Metrohm IC Net 2.2 - Manual (Page 192)

7 Methods
IC Net 2.2 184
where i and i+1 indexes refer to the neigh-
boring peaks, and w
0.607
stands for the peak
width at 60.7 % of the peak height.
effectivity, TP Effectivity for the peak in number of theo-
retical plates. The number of theoretical
plates N
i
per column for a chosen peak is
calculated for a chromatographic peak by
one of two formulas:
N
i
= 2 PI (t
i
• H
i
/ A
i
) 2 ,
where PI = 3.1415926..., t
i
= retention
time, H
i
= height, A
i
= area of the peak.
The more commonly used formula is:
N
i
= 5.54 (t
i
/ w
i
) 2 ,
where w
i
is the width on the half-height of
the peak. The first formula offers better es-
timates for fused or unresolved peaks, be-
cause the half-width errors for those peaks
are much greater than height or area errors.
Total for this column includes average value
for the peaks listed.
effectivity, TP/m Effectivity for the peak in number of theo-
retical plates per meter. The number of
theoretical plates per meter N' for the given
component is calculated as:
N' = N
i
• 1000 / L,
where L is length of the column in mm and
N
i
is effectivity of the column for i-th com-
ponent.
Total for this column includes average value
for the peaks listed.
reduced TP height, HETP/dp
The height of theoretical plate divided by
particle size, called also reduced height, is
calculated by formula:
H
i
= 1000
•
L / (N
i
dp).
where L is length of the column in mm, dp
is particle diameter in
µ m.
gaussian factor The Peak gaussian factor PGF is the ratio
of the width at half peak height w
1/2
to the
width at 1 /
10
peak height w
1/10
multiplied with
the reciprocal value of this ratio for an ideal
gaussian peak shape.
PGF = 1.83 • w
1/2
/ w
1/10