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1

Recent upgrading of the nanosecond pulse radiolysis setup and construction of laser flash photolysis setup at the Institute of Nuclear Chemistry and Technology in Warsaw, Poland

Szreder Tomasz

Nukleonika

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2022

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Vol. 67, No. 3

49--64

EN

Modification of pulse radiolysis (PR) setup and construction of a new laser flash photolysis (LFP) setup at the Institute of Nuclear Chemistry and Technology (INCT) is described. Both techniques are dedicated to studying fast reactions in real time by direct observation of transients. Time resolution of the PR setup at INCT was ~11 ns, limited by the duration of the electron pulse. Implementation of a new spectrophotometric detection system resulted in a significant broadening of experimental spectral range with respect to the previous setup. Noticeable reduction of the noise-to-signal ratio was also achieved. The LFP system was built from scratch. Its time resolution was ~6 ns, limited by the duration of a laser pulse. LFP and PR were purposely designed to share the same hardware and software solutions. Therefore, components of the detection systems can be transferred between both setups, signifi cantly lowering the costs and shortening the construction/upgrading time. Opened architecture and improved experimental fl exibility of both techniques were accomplished by implementation of Ethernet transmission control protocol/Internet protocol (TCP/IP) communication core and newly designed software. This is one of the most important enhancements. As a result, new experimental modes are available for both techniques, improving the quality and reducing the time of data collections. In addition, both systems are characterized by relatively high redundancy. Currently, implementation of new equipment into the systems hardly ever requires programming. In contrast to the previous setup, daily adaptations of hardware to experimental requirements are possible and relatively easy to perform.

2

Intermediates derived from p-terphenyl in the methyltributylammonium bis[(trifluoromethyl)sulfonyl]imide ionic liquid saturated with carbon dioxide : pulse radiolysis study

Kocia Rafał

Nukleonika

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2022

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Vol. 67, No. 4

73--80

EN

Radiation-induced processes in ionic liquid (IL) methyltributylammonium bis[(trifl uoromethyl)sulfonyl] imide ([MeBu3N][NTf2]) solutions containing p-terphenyl (TP) and saturated with carbon dioxide (CO2) were studied using nanosecond pulse radiolysis technique with UV-vis detection. The transient absorption spectra generated in these solutions were assigned to TP radical anions (TP•–) and triplet excited states (3TP*). Saturation of [MeBu3N][NTf2] solutions with carbon dioxide efficiently takes out presolvated electrons (e–presolv) and solvated electrons (e–solv). On the other hand CO2 is not a scavenger of excited states of TP (1TP*, 3TP*), which in the reaction with triethylamine (TEA) leads to the formation of TP•-.

3

Zastosowanie metod analitycznych w wykrywaniu napromieniowania żywności. : przegląd najnowszych metod w świetle regulacji unijnych : radioliza pulsowa, spektroskopia w podczerwieni i ramanowska w analizie napromieniowanej żywności

Lewandowska H., Jakubczak A., Świsłocka R., Stachelska M. A., Lewandowski W.

Aparatura Badawcza i Dydaktyczna

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2012

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T. 17, nr 4

79-85

PL

Napromienianie żywności jest metodą konserwacji o niemal stuletniej tradycji. Pomimo, że zostało zaakceptowane przez organy kontroli jakości w wielu krajach na całym świecie, nadal budzi kontrowersje. Nie ulega kwestii, że procesy napromieniania żywności powinny być monitorowane, a żywność sterylizowana radiacyjnie powinna podlegać bardzo ścisłej kontroli jakości. Z tej przyczyny poszukuje się nowych metod wykrywania i dozymetrii napromieniowanej żywności. Obecnie wśród metod analitycznych wykrywania żywności poddanej napromieniowaniu, znormalizowanych przez Europejski Komitet Normalizacyjny (CEN), są tylko dwie metody spektroskopowe: rezonans paramagnetyczny i luminescencja stymulowana światłem, jednak badania wskazują na możliwość zastosowania wielu innych dogodnych rozwiązań z zastosowaniem m.in. spektroskopii Ramana i widm w bliskiej podczerwieni. Spektroskopowe metody oceny napromieniowanej żywności dają możliwość szybkiego i precyzyjnego wykrycia zastosowanych dawek, dlatego zasługują na zainteresowanie ze strony zespołów badawczych i wdrożeniowych. Niniejszy przegląd omawia krótko obecny stan naukowy i prawny monitoringu napromieniowania artykułów żywnościowych w Polsce i na świecie, a następnie prezentuje najnowsze doniesienia i osiągnięcia w zakresie zastosowania metod spektroskopowych w ocenie napromienionej żywności.

EN

Food irradiation as a method of preservation is nearly a century old. Although it has been approved by the quality control in many countries around the world, it still remains a matter of controversy. There is no question that the process of food irradiation should be monitored, and irradiated foods should be subject to very strict quality control. For this reason the search for new methods of detection and dosimetry of irradiated foods is required. Currently, among the analytical methods for detecting irradiated foods standardized by the European Committee for Standardization (CEN) only two are the spectroscopic methods: EPR and photostimulated luminescence, but studies indicate the possibility of using a number of other convenient solutions, among others Raman and near-infrared spectra. Spectroscopic methods for assessing irradiated foods make it possible to quickly and accurately detect the applied dose, and shall draw attention of the research and implementation teams. This review briefly discusses the current scientific and legal status of irradiated food monitoring in Poland and worldwide and presents the latest achievements in the application of spectroscopic methods in the evaluation of food irradiation.

4

The mechanism and kinetics of ozone formation in a pulse radiolysis study of the Ar-O2 system

Wojciechowski K., Sugier D., Wnorowski K., Kowalczyk J., Jówko A.

Nukleonika

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2005

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Vol. 50,suppl.2

29-33

EN

The mechanism and kinetics of O3 formation after an electron pulse have been studied in the Ar-O2 systems by time resolved optical measurements at gamma = 260 nm. The second order rate constant of energy transfer from excited Ar(4s,4p) states to O2 molecules: (1) Ar*,Ar** + O2 → O2* + Ar, was found to be (8.9 ± 2.1) x 10-10 cm3 s-1. It was found also the evidence of the third order process contribution to the energy transfer: (2) Ar*,Ar** + Ar + O2 → products, with the rate constant in the range (1.5-3.7) x 10-29 cm6 s-1. The rate constant of the deactivation of excited ozone molecules by O2 was found to be (5.1 ± 0.6) ´ 10-15 cm3 s-1.

5

Free radicals in chemistry, biology and medicine: contribution of radiation chemistry

Bobrowski K.

Nukleonika

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2005

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Vol. 50,suppl.3

67-76

EN

The scope of this article is limited to the concept of free radical and its historical background and a brief introduction to time-resolved techniques (pulse radiolysis, laser flash photolysis), which allowed direct observation of free radicals on real time. The selected contributions of pulse radiolysis to better understanding the role of free radical reactions in chemistry, biology and medicine are presented and some selected future research needs and opportunities in radiation chemistry are briefly addressed.

6

Formation of Br2 '-, BrSCN'- and (SCN)2'-intermediates in the ionic liquid methyltributylammonium bis[(trifluoromethyl)sulfonyl]imide. Pulse radiolysis study

Grodkowski J., Nyga M., Mirkowski J.

Nukleonika

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2005

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Vol. 50,suppl.2

35-38

EN

The reactions of Br2 '- anion radicals with thiocyanate anions in the ionic liquid methyltributylammonium bis[(trifluoromethyl)sulfonyl]imide (R4NNTf2) were studied by pulse radiolysis. Reaction of solvated electrons with BrCH2CH2Br (DBE), k = (1 2)×108 L.mol 1.s 1, leads to the production of Br2'- anion radicals. The intermediate absorption spectra following pulse radiolysis of DBE/SCN-/Br-/ solutions in R4NNTf2 correspond to Br2 '-, BrSCNo- and (SCN)2'- anion radicals. The participation of these radicals in the spectra changes with progressing reactions and depends on the concentration Br- and SCN- in the solution.

7

Radiation chemistry of solid thiosulfate: optical absorption spectra

Zagórski Z., Rafalski A.

Nukleonika

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2000

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Vol. 45, nr 1

109-113

EN

Solid sodium thiosulfate, anhydrous and hydrated (5 H2O), was irradiated with 10 MeV electrons in a pulsed, high-dose (30 kGy) rate regime. The resulting optical absorption was measured by diffuse reflection spectophotometry (DRS) (absorption band in anhydrous salt at 360 nm, in hydrated salt at 418 nm). Absorption decays occurred at t1/2 = 80 h (anhydrous) and t1/2 = 9 h (hydrated) at room temperature. The yellowish radical ion formed in irradiated anhydrous thiosulfate was identified as [źS2O3]-, and not [źS2O3]3-, as proposed in previous nonoptical (EPR) investigations. The absorption spectrum of [źS2O3]- in a solid matrix was similar to the transient spectrum ascribed to the same radical, obtained by pulse radiolysis in aqueous solution, and had a lifetime many orders of magnitude shorter. A similar radical anion, but in the complex with adjacent water molecules from the hydration moiety, was observed in hydrated thiosulfate (Na2S2O3ź5 H2O).

8

Oxidation of organic sulfides by peroxyl radicals; search for an adduct intermediate

Bonifacic M., Stefanic I.

Nukleonika

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2000

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Vol. 45, nr 1

39-44

EN

The reaction mechanism of dimethyl sulfide oxidation by peroxyl radicals (CCl3OOź and CHCl2OOź) in aqueous/alcohol solutions has been studied by means of pulse radiolysis with optical detection in order to gain evidence for the formation of an adduct intermediate, ROO-źS(CH3)2. In the range of 300-650 nm, the only absorbing product was the one-electron oxidized species [(CH3)2S\S(CH3)2]+, and no indication of an additional absorption attributable to an adduct precursor was found. Under the condition of only 50% conversion of CHCl2OOź into the sulfide radical cation, however, addition of a small amount of I- resulted in formation of (CH3)2S\I as the only product and at a yield equal to that of CHCl2OOź radicals. This result is explained by the reaction of iodide ions with a precursor of [(CH3)2S\S(CH3)2]+ species, namely, the adduct CHCl2OO-źS(CH3)2 and is, thus, taken as conclusive, although indirect, evidence of the existence of this adduct intermediate.

9

Free-radical chemistry of thiourea in aqueous solution, induced by OH radical, H atom, a-hydroxyalkyl radicals, photoexcited maleimide, and the solvated electron

Schuchmann M., Schuchmann H., Knolle W., von Sonntag J., Naumov S., Wang W., von Sonntag C.

Nukleonika

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2000

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Vol. 45, nr 1

55-62

EN

Hydroxyl radicals react with thiourea (and its tetramethyl derivative) yielding dimeric radical cations which are characterized by strong absorptions at 400 nm (450 nm). An analysis of the kinetics of the buildup of these absorptions gives evidence for the intermediacy of OH-adducts and the monomeric radical cations. The dimeric radical cations are also generated in the reactions of triplet-excited maleimide with these thioureas. Moreover, in acid solutions even reducing radicals such as the H atom and a-hydroxyalkyl radicals give rise to these intermediates in full yields, albeit displaying different kinetics. Potential mechanistic implications are discussed. The dimeric thiourea radical cations are strong oxidants and readily oxidize the anions of phenol and 2’-deoxyguanosine. The solvated electron gives rise to an intermediate which is rapidly protonated by water (pKa > 11). Quantum-mechanical calculations support the assignment of the 400 nm (450 nm) absorption to the respective dimeric thiourea radical cation.

10

Measurement system for pulse radiolysis at the linear electron accelerator LAE 13/9

Mirkowski J., Grodkowski J.

Nukleonika

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1999

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Vol. 44, nr 1

71-78

EN

A new control and measurement system for a pulse radiolysis setup based on the linear electron accelerator LAE 13/9 is described. It consists of CAMAC apparatus, two oscilloscopes: Tektronix TDS620 and Iwatsu TS8123, and a PC computer as a central unit for programming and controlling of the experiments and for results processing. The program is written using DELPHI 1.0 (Borland) programming platform and it can operate in WINDOWS 3.x or WINDOWS 95 environment.

PL

Opisano nowy system kontrolno - pomiarowy do radiolizy impulsowej opartej na liniowym akceleratorze elektronów LAE 13/9 Żerań. W jego skład wchodzą: aparatura systemu CAMAC, dwa oscyloskopy - Tektronix TDS620 i Iwatsu TS8123, komputer PC jako centralna jednostka do programowania i kontrolowania eksperymentów oraz przeliczania wyników. Program jest napisany przy użyciu pakietu DELPHI 1.0 (Borland) i jest przystosowany do środowiska WINDOWS 3.x i WINDOWS 95.