Zero retention time

At a flow rate of 1 ml min the zero retention time on the analytical column is ... 

Note that the initial slope of the adsorption isotherm can be easily obtained from the knowledge of the retention time associated to a small injection performed on a column, as this retention time is given by tR = t0 ji + 1 - -k where /0 = V/Q is tiie zero-retention time based on the external bed porosity e (commonly, e is about 0.36-0.4). 

The zero retention time t0 for mobile phase or other unretained molecules to move from one end of the column to the other can be determined as follows ... 

The problem of determining V-j in SEC is similar to that of determining zero retention time (tg) in other liquid chromatography columns. Recently, there have been several papers dealing with the determination of retention time of a retained peak in HPLC (12-19). In high-performance reversed-phase chromatography, McCormick and Karger (1 ) and Berendsen, et al., (16) have employed D2O to measure tg. Neidhart et al.,... 

Figure 6 shows a chromatogram for linear elution chromatography. The amount of probe injected is set to the amount corresponds to the limit of sensitivity of the detector. The retention time, tR, is the time that the average molecule of probe takes to travel the length of column. And the time is measured to be the midpoint of the symmetrical curve for nonpolar probes and to be a position at which the total area of the asymmetrical curve for polar probes is divided into equal areas. The time, to, is the zero retention time reference measured with a non adsorbing probe such as methane simply to pass through the column space from inlet to out let. 

Assuming an external porosity of 0.4 for the laboratory column, the zero retention time associated to the pulse test is... 

To check the quality of the columns of the SMB pilot plant, a pulse test is performed on all the columns connected in series, the eluent flow rate being fixed to 4 liters/h. The total bed volume of the pilot plant being 2.016 liters, assuming an external porosity of 0.4, the zero retention time associated to... 

Fig. 3.16. In MEKC, neutral analytes pass the detection window at their retention time t/ , which is between the zero retention time of the bulk flow tQ and the retention time of the...

One way to optimise a separation is by changing the composition of the aqueous mobile phase. For example, the pH of the buffer can be varied. This can have dramatic effects on the EOF and therefore change the zero retention time to. The charge of the micelles might also be altered by a change in pH, resulting in a different tmc- Furthermore, the degree of the ionisation of the analytes and the electrolyte system depends on the pH. This influences both the capacity factor k and the selectivity factor a. 

The bed voidage can be evaluated from the zero retention time of a non-adsorbed component to the stationary phase. For a component which enters the pore system but does not adsorb on the surface of the stationary phase, the retention time of such a component is given by ... 

The zero retention time of TTBB was given by Equation 1. From the plot of mean retention time against the inverse flow rate in Figure 3, the total porosity Ex was found to be 0.64. From Equation 2, the bed voidage was found to be 0.34 for the column. 

Locate the time when the upper interface (between the supernatant liquid and slurry) is at height Z g, halfway between the initial height, Zg, and the extrapolated zero-time compression zone height, Z g. This time represents the period in which all the solids were at the critical dilution and went into compression. The retention time is computed as t -1,., where t is the time when the solids reach the specified... 

In Fig. 34.34 the first three local PCs with the associated eigenvalues are given for four retention time regions (a) a zero component region (Fig. 34.34a), (b) selective chromatographic regions at the up-slope side (Fig. 34.34b), (c) and at the... 

Experiment A is a non-adsorption experiment through the core, performed to measure the time for emergence of the peak. A 1.3% (concentration higher than the standard) acidified brine is loaded into the sample loop to be used as a sample medium. This particular experiment is carried out to measure the retention time by recording the time required before the peak is observed. The retention time can also be used to compute the exact porosity of the core, under the assumption of zero adsorption of salts from the brine. 

This is a disaster. There is little or no separation, and almost everything is eluting from the column immediately at a k little more than zero. The first step is to increase the retention times of all the solutes, ie increase the k values. 

Zero Data system Location of the x-axis for the plotted chromatogram Changes appearance of chromatogram Does not change peak recognition, retention time, area or width Does not affect the raw data... 

We also vary the sample size (from 1 to 2 y ) between runs at a given P and T. This allows extrapolation of peak areas to zero sample size as shown in Figure 4. The flow rate within the column must be constant for an isotherm. We record the following parameters ambient pressure and temperature, inlet pressure, outlet pressure, column temperature, retention time for both air and water, water peak area, ambient flow rate, regulator pressure, sample sizes, detector current and temperature, injector temperature, and attenuation. 

As would be expected, the smaller the feed particle size, the greater the surface area per given weight is available for bonding to the ytterbium ions, hence the greater the concentration of marker. The greatest concentration of ytterbium in faecal DM occurred after approximately 24 h, with the concentration approximately zero after 75 h the mean retention time was 26.07 h. The maximum ranges for the concentration of ytterbium in the faecal DM after approximately 24 h was approximately as follows ... 

The ethyl acetate phases of 8 hrs and NADH-FAD-mannitol samples were inspected by gas-liquid chromatography analysis for detection of metabolites (hydroxylated and/or carboxylated) by treatment with TMS-derivatization agent or diazomethane. By comparing the spectra of all cofactor-treated samples to zero time control and autoclaved 8 hrs control spectra, 6 possible metabolic products were indicated and retention times noted (Table 7). 

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