Concentration at peak maximum

The band broadening and the analyte dilution resulting from extracolumn band broadening were compared between the microfluidic chip system and the conventional macro-scale system. For a proper comparison, we calculated the analyte concentration at the peak maximum of the bioactive peaks (Cmax) from E-64 injections in both systems. It turned out that the dilution factor when comparing the concentration at peak maximum with the injected concentration was only 10% higher for the microfluidic chip system in comparison to the conventional macro-scale system. 

Regarding quantification with concentration sensitive detectors (DAD, ELD, etc.), decrease of the peak area. Due to the increase in flow the components elute at a lower elution strength, the peak volume increases, thereby the dilution too, the concentration at peak maximum decreases. 

Figure 11.6 shows adsorption isotherms for RB and RllO, which are obtained by plotting the square root of the SH intensities at peak maximum against the bulk concentrations of the dyes. These isotherms can be fitted well by a Langmuir adsorption isotherm, and the adsorption constants for RB and R110 are estimated as 4.9 X 10 M and 4.4 x 10 M , respectively. The difference in the adsorption constant between RB... 

The peak represented 3 pm of material and, taking the concentration at the peak maximum as twice the peak average concentration, the peak maximum concentration was about 8 pm/ml. The peak height appears to be about three times the noise and so the sensitivity (that concentration that will give a signal equivalent to twice the noise) is about 5.3 pm/ml or in more standard terms 5.3 x 10 g/ml. As the chiral detector is a bulk property detector, a sensitivity of 5.3 x 10 g/ml seems more realistic. Nevertheless, this sensitivity is a great improvement on many chiral detectors previously described. 

A possibility to reduce the influence of column efficiency on the results obtained by the ECP method is to detect the position of the peak maximum only, which is called the peak-maximum or retention-time method. Graphs like Fig. 6.23 are then achieved by a series of pulse injections with different sample concentrations. The concentration and position of the maximum is strongly influenced by the adsorption equilibrium due to the compressive nature of either the front or the rear of the peak (Chapter 2.2.3). Thus, the obtained values are less sensitive to kinetic effects than in the case of the ECP method. The isotherm parameters can be evaluated in the same way as described in Section 6.5.7.6, but the same limitations have to be kept in mind. For some isotherm equations, analytical solutions of the ideal model can be used to replace the concentration at the maximum (Golshan-Shirazi and Guiochon, 1989 and Guiochon et al., 1994b). Thus, only retention times must be considered and detector calibration can be omitted in these cases. 

Where is the concentration of the constituent at peak maximum of the dispersed zone. When fluid elements on the rising or falling slopes of the concentration gradient of the dispersed zone are concerned, the equation is expressed as ... 

The concentration of solute at the peak maximum is approximately twice the average... 

The Freundlich liquid phase isotherm can be used to determine the effect of solubility on the adsorptive capacity of activated carbon over a range of different concentrations. Phenol is highly soluble due to its polar nature whilst, in comparison, tetrachloroethylene (PCE) has a low solubility due to being non-polar. In the isotherms illustrated, the concentration of phenol is low relative to its solubility limit and consequently, the adsorptive capacity peaks at 18% maximum (see Figure 9). In comparison the concentration of tetrachloroethylene is relatively close to its solubility limit and, accordingly, the adsorptive capacity is exceptionally good. 

The peak volume is directly proportional to the square of the column diameter and the column length and decreases with Increasing column efficiency (decreases for smaller particle packings). The concentration at the peak maximum, C—, is given by... 

Modifiers can be used very effectively in on-line SFE-GC to determine the concentration levels of the respective analytes. This presents an advantage in terms of the use of modifiers in SFE, since they appear as solvent peaks in GC separations and do not interfere with the target analyte determination. Although online SFE-GC is a simple technique, its applicability to real-life samples is limited compared to off-line SFE-GC. As a result, on-line SFE-GC requires suitable sample selection and appropriate setting of extraction conditions. If the goal is to determine the profile or matrix composition of a sample, it is required to use the fluid at the maximum solubility. For trace analysis it is best to choose a condition that separates the analytes from the matrix without interference. However, present SFE-GC techniques are not useful for samples... 

For each of the model compounds, some material will have leached deeper Into the soil than Is shown in the table. The model calculates only the position of maximum concentration. For a compound like DBCP, which has a very weak adsorption interaction with the soil, the concentration profile will be spread out. DBCP would probably be found at low concentrations at the 1017 cm level. For the strongly adsorbed compounds, such as toxaphene and methoxychlor, the concentration peak will be narrow, and the depth of maximum concentration is the depth where most of the material is. 

Equation (8.44) helps explain why the concentration profile in Figure 8.20 contains a maximum. Before the peak, and at short times, the second term on the right-hand side of Equation (8.44) is tiny because [B] is small. Therefore, the net rate d[B]/dt is positive, meaning that the concentration of B increases. Later - after the peak maximum - much of the [A] has been consumed,... 

The shape of the curve obtained at -78 °C was the same for all the solvents and shows a steep rise in the DP with increasing monomer concentration up to a maximum at a relatively low monomer concentration, followed by a more gradual fall to the DP characteristic of polymers obtained from undiluted monomer. The monomer concentration at which the DP maximum occurs varied from one solvent to another, as did the height of the DP peak. 

The increase in the anion concentration results in higher values of Cj at the maximum and in the shift of the maximum toward the zero charge density. The shift of the peak with increasing concentration is caused by the screening effect of the anions, accumulated in the diffuse layer and linked to the positive ends of the solvent dipoles. However, the changes in the shape of the C, vs. plots are greater on the negative than on the... 

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