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| | 49 year old Director (Film, Tv, Radio) Lincourt from Val-Belair, likes to spend some time metal detecting, [http://ganhedinheironainternet.comoganhardinheiro101.com/ como ganhar dinheiro] na internet and cloud watching. In the last few months has gone to locations such as Historic Monuments of Dengfeng in “The Centre of Heaven and Earth”. |
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| '''Retention uniformity''', or ''R<sub>U</sub>'', 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 function]]s.
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| ==Formula==
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| Retention uniformity is calculated from the following formula:
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| <math>
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| R_{U} = 1 - \sqrt{\frac{6(n+1)}{n(2n+1)}\sum_{i=1}^{n}{\left(R_{Fi}-\frac{i}{n+1}\right)^2}}
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| </math>
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| where ''n'' is the number of compounds separated, ''R<sub>f (1...n)</sub>'' are the [[Retention factor]] of the compounds sorted in non-descending order.
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| == Theoretical considerations ==
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| The coefficient lies always in range <0,1> and 0 indicates worst case of separation (all R<sub>f</sub> values equal to 0 or 1), value 1 indicates ideal equal-spreading of the spots, for example (0.25,0.5,0.75) for three solutes, or (0.2,0.4,0.6,0.8) for four solutes.
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| This coefficient was proposed as an alternative to earlier approaches, such as ''D'' (separation response), ''I<sub>p</sub>'' (performance index) or ''S<sub>m</sub>'' (informational entropy). Besides its stable range, the advantage is a stable distribution as a random variable, regardless of compounds investigated.
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| In contrast to the similar concept called [[Retention distance]], ''R<sub>u</sub>'' is insensitive to ''R<sub>f</sub>'' values close to 0 or 1, or close to themselves. If two values are not separated, it still indicates some ''uniformity'' of chromatographic system. For example the ''R<sub>f</sub>'' values (0,0.2,0.2,0.3) (two compounds not separated at 0.2 and one at the start ) result in ''R<sub>U</sub>'' equal to 0.3609.
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| == See also ==
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| * [[Chromatographic response function]]
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| ==References==
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| * Komsta Ł., Markowski W., Misztal G., A proposal for new R<sub>F</sub> equal-spread criteria with stable distribution parameters as a random variable. J. Planar Chromatogr. 2007 (20) 27-37.
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| [[Category:Chromatography]]
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49 year old Director (Film, Tv, Radio) Lincourt from Val-Belair, likes to spend some time metal detecting, como ganhar dinheiro na internet and cloud watching. In the last few months has gone to locations such as Historic Monuments of Dengfeng in “The Centre of Heaven and Earth”.