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In chromatography, the retardation factor (R) is the fraction of an analyte in the mobile phase of a chromatographic system. [1] In planar chromatography in particular, the retardation factor R F is defined as the ratio of the distance traveled by the center of a spot to the distance traveled by the solvent front. [ 2 ]
Retention distance, or R D, is a concept in thin layer chromatography, designed for quantitative measurement of equal-spreading of the spots on the chromatographic plate and one of the Chromatographic response functions. It is calculated from the following formula:
For example, if a compound travels 9.9 cm and the solvent front travels 12.7 cm, the R ƒ value = (9.9/12.7) = 0.779 or 0.78. R ƒ value depends on temperature and the solvent used in experiment, so several solvents offer several R ƒ values for the same mixture of compound. A solvent in chromatography is the liquid the paper is placed in, and ...
This factor is defined in terms of a ratio of the retention factors of a pair of neighboring chromatogram peaks, and may also be corrected for by the void volume of the column. The greater the separation factor value is over 1.0, the better the separation, until about 2.0 beyond which an HPLC method is probably not needed for separation.
The [N 1/2 /4] term is the column factor, the [(α-1)/α] term is the thermodynamic factor, and the [k 2 '/(1+k 2 ')] term is the retention factor. The 3 factors are not completely independent, but they are very close, and can be treated as such. So what does this mean?
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A common solvent system is a mixture of hexane and ethyl acetate, with proportions adjusted until the target compound has a retention factor of 0.2 - 0.3. Contrary to common misconception, methanol alone can be used as an eluent for highly polar compounds, and does not dissolve silica gel. There is an optimum flow rate for each particular ...
Net retention rate, or NRR, was 111% in the third quarter. DPS licensing model continues to gain traction and adoption. We now have almost 1,500 customers globally, representing more than 35% of ...