Lecture 15 Chromatography Introduction and Plumbing Harris Ch. 23

Time = t m “Dead time”

Time = t m “Dead time” No separation! time

Time for solvent molecule is the same as before: t m Time for analyte molecule is different: t r Retention time time Adjusted retention time: trtr tmtm t’ r Stationary phase Mobile phase

Retention factor: Time in mobile phase Time in stationary phase If you have many molecules or Distribution coefficient

Time for solvent molecule is the same as before: t m Time for analyte molecules is different: t r (1) and t r (2) time trtr tmtm t’ r (1) Stationary phase Mobile phase t’ r (2) Selectivity factor Separation factor Relative retention

Retention factor k : Distribution coefficient Separation factor:

Number of theoretical plates: W = 4  L - length of column Height of theoretical plate is: H = L / N = L   2 / t r 2 Plate Number Plate Height

Zone broadening: The van Deemter equation H - plate height u - flow rate

A = 0

B

van Deemter plot