Thermal features of radiation induced radical of gamma irradiated gallic acid

Öz

In the present work, temperature effects of gamma irradiated anhydrous and monohydrate gallic acid components were investigated using Electron Paramagnetic Resonance (EPR) spectroscopy.  While unirradiated samples presented no EPR signal, irradiated samples were observed to exhibit an EPR spectrum consisting of an intense resonance line at the middle and weak lines on both sides.  Thermal features of the radicals responsible of experimental EPR spectrum were explored trough the variations of the peak-to-peak amplitude and spectrum area under the EPR spectra.  Also the high temperature annealing stability of the radicals was investigated.  It is calculated that the activation energies of the main two radicals that contributed to the experimental spectra of GA-a and GA-m compounds was 64.68 kJ/mol and 88.11 kJ/mol, and 35.88 kJ / mol and 127.64 kJ/mol, respectively.

Anahtar Kelimeler

• Electron Paramagnetic Resonance (EPR),gallic acid,irradiation,thermal features

Gama radyasyonu ile ışınlanan gallik asitte oluşan radikallerin termal özellikleri

Öz

Bu çalışmada sıcaklığın, gama radyasyonu sonucunda gallik asit anhydrous (GA-a) ve gallik asit monohydrate (GA-m) bileşenlerine olan etkisi Elektron Paramanyetik Rezonans (EPR) spektroskopisi kullanılarak incelenmiştir.  Işınlanmamış örneklerde herhangi bir EPR sinyali gözlenmezken, ışınlanmış örnekler merkezde ve her iki tarafında yer alan bir EPR spektrumu verdiği gözlenmiştir.  Deneysel EPR spektrumuna kaynaklık eden radikallerin termal özellikleri tepeden-tepeye sinyal şiddeti ve spektrum altında kalan alan dikkate alınarak araştırılmıştır.  Ayrıca radikallerin yüksek sıcaklıkta tavlama sonucunda radikallerin kararlılığı araştırılmıştır.  GA-a ve GA-m örneklerinin deneysel spektrumlarına katkı getiren iki ana radikalin aktivasyon enerjileri sırasıyla 64.68 kJ/mol ve 88.11 kJ/mol, ve 35.88 kJ/mol ve 127.64 kJ/mol olduğu hesaplanmıştır.

Anahtar Kelimeler

• Elektron Paramanyetik Rezonans (EPR),gallik asit,ışınlama,termal özellikler

Kaynakça

1. [1] Friedman, M., and Jürgens, H.S.J., Effect of pH on the stability of plant phenolic compounds. Journal of Agricultural and Food Chemistry, 48, 2101-2110 (2000)
2. [2] Taniguchi, H., andSchuler, R.H., An ESR study of the dissociation of hydroxyl protons in hydroxycyclohexadienyl radicals. The Journal of Physical Chemistry, 89, 3095-3101 (1985)
3. [3] Eslami, A.C., Pasanphan, W., Wagner, B.A., and Buettner, G.R., Free radicals produced by the oxidation of gallic acid: An electron paramagnetic resonance study. Chemistry Central Journal 4, 15-18 (2010)
4. [4] Zhao, J., Khan, I.A., and Fronczek, F.R., Gallic Acid. Acta Crystallographica Section E. 67, O316–O317 (2011)
5. [5] Melo, R., Leal, J.P., Takács, E., and Wojnárovits, L., Radiolytic degradation of gallic acid and its derivatives in aqueous solution. Journal of Hazardous Materials172, 1185-1192 (2009)
6. [6] Melo, R.P.,; Leal, J.P., and Botelho, M.L., Radiolytic degradation mechanism of gallic acid and its end-products. Rapid Communications in Mass Spectrometry 25, 218-222 (2011)
7. [7] Tuner H, Bal M. O., and Polat M., Radiation sensitivity and EPR dosimetric potential of gallic acid and its esters, Radiation Physics and Chemistry, 107, 1, 115-120 (2015).
8. [8] Tuner, H., EPR spectral investigation of radiation-induced radicals of gallic acid, submited.

9. [9] Weil, J.A., Bolton, J.R., and Wertz, J.E., Electron Paramagnetic Resonace, Elementary theory and applications, John Wiley & Sons, New York, p. 481 (1994)