Chronocoulometric measurements

R. A. Osteryoung and coworkers [5] have performed chronocoulometric measurements of surface charge density at a controlled-growth mercury electrode. After initial formation and equilibration of the mercury drop, it was expanded by further addition of mercury and the charge corresponding to the new area was directly measured. The obtained value... 

The results of potential-dependent chronocoulometric measurements suggested the mechanism of Scheme 4 for the reaction sequence, where ArH is acridine and (ArHAr)+ is 101 or 102.347 The rate constant for the addition of acridine to its cation-radical was determined as 1.3 x 105 liter mol-1 sec-1. 

Viologens are electroreduced in two pH-independent electron-transfer steps, y2+ v+ and V" " —> Chronocoulometric measurements on the lipophilic dioctadecylviologen (henceforth... 

Rinse the electrode with a large amount of washing buffer and blow-dry electrode under a gende stream of nitrogen before chronocoulometric measurement. 

Fig. 3. Chronocoulometric measurement. Representative chronocoulometric curves of signal-on aptasensor for the control sample without ATP (C( J and the sample with ATP (< sainpie)- Intercepts at f=0 In chronocoulometric curves represent redox charges of RuHex bound to DMA. Signal Is defined as the difference In the redox charge of RuHex with and without ATP treatment, which Is equal to the difference In the chronocoulometric Intercept at t= 0 with and without ATP treatment (signal = Q3, ,p 3-...

Recently, the single-step chronocoulometry has been applied to Cd(II) + KBr(l M)/Cd(am) system in the paper [219]. The potential steps starting in the pre-faradaic potential range and ending at the limiting current plateau enable the evaluation of reactant surface excess. Fa, corrected for double-layer charging. Chronocoulometric measurements led to a plausible adsorption isotherms for Cd(II) complex and... 

With a combination of in situ conductivity and potential-step chronocoulometric measurements, Harima et al. [988] studied the enhancement of carrier mobilities in poly(3-methylthiophene). In addition to the obvious effect of the electrochemically induced increase in the concentration of mobile charge carriers, a drastic mobility enhancement of over 4 orders of magnitude, which implies a change from hopping to metallic transport, was concluded. 

Chronocoulometry belongs to the family of step techniques. The essential features of chronoamperometry have already been discussed in Chap. 1.3.2. Instead of following the variation of current with time after application of a potential step perturbation, it is possible to detect the amount of the charge passed as a function of time, i.e., to carry out chronocoulometric measurements. Chronocoulometry gives practically the same information that is provided by chronoamperometry, since it is just an integrated form of the current-time response, however, chronocoulometry offers important experimental advantages. 

Under the experimental conditions, the rate constant for the bare gold electrode was 9.1xl0 0.2xl0 " cm/s and 1.2X10 0.2 x 10 " cm/s for the M-DNA/hydroxylalkyl-modified Au electrode. Interestingly, for ds-DNA/hydroxylalkyl-modified Au electrode, was too small to be measured. This indicates that Icei for native ds-DNA must be orders of magnitude smaller These results were confirmed by chronocoulometric measurements on the two types of DNA films. 

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