AdvancedGasChromatography–Progress inAgricultural, Biomedical and Industrial Applications
30
instance, many stationary phases undergo degradation or decomposition at operating
temperatures above 250
0
C, resulting in a lower operating life. On the other hand, certain
components of unknown mixtures may reversibly or irreversibly poison the stationary
phase components, deactivating it over time. In such cases, entry within the stationary
phase canbe accomplishedusingguarded columns that retain thepoisonous components. It
isvital that these components areknown so as toprevent poisoningprecious columns.
Before usage, the stationary phases placed into the GC columns must be conditioned and
activated through streaming themobilephase – thepermanent gas.
Overall, stationary phases constitute a solvent with different selectivity for each component
of themixture in the analyzed sample.
2. Adsorption
Solid adsorbents as powdery material perform two functions in chromatography: the
adsorbent itself (GS), in which case the separation takes place by adsorption, and support
for stationaryphase (non-volatile liquid), liquid stationaryphase (GLS) coatedon agranular
material, inwhich case the separation takes place by absorption. Commonly, the size of the
solid material used in chromatography is in the range of mesh (mesh - the number of
openings per linear inch of a screen). Conversion between the Anglo Saxon and European
expression (inmm) ispresented inTable 1.
U.s.
Mesh
Inches
Microns
Millimetres
U.s.
Mesh
Inches
Microns
Millimetres
3
0.2650
6730
6.730
40
0.0165
400
0.400
4
0.1870
4760
4.760
45
0.0138
354
0.354
5
0.1570
4000
4.000
50
0.0117
297
0.297
6
0.1320
3360
3.360
60
0.0098
250
0.250
7
0.1110
2830
2.830
70
0.0083
210
0.210
8
0.0937
2380
2.380
80
0.0070
177
0.177
10
0.0787
2000
2.000
100
0.0059
149
0.149
12
0.0661
1680
1.680
120
0.0049
125
0.125
14
0.0555
1410
1.410
140
0.0041
105
0.105
16
0.0469
1190
1.190
170
0.0035
88
0.088
18
0.0394
1000
1.000
200
0.0029
74
0.074
20
0.0331
841
0.841
230
0.0024
63
0.063
25
0.0280
707
0.707
270
0.0021
53
0.053
30
0.0232
595
0.595
325
0.0017
44
0.044
35
0.0197
500
0.500
400
0.0015
37
0.037
Table 1.Mesh tomillimetres conversion chart
Hereinafterwe present the advantages of adsorption chromatography, which takes place at
gas solid interaction, compared toGLS.
