The quality of a chromatographic separation is described in principal by different
parameters. A first criterion for a good chromatography is the shape of the peak. It
should be symmetrical and as slim as possible. An ideal peak shape can be described
by a Gauss function and the corresponding statistical parameters (like width-at-half
maximum or standard deviation) can be used for a qualitative evaluation (see
Fig. 3.17). Slim peaks result in a high chromatographic resolution. Beside the
width of a peak the separation ‘distance’ of individual peaks is the second important
criterion, often called separation capacity. Both chromatographic properties, resolution and separation capacity, can be influenced by various individual parameters of a
distinct chromatographic technique. The general influence of both factors is illustrated in Fig. 3.18. However, both parameters interfere, since a good separation
capacity often results in longer chromatographic times, which induces broader peaks
(lower resolution) due to the increase of diffusion processes with time. Hence,
optimizing the efficiency of a chromatographic separation needs a very balanced
improvement of both principal parameters.
General Note
Applying successfully chromatography needs a principal understanding of the
main factors influencing the chromatographic efficiency. The resolution and
the separation capacity.
Chromatography is used in analytical approaches in two different modes of
application. High-performance chromatography such as gas chromatography
(GC) and high-performance liquid chromatography (HPLC) are used directly linked
to powerful detector systems such as mass spectrometry (MS). These applications
are also known as hyphenated techniques and are discussed in detail in Chap. 4.
Low-performance chromatography is often used for a coarse separation of raw
t 0
t 1
t 2
t 3
sample
eluent
C
R f1 R f2
x
1 st order chromatogram
Fig. 3.15 Scheme of a first order chromatogram
32
3 Sample Treatment
parameters. A first criterion for a good chromatography is the shape of the peak. It
should be symmetrical and as slim as possible. An ideal peak shape can be described
by a Gauss function and the corresponding statistical parameters (like width-at-half
maximum or standard deviation) can be used for a qualitative evaluation (see
Fig. 3.17). Slim peaks result in a high chromatographic resolution. Beside the
width of a peak the separation ‘distance’ of individual peaks is the second important
criterion, often called separation capacity. Both chromatographic properties, resolution and separation capacity, can be influenced by various individual parameters of a
distinct chromatographic technique. The general influence of both factors is illustrated in Fig. 3.18. However, both parameters interfere, since a good separation
capacity often results in longer chromatographic times, which induces broader peaks
(lower resolution) due to the increase of diffusion processes with time. Hence,
optimizing the efficiency of a chromatographic separation needs a very balanced
improvement of both principal parameters.
General Note
Applying successfully chromatography needs a principal understanding of the
main factors influencing the chromatographic efficiency. The resolution and
the separation capacity.
Chromatography is used in analytical approaches in two different modes of
application. High-performance chromatography such as gas chromatography
(GC) and high-performance liquid chromatography (HPLC) are used directly linked
to powerful detector systems such as mass spectrometry (MS). These applications
are also known as hyphenated techniques and are discussed in detail in Chap. 4.
Low-performance chromatography is often used for a coarse separation of raw
t 0
t 1
t 2
t 3
sample
eluent
C
R f1 R f2
x
1 st order chromatogram
Fig. 3.15 Scheme of a first order chromatogram
32
3 Sample Treatment