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15 Cards in this Set
- Front
- Back
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h
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peak height
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L
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column length
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W(b)
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peak width at base
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W(1/2)
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peak width at half height (only for on-scale peaks)
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t(R)
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absolute retention time
the time from injection to peak elution |
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t(0)
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dead time
time between injection and first little peak; amount of time the compound spends in the mobile phase; dead volume of the column. |
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t(R')
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adjusted retention time
amount of time analyte spends in the stationary phase t(R') = t(R) - t(0) |
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k'
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capacity factor
where the peak elutes relative to the dead time (t(0)). k' represents a better measure of retention than t(R). k' = t(R')/t(0) |
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α
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separation factor
where the peaks elutes relative to each other α = k'(2)/k'(1) α may be changed by altering the column or the mobile phase (retention factor). Neither α nor k' take into account dispersion effects, unlike plate number (N--see other card) |
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N
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plate number a.k.a. column efficiency
measure of peak narrowness; columns with larger N values (and hence smaller plates) give generally better separations N can be determined by any of the following 3 formulae: 5.54 (t(R)/W(1/2))^2 16 (t(R)/W(b))^2 2π(t(R)h/A)^2 |
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H
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Height equivalent to a theoretical plate (HETP)
The number of theoretical plates in a column. H decreases (plates get smaller, and hence more numerous), as the resolving power of the column increases. H = L/N |
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A(s)
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asymmetry factor
A(s) = W(10%) (b) /W(10%) (a) |
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R(s)
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resolution
The degree of separation of adjacent peaks. Baseline separation of adjacent peaks occurs when R(s) > 1.5 R(s) = t(R1) - t(R2)/0.5 (W(1) + W(2)) OR (√ ̅ N/4) • ((α-1)/α) • (k'/(k'+1)) |
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retention factor
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((α-1)/α)
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selectivity
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(k'/(k'+1))
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