Conductometric pulse radiolysis

Anderson RF, Vojnovic B, Patel KB, Michael BD (1986) Reaction of alcohol radicals with cyclic disulfides. An optical and conductometric pulse radiolysis study. Radiat Phys Chem 28 219-222 Anklam E, Margaretha P (1989) Organic sulfuranyl radicals. Res Chem Intermed 11 127-155 Armstrong D (1990) Applications of pulse radiolysis for the study of short-lived sulphur species. In Chatgilialoglu C, Asmus K-D (eds) Sulfur-centered reactive intermediates in chemistry and biology. Plenum, New York, pp 121-134... 

Wagner BO, Klever H, Schulte-Frohlinde D (1974) Conductometric pulse radiolysis study on the reaction of the solvated electron with 5-bromouracil in aqueous solutions at different pH values. Z Naturforsch 29b 86-88... 

Reactions in Water.—A preliminary report has indicated that the rate of water exchange in the five-co-ordinate Co complex of (7) is particularly low for this metal (4.2 X 10 s at 25 °C) the activation parameters are given as A/f = 36.5 1.4 kJ mol and AS = — 34 4 JK mol. A preliminary application of conductometric pulse radiolysis to the dissociation of Co -amine chlorides has yielded results consistent with those obtained by other methods. The very small effect exerted by nickel(ii)-bound pyridine on the lability of the remaining water molecules has already been mentioned. An interesting preliminary report has indicated that the substitution reactions of Cu complexes are relatively slow in the absence of Jahn-Teller distortions [as, for example, in the trigonal-bipyramidal complex with (8) see Table 7]. 

Ulanski P, von Sonntag C (2000) Stability constants and decay of aqua-copper(lll) - a study by pulse radiolysis with conductometric detection. Eur J Inorg Chem 1211-1217 Vaish SP, Tollin G (1971) Flash photolysis of flavins. V. Oxidation and disproportionation of flavin radicals. J Bioenergetics 2 61-72... 

Fig. 3.1. Pulse radiolysis of N20-saturated aqueous solutions of Cu2+. Consumption of H+ as measured by conductometric changes after completion of the reaction. (Ulanski and von Sonntag 2000, with permission)...

Tripathi GNR (1998) Electron-transfer component in hydroxyl radical reactions observed by time resolved resonance Raman spectroscopy. J Am Chem Soc 120 4161-4166 TsaiT, Strauss R, Rosen GM (1999) Evaluation of various spin traps for the in vivo in situ detection of hydroxyl radical. J Chem Soc Perkin Trans 2 1759-1763 Tsay L-Y, Lee K-T, Liu T-Z (1998) Evidence for accelerated generation of OH radicals in experimental obstructive jaundice of rats. Free Rad Biol Med 24 732-737 Ulanski P, von Sonntag C (2000) Stability constants and decay of aqua-copper(lll) - a study by pulse radiolysis with conductometric detection. Eur J Inorg Chem 1211-1217 Veltwisch D, Janata E, Asmus K-D (1980) Primary processes in the reactions of OH radicals with sul-phoxides. J Chem Soc Perkin Trans 2 146-153... 

Schuchmann H-P, Deeble DJ, Phillips GO, von Sonntag C (1991) Pulse radiolysis with conductometric detection two approaches to absolute dosimetry. Radiat Phys Chem 37 157-160 Schuchmann MN, Schuchmann H-P, von Sonntag C (1989) The pJCa value of the O2CH2CO2H radical the Taft a constant of the -CEi202 group. J Phys Chem 93 5320-5323 Schuler RH, Hartzell AL, Behar B (1981) Track effects in radiation chemistry. Concentration dependence for the scavenging of OH by ferrocyanide in N20-saturated solutions. J Phys Chem 85 192-199... 

It has been a long way from the early pulse radiolysis experiments where pictures were taken from the oscilloscope screen, via the first application of a computer to record experimental curves, to today s computer-aided kinetic experiments. Such a computer-aided experiment should feature easy performance, precision in calculating data, and, most importantly, should eliminate human error. However, a certain standard in data acquisition hardware is also required, such as depicted in Fig. 5 for the simultaneous recording of two channels. The hardware for processing the electrical signals is the same for both channels allowing various detectors, such as photomultipliers, semiconductor photodiodes, or circuits for detecting conductometric... 

This discourse tries to give an overview of the current state-of-the-art instrumentation in real-time pulse radiolysis experiments utilizing optical, conductometric and other methods. Pump-and-probe techniques for the sub-nanosecond time domain are believed to be beyond the scope of this discussion. 

In this regard, pulse radiolysis studies with UV/Vis spectro-photometrical and conductometric detection were performed in model peptides containing a single methionine residue, N-Ac-Gly-(Gly) -Met-(Gly) They show for the first time that ... 

Figure 3. Schematic of a pulse radiolysis Facility with optica) and conductometric detection. C cell CS conductivity signal D dose monitor Dl door and interlock system F filters L lens MC monochromalor Mj mirrors PD pholodetector S shutter.

The chemical dosimeter that is used most frequently is the thiocyanate dosimeter [119]. Other chemical dosimeters for pulse radiolysis are ferrocyanide [119], modified Fricke (Super-Fricke) [119], hydrated electron [120], 02-saturated solutions of potassium iodide [112], and N20-saturated solutions of methylviologen and formate [118]. The C(N02)4 (tetranitromethane, TNM) dosimeter is used in pulse radiolysis experiments with simultaneous optical and conductometric detection [121-124]. The composition and characteristics of the various chemical dosimeters used for pulse radiolysis with optical detection are listed in Table 8. 

C02 can also be generated by ionizing radiation in aqueous solutions [114]. For instance, the radical anion can be produced by reaction of hydroxyl radicals or H atoms with formic acid/formate ion, hydroxyl radicals with carbon mmioxide, or solvated electrons with carbon dioxide [115]. In these experiments, the hydroxy carbonyl radical OCOH can also form, (1.13)-(1.16). The latter radical is the protonated form of the CO2 radical anion (1.16). The pKa of OCOH has been a matter of several experimental determinations resulting in significantly different values found for this quantity. A p/sTa (0C0H/C02 ) value of 2.3 has been quite recently determined by von Sonntag et al. [115] by using pulse radiolysis with conductometric detection. 

Hissung A, von Sonntag C (1978) Radiolysis of cytosine, 5-methylcytosine and 2 -deoxycytidine in deoxygenated aqueous solution. A pulse spectroscopic and pulse conductometric study of the OH adduct. Z Naturforsch 33b 321—328... 

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