Tech-Tips
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RestekCorporation • (800)356-1688 • (814)353-1300 •
#59108
tech-tips
ImprovedGCAnalysisof BasicOrganicCompoundsUsingBase-Deactivated
Columns and Inlet Liners
The gas chromatographic (GC) analysis of basic organic com-
pounds (e.g., amines, basic drugs, and azo dyes) is a challenge to
the analyst, especiallywhen the compounds are at low concentra-
tions. The challenge ismainly caused by acidic silanol groups on
the pathway surfaces ofGC system (i.e., inlet liner, wool, guard
and analytical columns) that remain after standard chemical
deactivation.Vaporized basic compounds are adsorbed onto the
active sites, causing peak tailing and reduced response.
Because of the interaction between basic compounds in the
samplewith acidic active sites in the sample pathway, a “prim-
ing” effectmay be noticed.With priming, the first injection of a
basic sample results in compounds adsorbing onto the active sites
and covering them. Repeated injections causemore andmore
sites to be covered until an equilibrium is reached. Response
subsequently improves, but reproducibility is poor. The priming
effect is temporary because the systemwill revert back to an
adsorptive state after column conditioning or periods of inactivity.
Restek has an entire line of base-deactivated products to aid in the
analysis of basic compounds—inlet liners, fused silicawool,
guard columns, and theRtx
®
-5Amine analytical column.
(Restek’s analytical column deactivated specifically for the
analysis of organic basic compounds). Base-deactivation is a
unique deactivation process that bonds basic functional groups to
Figure2
TheRtx
®
-5Amine columnachieves better response for active basic compounds compared to the standard5%phenyl column.
1. pyridine
2. 1,2-butanediol
3. C10
4. diethylene triamine (3AM)
5. diethanolamine (DEA)
6. 2-nonanol
7. 2,6-diethylaniline
8. dodecane
Rtx
®
-5AmineColumn
Rtx
®
-5Column
30m, 0.32mm ID, 1.0µmRtx
®
-5Amine (cat.# 12354)
and a base-deactivated4mmgooseneck sleevewith
base-deactivatedwool (cat.# 20798-211.1).
30m, 0.32mm ID, 1.0µmRtx
®
-5 (cat.# 10254)
and a 4mm gooseneck sleevewithwool (cat.# 20798-200.1).
Figure1
Base-deactivated liner/wool systemprovidesbetter
diethanolamine response.
SplitlessGooseneck
Liner w/Wool
Direct Open-Top
Uniliner
®
w/Wool
Base-
Deactivation
Standard
Deactivation
80
60
40
20
Response
RSD
RSD
Response
%
the analytical surface. These functional groups on the surface
greatly reduce adsorption and priming effects, thereby improving
peak shape, response, and reproducibility. Figure 1 compares the
effect of a base-deactivated liner/wool systemwith a standard-
deactivated liner/wool system on diethanolamine response. In
RSD=standard
deviation
Oven temp.:
90°C isothermal
Inj.&det. temp.:
300°C
Detector:
FID
Carrier gas:
helium@36cm/sec
Split vent:
40mL/min.
1
2
3
4
5
7
6
8
min. 0
30
1
2
3
7
6
8
min. 0
30
➞➞➞➞➞
➞➞➞
➞➞➞
➞➞➞
No response for
3AM/DEA
Good response for
3AM/DEA
