Velocity of mobile phase

The mixture of acetonitrile/water (1 1, v/v) was selected as most effective mobile phase. The optimum conditions for chromatography were the velocity of mobile phase utilization - 0,6 ml/min, the wave length in spectrophotometric detector - 254 nm. The linear dependence of the height of peack in chromathography from the TM concentration was observed in the range of 1-12.0 p.g/mL. 

FIGURE 7.4 (a) Plots of column back pressure against linear velocity of mobile phase (29,... 

In conventional TLC, the velocity of chromatogram development depends on the dimension of stationary-phase particles, viscosity of the mobile phase, distance from the start line of the mobile phase, and other parameters. Therefore, there is no possibility of regulation of resolution by change of migration velocity of mobile-phase flow the distance between the solvent reservoir and the solvent front (Zf) varies with time (t) according to... 

Plate height of the column as a function of the linear velocity of mobile phase The flow rate should have an optimum where the plate height is at a minimum... 

Figure 6.6 Plot of plate height [H) versus linear velocity of mobile phase (0), showing contributions from the four terms detailed above.

Linear velocity u, velocity of mobile phase through the column,... 

Linear velocity of mobile phase Optimum linear velocity of mobile phase Practical linear velocity of mobile phase Reduced velocity of the mobile phase Specific retention volume... 

Figure 4.11 Effect of mode pore diameter on flow velocity of mobile phase through monolithic capillary columns. Conditions capillary column, 100pm ID x 30cm active length stationary phase with 0.3 wt% 2-acrylamido-2-methyl-1-propanesulfonic acid mobile phase, 80 20 v/v mixture of acetonitrile and 5 mmol phosphate buffer, pH = 7. (Reprinted from [416] with permission of Wiiey Sons inc).

Remembering again not to confuse the velocity of mobile phase (in centimetres per minute) with flowrate (in millilitres per minute), it is fairly obvious that the time required for a solute to travel down a column (the retention time, is the length of the column (L) divided by the average velocity of the solute uj ... 

From the Van Deemter plot, it is clear that there exists an optimum velocity of mobile phase at which the HETP function attains its minimum. The low HETP value is favorable because it will imply a large number of theoretical plates in the column of a given length (cf. Equation 6.1). Thus, interactions between the sample and the stationary phase will favor differentiation of retention times of various analytes traversing the chromatographic column. 

The Influence of the velocity of mobile phase and sample injection volume on column efficiency for aqueous SEC is, in principle, the same as in non-aqueous SEC, Illustrated in preceding sections. Moreover, since samples are mostly ionic and several buffer solutions are used as mobile phases, a variety of phenomena might be expected. 

Velocity of Mobile Phase u. Synonymous with linear velocity. 

Linear velocity of mobile phase interstitial velocity of mobile phase Rohrschneider constant for nitromethane Mean interstitial velocity of mobile phase i.e., average linear gas velocity... 

The first moments of the enantiomers to be separated can be plotted against the inverse interstitial velocity of mobile phase and linear equilibrium constants can be readily determined from the slopes of the lines. 

The first moments of the two components of propranolol hydrochloride were plotted against the inverse superficial velocity of mobile phase in Figure 4. Straight lines were fitted to the experimental points. According to Equation 4, the equilibrium constants were determined from the slopes of the hnes, which were found to be 4.36 and 6.31 for (S)-propranolol hydrochloride and f/ j-propranolol hydrochloride, respectively. 

Figure 4. Retention time of propranolol hydrochloride versus inverse superficial velocity of mobile phase...

Fortunately the back pressure (resistance to flow presented by the packed column) is inversely proportional to the square of the column diameter. Hence, by increasing the column diameter from 4.6 to 150 mm, a pressure reduction factor of over one thousand times would be expected. However, in order to maintain a proportional linear velocity of mobile phase through the larger column, the back pressure will remain... 

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