Page 80 - Practical book PC406-MNU-2025

MANSOURA NATIONAL UNIVERSIY
PHARM D- CLINICAL PHARMACY LEVEL II INSTRUNENTAL ANALYSIS (PC 406)

 The efficiency of chromatographic columns increases as the number of plates
becomes greater and as the plate height becomes smaller.

 Enormous differences in efficiencies are encountered in columns as a result of
differences in column type and the variation of mobile and stationary phases.

 The two parameters N and H can be calculated using the equations.

LW 2  t  2
H  , and N  16 R 
16t 2 R  W 

 A meaningful comparison of differences of two or more columns could be made by

determination of these parameters with the same compound.

The resolution of a column provides a quantitative measure of its ability to separate

two anlytes.

The significance of this term is illustrated in (Figure (3). Which consists of three

chromatograms for species A and B on three columns with different resolving

powers.

The resolution of each column is defined as.

t
t [ 2
2  Z      ]
R   R B R A
W 
s
A W B wA  w B
where all of the terms on the right side are indicated in the figure.

52 | P a g e S e c o n d s e m e s t e r 2 0 2 4 - 2 0 2 5