Software Manual

7 | Evaluating Results
252 | NGC Chromatography Systems and ChromLab Software
Traces
You can choose to analyze the column’s
performance based on either a single UV trace or
the conductivity trace.
Calculate
You can calculate and display the following
measurements:
Number of plates (N) — displays the number of
theor
etical plates, an indication of column
ef
ficiency. Theoretical plate numbers are an
indirect measure of peak width for a peak at a
specific time retention. Columns with high plate
numbers are considered to be more efficient. The
formula used to calculate number of plates is:
N = 5.54 * (peak retention time/peak width at half
height)
2
Plates per meter (N/L) — the number of
theoretical plates per meter, a value used to compare theoretical plate numbers
between columns. This measurement requires the medium bed height (in cm) for the
column in use. The formula used to calculate plates per meter is:
plates/meter = N/L
where L = medium bed height
Height equivalent to theoretical plate (HETP) — the height equivalent to a
theor
etical plate, a value used to determine the number of theor
etical plates
contained in any length of column. Shorter plate heights indicate more efficient
columns. This measurement requires the medium bed height. The formula used to
calculate HETP is:
HETP = L/N