Stopped-flow optical absorption cell

Fig. 9.4 A stopped-flow optical absorption cell equipped with two column-type cells for rapid electrolysis [7].

However, the cell in Fig. 9.2(b) has a disadvantage in that the concentration of the electrogenerated substance decreases with increasing distance from the OTE surface. Because of this, simulation of the reaction is very difficult, except for the first order (or pseudo-first-order) reactions. For more complicated reactions, it is desirable that the concentration of the electrogenerated species is kept uniform in the solution. With a thin-layer cell, a solution of uniform concentration can be obtained by complete electrolysis, but it takes 30 s. Thus, the thin-layer cell is applicable only for slow reactions. For faster reactions, a column-type cell for rapid electrolysis is convenient. Okazaki et al. [7] constructed a stopped-flow optical absorption cell using one or two column-type cells (Fig. 9.4) and used it to study the dimerization of the radical cations (TPA +) of triphenylamine and the reactions of the radical cation (DPA +) of 9,10-diphenylanthracene with water and alcohols. Using the stopped-flow cell, reactions of substances with a half-life of 1 s can be studied in solutions of uniform concentrations. 

Figure 2.14 A stopped-flow optical absorption cell equipped with two column-type cells for rapid electrolysis. R, solution reservoir DP, Nj gas bubbling EC, electrochemical cell for flow electrolysis M, mixer FC, flow-type optical absorption cell L, light beam D, photodetector, CV, control valve (23, 24).

Figure 1 A diagram of the optical arrangement of a stopped-flow system capable of simultaneous observation of changes in absorbance and fluorescence. The light from the xenon lamp is diffracted by monochromator 1 (MCMl) to select the excitation wavelength. Usually quartz optical fibres conduct the light to the observation cell and absorption is detected at 180° and fluorescence emission (wavelength selected by a cutoff filter or MCM2) Is detected at 90° relative to the incident light...

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