Tailing peaks reduction

Coreduction of Au and Pt ions by refluxing alcohol in the presence of PVP gives the colloidal dispersions of Au-core/Pt-shell structured bimetallic nanoparticles, as mentioned before. The formation of this bimetallic nanoparticles was traced by in situ UV-Vis spectra (68). The spectral change is shown in Figure 9.1.15, in which the peaks ascertained to be the metal ions disappear at first, and then the broad tailing peaks due to the colloidal dispersions appear. More precisely speaking, the tetrachloroauric(III) acid (at —320 nm) is reduced first, followed by reduction of hexachloroplatinic(IV) acid (at —265 nm). This order of reduction is consistent with the standard redox potential of the two metal ions. After the reduction of two... 

The conditions for Pu reduction and elution were examined in detail, and a variety of reducing agents were tested.82 A flow system with an on-line scintillation detector was used to show the elution behavior in detail under well-controlled flow conditions. It was found that reduction and elution with hydroquinone was slow, resulting in broad tailing peaks and incomplete reduction. Some Pu remained in the Pu(IV) state and could be eluted with a complexant on completion of the reductant/HCl elution step. However, by choosing other reductants, rapid reduction and clean elution as a sharp peak could be obtained. These results are shown in Figure 9.14. 

The Ti02 support and the 6Nb/Ti catalyst undergo a very poor reduction compared to that occurring when vanadium is present in the catalyst. The Ti02 support shows a tailed peak with maximum at 554 C while the addition of niobium oxide results in the appearance of a new peak at 609°C. 

Fig. 18b.9. Example cychc voltammograms due to (a) multi-electron transfer redox reaction two-step reduction of methyl viologen MV2++e = MV++e = MV. (b) ferrocene confined as covalently attached surface-modified electroactive species—peaks show no diffusion tail, (c) follow-up chemical reaction A and C are electroactive, C is produced from B through irreversible chemical conversion of B, and (d) electrocatalysis of hydrogen peroxide decomposition by phosphomolybdic acid adsorbed on a graphite electrode.

Tailing of peaks, 38.67.82 reduction by ammes. 67. reduction treatment with buffers, 67 Tailing reducers, 118 Taitrazine. 230, 249, 265 Tenqrerature of column, 192 el on modulator distribution, 85,93, 96... 

The trifluoroacetates of 1-hexanol and 1-heptanol had retention times of 3.0 and 5.1 minutes, respectively, on Carbowax at 80°C. The trifluoroacetates of 1-undecanol, nonane-1,9-diol, and decane-1,10-diol had retention times of 4.0, 5.1, and 7.6 minutes on Apiezon at 170°C. Peaks were well formed and did not have the characteristic tail of alcohol peaks. The reduction-trifluoroacetylation treatment of 5-ketohexanoic... 

The third term of Equation 2.80 accounts for resistance to mass transfer in liquid phase. An obvious way of reducing this term is to reduce the liquid film thickness d. This causes a reduction in k and an increase in the term k1/(1 + k )2- However, using thinly coated column packings increases the probability of adsorption of solute molecules on the surface of support material, which might result in peaks tailing. 

The problem that reduction of the plate heights will not considerably improve the peak shapes on MIP phases has perhaps not been recognized immediately when MIP CEC was developed. A recent (2006) review by Ch. Nilsson and S. Nilsson [13] concludes, however So far all verified imprint-based CEC separations showed peak tailing, due to polydispersity of the imprinted receptor sites, resulting in different affinity and poor mass transfer. Although we do not agree with the exact wording (because the isotherm may be nonlinear even if all sites are the same... 

This chemical hysteresis will, of course, affect radionuclide transport. For example, if hysteresis occurs during a column experiment in which a pulse of tracer is added to the influent, the effluent curve will show heavy tailing and a reduction in peak concentration. Ignoring hysteresis effects could cause serious errors in predicting radionuclide movement. 

Microsomal reduction of chromium(VI) can also result in the formation of chromium(V), which involves a one-electron transfer from the microsomal electron-transport cytochrome P450 system in rats. The chromium(V) complexes are characterized as labile and reactive. These chromium(V) intermediates persist for 1 hour in vitro, making them likely to interact with deoxyribonucleic acid (DNA), which may eventually lead to cancer (Jennette 1982). Because chromium(V) complexes are labile and reactive, detection of chromium(V) after in vivo exposure to chromium(VI) was difficult in the past. More recently, Liu et al. (1994) have demonstrated that chromium(V) is formed in vivo by using low-frequency electron paramagnetic resonance (EPR) spectroscopy on whole mice. In mice injected with sodium dichromate(VI) intravenously into the tail vein, maximum levels of chromium(V) were detected within 10 minutes and declined slowly with a life time of about 37 minutes. The time to reach peak in vivo levels of chromium(V) decreased in a linear manner as the administered dose levels of sodium... 

If the sample size and thus the nonlinearity is not extreme, then neither is the tailing. Modest tailing is common in chromatographic peaks. The reduction of solute load is frequently a cure for tailing. 

Reduction of 9-substituted anthracenes, (91), leads to radical anions, which, because of the electron-withdrawing substituents, are quite stable with respect to protonation and cleavage in aprotic solvents. In polar aprotic solvents the radical anions exclusively dimerize, and the reaction has been the subject of a number of studies [247-258]. The products are the tail-to-tail dimeric dianions as in Eq. (57), which are fairly stable. In CV the dimer dianions can be detected as a new oxidation peak on the reverse scan at a potential several hundred millivolts anodic relative to the potential of radical anion formation. On preparative or semipreparative scales the dimer dianion has in a single case been detected by H-NMR [249], and oxidative electrolysis of the dimer dianions in most cases restores the starting material. 

Figure 1. A comparison of the band shape obtained with a conventional "micro" TCD and a systematically designed small volume cell. Note the improvement both in width and the reduction in "tailing". (Methane peak, digitized data) Reproduced, with permission, from Ref. 1. Copyright 1977, Journal of Chromatographic Science,...

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