Agilent Technologies 1290 Infinity II 2D-LC User Manual page 370

14 Theoretical Background
Theoretical basis of 2D-LC
From the pracitcal point of view the performance between 1D- and 2D-LC should
be compared, considering the following aspects:
•
•
2
Ideal D Peak One major problem in 2D-LC is loss of
Capacity The determining factors are:
•
•
2
A
chromatograms obtained on the second column and the second column and
detector are just a unique type of chemically selective detector of what comes
out of the first column (see,
observed on the second column is independent of the sampling time used in the
1
D.
This leads to two extreme scenarios, on how mixtures of components may
behave:
•
•
The theoretical limits for ideal
NOTE
Murphy-Schure-Foley Criterion (M-S-F sampling criterion). According to this
criterion, the effluent must be sampled at least 3 – 4 times over 8 width of the
first dimension peak.
2D-LC User Guide
Peak capacity
Number of peaks observed in experimental chromatograms
2
Gradient time of the
1
D separation
Resolution of a pair of peaks in the two-dimensional space is related to the
resolution on the first and second dimensions as the Pythagorean average
(see Figure 172 on page 366)
D chromatogram is only a way of displaying a lengthy series of sequential
Unresolved mixture is injected into second column and second column
separates analytes perfectly
R is independent of
s,2D
Partially resolved mixture is injected into second column and analytes
co-elute on the second column
R strongly depends on first dimension sampling rate.
s,2D
This indicates, that it's very important to respect, how often the
must be sampled to avoid loss of resolution.
1
D resolution due to
D separation cannot exceed the sampling interval of the
"2D as detector" on page 371). The peak width
1
D sampling rate
2
D peak capacity are defined by the
2
D sampling process.
1
D effluent
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