A separation in which the mobile phase composition remains constant throughout the procedure is termed isocratic(meaning constant composition). The word was coined by Csaba Horvath who was one of the pioneers of HPLC.[citation needed],
The mobile phase composition does not have to remain constant. A separation in which the mobile phase composition is changed during the separation process is described as a gradient elution.[3] One example is a gradient starting at 10% methanol and ending at 90% methanol after 20 minutes. The two components of the mobile phase are typically termed "A" and "B"; A is the "weak" solvent which allows the solute to elute only slowly, while B is the "strong" solvent which rapidly elutes the solutes from the column. In reverse-phase chromatography, solvent Ais often water or an aqueous buffer, while B is an organic solvent miscible with water, such as acetonitrile, methanol, THF, or isopropanol.
In isocratic elution, peak width increases with retention time linearly according to the equation for N, the number of theoretical plates. This leads to the disadvantage that late-eluting peaks get very flat and broad. Their shape and width may keep them from being recognized as peaks.
Gradient elution decreases the retention of the later-eluting components so that they elute faster, giving narrower (and taller) peaks for most components. This also improves the peak shape for tailed peaks, as the increasing concentration of the organic eluent pushes the tailing part of a peak forward. This also increases the peak height (the peak looks "sharper"), which is important in trace analysis. The gradient program may include sudden "step" increases in the percentage of the organic component, or different slopes at different times - all according to the desire for optimum separation in minimum time.
In isocratic elution, the selectivity does not change if the column dimensions (length and inner diameter) change - that is, the peaks elute in the same order. In gradient elution, the elution order may change as the dimensions or flow rate change.[citation needed]
The driving force in reversed phase chromatography originates in the high order of the water structure. The role of the organic component of the mobile phase is to reduce this high order and thus reduce the retarding strength of the aqueous component.
Using isocratic retention parameters, the gradient elution retention time for several proteins has been calculated. The gradient retention time calculation is based on fitting the isocratic retention data to an equation of the form: log k′ = m log (1/[Ca2+]) + log K and on applying well-established principles of gradient elution. A good correlation between the observed and calculated retention times for several test proteins was obtained at various total gradient times and column flow-rates.Conversely, isocratic retention parameters characterizing protein retention can be calculated from gradient elution retention data. However, even with retention data of high quality, small errors are amplified by the log-log nature of the ion-exchange isocratic retention model employed.Based on the close correlation between predicted and observed gradient retention times, no evidence for protein denaturation resulting from immobilization of the protein at high initial k′ values at or near the column inlet was observed.
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concentration gradient
Concentration gradient. After there's no concentration gradient, equilibrium occurs, which means no more diffusion.
oxidative phosphorylation does not involve with the respiratory complex in the inner mitochondria membrane. Oxidative phosphorylation useful in generate the production of ATP from the proton gradient or proton motive force. Chemiosmotic coupling invilve the manner of ETC on how its create the proton gradient and the proton gradient is indirectly directed with the production of ATP.The proton gradient causes the conformational change of tigthly binding of ATP to open binding ATP .Then ATP can be released and be used to the metabolic cell needs and translocate the ATP to cytoplasm that can be used to phosphorylate substrate.
in isocretic system we use only single mobile phase but in gredent system we use two or more mobile phases.
Using isocratic retention parameters, the gradient elution retention time for several proteins has been calculated. The gradient retention time calculation is based on fitting the isocratic retention data to an equation of the form: log k′ = m log (1/[Ca2+]) + log K and on applying well-established principles of gradient elution. A good correlation between the observed and calculated retention times for several test proteins was obtained at various total gradient times and column flow-rates.Conversely, isocratic retention parameters characterizing protein retention can be calculated from gradient elution retention data. However, even with retention data of high quality, small errors are amplified by the log-log nature of the ion-exchange isocratic retention model employed.Based on the close correlation between predicted and observed gradient retention times, no evidence for protein denaturation resulting from immobilization of the protein at high initial k′ values at or near the column inlet was observed.
noThe correct answer if you are dealing with cells is concentration gradient
A concentration gradient forms when there is a difference in concentration between one place and another.
Yes
gradient
Concentration Gradient
if you are doing isocratic elution nothing will change at all but in case pf gradient analysis elution order may change.
pressure gradient
Pressure gradient is the rate of pressure change as you change position, not just the difference between the lowest pressure and the highest pressure, but how great (or small) the physical distance between them. Since it the pressure difference that make air flow (wind) the greater the pressure gradient, the greater the wind.
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pressure gradient