Pulse conductometric detection

D. Taylor and T. A. Nieman, Bipolar Pulse Conductometric Detection of Enzyme Reactions in Flow-Injection Systems. Urea in Serum and Urine. Anal. Chim. Acta, 186 (1986) 91. 

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... 

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... 

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. 

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... 

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