RestekCorporation • (800)356-1688 •
Figure2
Siltek
™
deactivation remains effective at an injection port temperature of 330°C for ten days.
Thermal Stability
To test the durabilityof theSiltek
®
liner deactivation, two
sources of stresswere investigated—high inlet temperatureover
aperiodof 10days and repeated exposure to aqueous injections
of low, thenhighpH.High inlet temperatures canpromote
degradationof the deactivation layer by causing it tobake or
bleedoff of the liner. In the first study, a baseline splitlessXTI
injectionwas performed, and response factors (relative toC14)
were calculated. The injectionportwas then set at 330°C
overnight and anotherXTI injectionwasmade. This processwas
continued for 10days.After 10days at 330°C, theSiltek
®
deactivation retained its integrity, achievingessentiallyunchanged
response factors, even for thecritical probes (Figure2).
Resistance toChemicalAttack
For the next durability study, aSiltek
®
-deactivated linerwas
repeatedly exposed to aqueousHCl injections, pH1.4.The
ability towithstand lowpH aqueous samples is importantwith
environmental applications that require acidificationof the
matrix.Very lowor veryhighpH samples can cause pinpoint
holes in the deactivation layer thatwill eventuallyundercut the
layer and strip it away. For this study, a baselineXTI injection
wasmade via direct injection and relative response factorswere
calculated. In the direct injectionmode, a leak-free connection is
formed in the liner,minimizing sample exposurewithin the
injectionport.Tenmicroliters of the pH1.4 samplewere
injected, followedby a direct injectionof theXTI testmixture.
This cycle continueduntil a total of 180µLwere injected (Figure
3).Keyprobes, such as 2,4-dinitrophenol (DNP), pentachlo-
rophenol (PCP),
N
-nitroso-di-
n
-propylamine (
n
-propylamine),
and1,2-hexanediol (diol) retained their responses up to at least
120µL injected.
The experimentwas repeatedwith an identical set-upusing
aqueousNH
4
OH injections, pH10.1 (Figure 4).Under these
demanding conditions, the response for theXTI compoundswas
consistent for 70 injections.As expected, the response of the
acidic compounds began todecreasewith repeated injections but
many compounds continued tohave excellent response formore
than120µL injections.
Siltek
®
deactivationoffers both inertness and resistance to
temperature andpH extremeswithin aGC system. It is available
as a deactivation for fused silica guard columns and inlet liners.
Formore informationonSiltek
™
—
thenext generationof deactivation,
please request our Siltek
™
Benefits
brochure (cat.# 59803).
30m, 0.25mm ID, 0.25µmXTI
®
-5 (cat.# 12223) with a Siltek
™
-deactivated splitless sleeve (cat.# 20798-214.1).
Oven temp.:
40°C (hold 2min.) to
190°C@ 6°C/min., to 330°C@ 30°C/min. (hold 10min.);
Inj. temp.:
330°C;
Det.:
330°C;
Carrier gas:
He.
1,2-hexanediol
N
-nitroso-di-
n
-propylamine
benzoic acid
2,4-dinitrophenol
4-nitrophenol
4-nitroaniline
pentachlorophenol
Day 1
Day 5
Day 7
Day 9
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
ResponseRelative toC14
#Days InjectionPort at 330°C
