Split peaks

Most flow injection analyses use peak height as the analytical signal. When there is insufficient time for reagents to merge with the sample, the result is a split-peak, or doublet, due to reaction at the sample s leading and trailing edges. This experiment describes how the difference between the peak times can be used for quantitative work. 

For cell isolation purposes an important cytometer sort feature is pulse-pileup also referred to as peak-pileup or PPU. This recognizes split peak intensities arising from two or more cells in the same droplet that are strung together in chains or that coincidentally partially eclipse the laser beam. The two split peaks would each have the same forward- and side-scatter... 

No, that is not all. You can tell that the —CH2— protons and the —CH3 protons split each other by their coupling constant, the distance between the split peaks of a single group. Coupling constants are called J values, and are usually given in hertz (Hz). You can read them right from the chart, which has a grid calibrated in hertz. If you find protons at different chemical shifts... 

What causes NMR peaks to be split into doublets, triplets, etc. How does the presence of split peaks assist with qualitative analysis ... 

In addition, the split peaks can be used for estimation of electron-transfer coefficient as well as for precise determination of the formal potential of the surface electrode reaction. The potential separation between split peaks is insensitive to the electron-transfer coefficient. However, the relative ratio of the heights of the split peaks depends on the electron-transfer coefficient according to the following function ... 

With respect to the formal potential of the surface electrode reaction, Figs. 2.45c and 2.46 show that the split peaks are symmetrically located around the formal potential, which enables precise determination of this important thermodynamic parameter. 

Table 2.5 Critical values of the SW amplitude and corresponding potential separations of the split peaks for various values of the electrode kinetic parameter. Conditions of the simulations are the same as for Fig. 2.41...

Similar to the pure surface electrode reaction, the response of reaction (2.146) is characterized by splitting of the net peak under appropriate conditions. The splitting occurs for an electrochemically quasireversible reaction and vanishes for the pure reversible reaction. Typical regions where the splitting emerges are 3 < m < 10 and 0.1 < r < 10 for a = 0.5 and i sw = 50 mV. Contrary to the surface electrode reaction where the ratio of the split peak currents is solely sensitive to a, in the present system this ratio depends additionally on r. For instance, if a = 0.5 and r = 1 the ratio is = 1 for r = 10, > 1 and r = 0.1, < 1. Finally it is worth mentioning when experimentally possible, the electrode mechanism represented by (2.145) to (2.147) has to be simplified to a simple surface reaction (Sect. 2.5.1) in order to avoid the complexity arising from the effect of diffusion mass transport. 

Figure 2.96 shows the splitting of the net peak under increasing of the dimensionless electrode kinetic parameter for a given film thickness. The potential separation between split peaks increases in proportion to the electrode kinetic parameter and the amplitude of the potential modulation. The dependence of the peak potential separation on the amplitude is separately illustrated in Fig. 2.97. The analysis of the splitting by varying the amplitude is particularly appeahng, since this instrumental parameter affects solely the split peak without altering the film thickness parameter. Table 2.7 lists the critical intervals of the film thickness and the electrode kinetic parameters attributed with the splitting.

Similar to the surface electrode processes (Chap. 2.5.1) the peak current ratio of the split peaks ( fp,c/ lp,a) is a function of the electron transfer coefficient o. Note that the anodic and the cathodic peak is located at the more negative and more positive potentials, respectively. This type of dependence is given in Fig. 2.98. Over the interval 0.3 < < 0.7 the dependence vs. is hnear, associated with the... 

The gold(I) precursor Au(02CNEt2)(PPh3) reacts with a silica surface previously dehydroxylated at 160 °C to yield monopodal isolated Au(l) grafted moieties [(=SiO) Au(PPh)3], as indicated by the single-component ArLm7/2) spin-orbit split peak in... 

Fig. 9 Temperature dependence of the local structure of PMN described by the pulsed neutron PDF. The upper inset shows the PDF at 650 K measured (circles) and calculated from the crystal structure data (line). At low temperatures the peak at 2.45 A shows local off-centering of Pb " ion, and the split peak at 3.33 and 3.63 A suggest that the direction of off-centering is along [10 0] [18]...

RPC separations of ionic samples usually require ionic additives to the mobile phase, which may cause problems in HPLC/MS operations. Completely ionized solutes are much less retained than the corresponding uncharged species and elute close to the column hold-up volume, often as asymmetric or even split peaks. Weak acids are eluted in order of decreasing constants and weak bases... 

Hage, D.S., Walters, R.R., and Hethcote, H.W., Split-peak affinity chromatographic studies of the immobilization-dependent adsorption kinetics of protein A, Anal. Chem., 58, 274-279, 1986. 

Fig. 28. Asymmetry of quadrupole split peaks due to the Gol danskii-Karyagin effect. 7t = +j - transition a — i - i transition c = (27t/7)2( - <.x2 . z and x are parallel and perpendicular, respectively to the surface normal. Figure according to Suzdalev and Makarov (208).

When the composition of MeCN in the reaction medium was increased, the resulting mixture showed decreasing analyte sensitivity, usually accompanied by broad tailing and split peaks. Acetonitrile significantly suppressed the derivatization reaction between /3-lactam and mercury chloride. Thus, it must be partially evaporated prior to derivatization (83), or the reaction time should be prolonged up to 180 min for the determination of OXA, CLO, and DICL (86). 

The present method recommended by this major industrial account is to disconnect the center-voided column, grasp it in one hand, and rap the counter with it twice, reverse the column, and do the same with the other end. Obviously, not hard enough to bend the column Hook it up backwards and run it at high flow rate for a minute or two. Then run the four-standard mixture. The column is run reversed from then on. It is possible that an end void may be formed yielding rabbit-eared split peaks, and must be repacked, but the column bed should be restored. 

---