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Peak Separation negative

Since in EPR we usually observe first-derivative spectra as a consequence of phase-sensitive detection (see 2.7) it is relevant to note that the first derivatives of the two distributions are features with a positive and a negative peak. The peak-to-peak separation App in field units for the two distributions is... [Pg.60]

UPD of Cu on Au(lll) electrodes in the presence of sulfate anions has been particularly intensively studied, both experimentally and theoretically [397] (for the review covering the literature up to 1995, see Ref. 398). Sulfate ions are specifically coadsorbed with underpotentially deposited Cu at negative potentials. For this system, a very striking phenomenon is the appearance of two voltammetric peaks, separated by 50-150 mV, upon addition of Cu " " ions to the H2SO4 solution [382, 397, 399-401]. For the potential range separating the peaks, the existence of adsorbate layer of the (. 3 x. 3) structure. [Pg.885]

Some experimental results [21] show that the analyte system peak is negative if it is eluted before the additive system peak and is positive if it is eluted after the additive system peak. Figure 13.8 shows the separation and indirect detection of monoglycerides on a Nucleosil-phenyl column, with water-methanol (25 75, v/v) as the mobile phase, containing 2 xlO M cholecalciferol as the additive [21]. [Pg.621]

For the separation of cations, a cation exchange column of low capacity is used in conjunction with either a conductivity detector or another type of detector. With a conductivity detector, a dilute solution of nitric acid is typically used for separation of monovalent cations, and a solution of an ethylenediammonium salt is used for separation of divalent cations. Because both of these eluents are more highly conducting than the sample cations, the sample peaks are negative relative to the background (decreasing conductivity). [Pg.5]

Substituted ferrocenes also form monoanions at very negative potentials electron addition is genuinely associated with the ferrocene nucleus rather than with an electroactive substituent. The E° value for [Fe(f/-C5H4Ph)2] is — 2.62 V, and [FeCp2] itself shows a quasi-reversible reduction at —2.93 V in dmf (452), with a peak separation of 250 mV at — 37°C(v = 1 Vsec-1). Exhaustive electrolytic reduction of ferrocene derivatives yields solutions containing the substituted cyclopentadienide anions the latter may be used in the syntheses of other cyclopentadienylmetal complexes (453). Ferrocenes are also finding use as mediators in electron-transfer reactions, especially at electrode surfaces (454-456). [Pg.70]

A reversed response pattern, with positive solute peaks before the system peak and negative ones after, is obtained when the analytes have the same charge as the probe or are uncharged. The different directions of the peaks of anionic and cationic solutes are demonstrated in the chromatogram in Figure 9, where alkylamines and alkanesulfonates are separated with naphthalene-2-sulfonate in phosphoric acid as an anionic probe 156]. [Pg.261]

When the potential was scanned to 0 mV, a pair of waves due to the redox of the azobenzene moiety appeared, in addition to that of ferrocene in the first potential scan (sohd line in Fig. 13c). The wave due to the redox of azobenzene, however, disappeared, and the redox potential and the peak separation of the redox wave due to ferrocene became more negative and smaller, respectively, in the second scan (dotted line in Fig. 13c). The redox potential and the peak separation returned to the original values after UV irradiation. These changes in the electrochemical characteristics of the latter electrode were reversible. On the basis of the structural analysis results by in situ Fourier-transform infrared reflection absorption spectroscopy (FT-IRRAS), we concluded that the electrochemical properties, that is, the redox potential and the charge transfer rate, of the ferrocene group in the SAM-modified gold electrode can be reversibly controlled... [Pg.6265]

The analysis of LSV and CV curves (today, usually computer assisted) requires electrochemical experiments free from artifacts to provide an accurate faradaic response [112]. The influence of the uncompensated solution resistance, R, (see Eq. (13)) can be greatly reduced by the use of a powerful potentiostat with fast output. However, in the common case of undercompensation of the solution resistance (e.g., in solutions with low concentration of the supporting electrolyte) the effect is the increase of the cathodic and the corresponding anodic peak separation in a manner that could be mistaken for an apparent slow rate electron transfer or the quasi-reversible regime (potentials are shifted to more negative/positive directions). [Pg.107]

The effect of decreasing equilibrium constant, K, is the shift of the current-potential curves for the reduction process to more negative potentials along with decreasing the peak current height (cf. Fig. 35). A kinetic DPP peak (responding to the reduction of free metal ions) is always small (in comparison to the reduction peak of the parent metal complex). The peak current ratio Ip+/Ip of the metal complex tends to be 1.29. The positive/negative peak separation is nearly 10 mV which is the same value as the peak amplitude AE. This exactly fits the criterion for a CrevE mechanism in DPP. [Pg.221]


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Negative peaks

Peak Separation

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