Pulse multicyclic

With the advent of rapid-scan and high-frequency pulse methods, more direct approaches for evaluating annihilation mechanisms and dynamics have been developed. Early work of van Duyne, using triple potential steps with very short step times, allowed estimation of the annihilation rate constant for DPA anion and cation radicals [29]. More recently, Wightman and coworkers have used multicycle generation of ECL at microelectrodes to determine annihilation rate constants and ECL efficiencies [41, 42]. Figure 7 shows the normalized ECL intensity from DPA at a 1-pm Pt disk as a function of time (t/tf) at different oscillation frequencies. The intensity increases rapidly after the potential is switched, and then decays as the reactants are depleted. As the oscillation frequency is increased, the annihilation occurs closer to the electrode surface, the intensity-time profile broadens and... 

Figure 8.21 Separation of lincomycin utilizing integrated amperometry with a multicyclic pulse sequence in comparison to UV detection. Separator column Vydac C8 (208TP5451) column dimensions 150 mm x4 mm l.d. ...

The possibility of detecting sulfur-containing antibiotics such as ampicillin and lincomycin via integrated amperometry utilizing a multicyclic pulse sequence was described in Section 8.1.2.2. Dasenbrock and LaCourse [359] developed this method to determine cephapirin and ampicillin in raw milk. At... 

For the detection of sulfur-containing antibiotics such as cephapirin and am-picillin Dasenbrock et al. [26] developed multicyclic pulse sequences, which result in higher sensitivity and selectivity. In this type of pulse sequence, the potential is cycled between high and low potentials during the integration period (see... 

Fig. 7-18. Multicyclic pulse sequences for integrated amperometry of sulfur-containing antibiotics.

Fig. 7-20. Separation of lincomycin utilizing integrated amperometry with a multicyclic pulse sequence in comparison to UV detection. -Separtor column 150 mm X 4 mm i.d. Vydac C8 (208TP5451) column temperature 30°C eluant 0.1 mol/L NaOAc - acetonitrile (91 9 v/v), pH 3.75 flow rate 1 mL/min peaks (1) - (3), (5) unknown impurities, (4)...

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