectroscopy ◽  
Spectroscopic Technique ◽  
Electron Spin Resonance Study ◽  
Phenolic Antioxidants ◽  
Radical Concentration ◽  
Spin Resonance

Abstract Electron spin resonance (ESR) is a well established, sensitive spectroscopic technique for determining the molecular structure, as well as the lifetime or stability of organic free radicals. Consequently, ESR spectroscopy provides a logical method for gaining insight into the role that free radicals play in the stabilization of rubber by organic antioxidants. We used ESR spectroscopy to determine the molecular structure of the phenoxyl free radicals derived from a series of twelve phenolic antioxidants. We also used ESR to measure relative radical concentrations of the free radicals and evaluated the twelve phenolic antioxidants relative to each other. We have found that the ESR measurement of relative radical concentration is a measure of relative radical stability, and that the relative radical stability is temperature dependent. By plotting relative radical concentration (or stability) as a function of temperature, we can rank these twelve antioxidants relative to each other. This ranking is in good agreement with the activity of these antioxidants in EPDM. These data were discussed in relation to antioxidant mechanism.

Sign in / Sign up

Export Citation Format

Share Document