Irradiation detection methods

A procedure for determination of lipid hydroperoxides in human plasma is based on kinetic measurement of the CL of luminol (124) with hemin (75a) catalysis . CLD of microperoxidase-catalyzed oxidation of luminol (124) or isoluminol (190) was applied to detection and determination of amino acid hydroperoxides after exposure to UV and y-irradiation A method for determination of hydroperoxides in the phospholipids of cultured cells uses isoluminol (190) and microperoxidase as catalyst " . Simultaneous determination of phosphatidylcholine hydroperoxides and cholesteryl ester hydroperoxides in human serum is carried out by quantitative extraction of the lipids, HPLC separation by column switching and CLD using isoluminol (190) with microperoxidase catalysis . ... 

Significant progress has been made in the field of analytical detection of irradiated food to improve consumers confidence and to assist international trade of irradiated food [135,136]. Due to national and international programs and activities of the European Committee for Standardization (CEN), five validated and standardized detection methods are now available. The CEN is also considering the adoption of further five detection methods three will be screening methods (positive results from a screening method must be confirmed using a standardized method) [136]. 

Borsa, J. Chu, R. Sun, J. Linton, N. Hunter, C. Radiat. Phys. Chem. 2002, 63, 271. Murray, C.H., Stewart, E.M., Gray, R., Pearce J. Eds. Detection Methods for Irradiated Foods—Current Status) The Royal Society of Chemistry, Information Services London, 1996. Delincee, H. Radiat. Phys. Chem. 2002, 63, 455. 

Anon. (1992). Coordinated Research Programme on Analytical Detection Methods for Irradiation Treatment of Foods (ADMIT). Second Research Co-ordination Meeting, Hungary, 15-19 June, IAEA, Vienna, 15. 

Delincee, H. (1993). Control of irradiated food Recent developments in analytical detection methods. Radiat. Phvs. Chem. 42. 351. 

Schreiber, G.A., Helle, N. and Bogl, K.W. (1993a). Detection of irradiated food - Methods and routine applications. Int, J, Radiat. Biol. 63. 105. 

Another label-free optical detection method—FTIR-ATR—has been applied for detection of thrombin by means of DNA aptamers [73], The antithrombin DNA aptamer previously developed by Tasset et al. [17] was immobilized covalently onto Si surface using UV irradiation method. As a quantitative measure, the area of N-H and CH2 bands was used. This method allowed to detect thrombin with a sensitivity around 10 nmol/L. The specificity of binding of protein to aptamer was also investigated using DNA with no binding site for thrombin. It has been noted that for effective binding study by FTIR-ATR method, the concentration of protein should be kept lower than 100 nmol/L. 

Illuminated alternately with UV and visible light, the porphyrinic dithienylethene underwent a reversible photoisomerization reaction (Scheme 1). Meanwhile, the fluorescence intensity of the porphyrin macrocycles could be regulated by alternate irradiation with UV (313nm) and visible light (longer than 480 nm). Moreover, the selective excitation band of the fluorophore was beyond the spectral band which could induce the photoisomerization reaction. Therefore, the authors asserted that this compound could act as a system for reversible data processing using fluorescence as the non-destructive detection method. 

It is from these perspectives that we have reviewed the pulse radiolysis experiments on polymers and polymerization in this article. The examples chosen for discussion have wide spread interest not only in polymer science but also in chemistry in general. This review is presented in six sections. Section 2 interprets the experimental techniques as well as the principle of pulse radiolysis the description is confined to the systems using optical detection methods. However, the purpose of this section is not to survey detail techniques of pulse radiolysis but to outline them concisely. In Sect. 3, the pulse radiolysis studies of radiation-induced polymerizations are discussed with special reference to the initiation mechanisms. Section 4 deals with applications of pulse radiolysis to the polymer reactions in solution including the systems related to biology. In Sect. 5 reaction intermediates produced in irradiated solid and molten polymers are discussed. Most studies are aimed at elucidating the mechanism of radiation-induced degradation, but, in some cases, polymers are used just as a medium for short-lived species of chemical interest We conclude, in Sect. 6, by summarizing the contribution of pulse radiolysis experiments to the field of polymer science. 

Many detection methods have been discussed in the literature [3,9,10], but considerable progress has been made, due to the IAEA ADMIT program and, mainly, to the European concerted actions [11-14]. We briefly describe here the published European protocols leading to a proof of irradiation or a proof of no irradiation (Tab. 2). 

McMurray C., Stewart E., Gray R., Rearce J., Detection methods for irradiated foods, current status. Royal Chem. Soc, 1996. 

Specific detection is an analytical determination based on specific responses related to the chemical characteristics of a molecule excited by a certain type of irradiation. In this detection method, measurement of the molecule of interest may usually be performed without separation from matrix materials or from other ingredients if appropriate instrumental adjustments are made. The need for identification and structure elucidation for newly discovered compounds drives the progress of specific detection techniques with NMR and X-ray diffraction and MS. The UV-diode array detector often aids the recognition of chromatographic peak purity, ensuring complete resolution of a separation procedure. 

Apart from product analysis and ESR studies on the free radicals generated by the irradiation, other methods for the detection of the generated free radicals have been used. This area is of some synthetic value since it can be shown that the irradiation using a tungsten lamp of benzenesulphonyl chloride in the presence of either cis- or trans-but-2-ene affords 1 1 adducts 312,13. Photoaddition of p-toluenesulphonyl chloride to norbor-... 

Thus, any successful kinetic analysis requires an optimal choice of the spectroscopic detection method, whereby special methods (e.g. pre-separation by chromatography) or modem approaches (e.g. interferometry) must also be considered. Therefore in the following sections different approaches in spectroscopy are presented, some combined irradiation and measurement devices introduced, and different set-ups classified with respect to their principle of operation (sequential, multiplex, single and double beam equipment). In addition some special devices are presented which allow an automated examination even of complex photochemical reactions (in part superimposed by thermal reactions) at a highly sophisticated level using various combinations of modem equipment and supplying data for multicomponent analysis. 

Recording of the ESR spectrum under simultaneous irradiation of the sample by an electron beam was used in the first experiments [7], In later studies pulsed ESR was used in pulse radiolysis experiments [8]. This detection method has a high time resolution of ca. 10 ns for studies of reaction kinetics. Radicals formed by steady state photolysis were also studied at an early stage. Pulsed ESR is commonly used with laser flash photolysis to obtain high time resolution in modern applications [9]. For studies of radicals formed in chemical reactions a common method is by mixing of the reagents in a flow system before entering the ESR cavity. In these in sim experiments the ESR lines can occur in emission rather than absorption because the radicals are not in thermal equilibrium immediately after formation. A chemically induced electron polarization, CIDEP, occurs. 

McMurray CH, Stewart EM, Gray R, Pearce J.. Detection Methods for Irradiated Foods-Current Status. Cambridge (United Kingdom) The Royal Society of Chemistry. 431 p. (1996). 

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