Metrohm 761 Compact IC - Page 148

4 Operation
761 Compact IC
138
R = (t
i+1
- t
i
) / (w
0.607i
+ w
0.607(i+1)
)
where i and i+1 indexes refer to the neighboring
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 theoretical
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 estimates
for fused or unresolved peaks, because 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 theoretical
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 component.
Total for this column includes average value for
the peaks listed.
reduced TP height, HETP/dp
The height of theoretical plate divided by parti-
cle size, called also reduced height, is calcu-
lated by formula:
H
i
= 1000 • L / (N
i
dp).
where L is length of the column in mm, dp is
particle diameter in µm.
asymmetry Peak asymmetry A
s
is calculated at
1
/10 of the
peak height as a ratio of width after the top of
the peak w
2
to the width before the top w
1
.
A
s
= w
2
/ w
1
response factor Coefficient k
1
of the calibration curve.