RestekCorporation • (800)356-1688 •
Figure3
Untreatedmetal liners and injection port surfaceswill cause high levels of endrin andDDTbreakdown.
To compare the effects causedbyhotmetal surfaces, a splitless
injectionwasmade into anuntreated stainless steel sleeve.
Because the splitless sleeve does not form a press-tight sealwith
the analytical column, the sample vapor is less restricted and is
free to contact themetal disk located at the bottomof theHP
injectionport, aswell as the injectionport body. Endrinbreak-
down (40%)was less than in theuntreatedglass liner, butDDT
breakdown (20%)was significant (Figure3).
As a final comparison, the standardmixturewas injectedvia
direct injection into aUniliner
®
sleeve thatwas processedwith
Siltek
™
deactivation (Figure4). Endrinbreakdownmeasured less
than1%on theUniliner
®
sleeve that hadbeendeactivatedusing
theSiltek
™
deactivationprocess.DDTbreakdown againwas
belowdetection limits and, therefore, insignificant.Acompletely
deactivated system ismost effective for analyzingUSEPA
Method8081A samples on the sameHP systemused for the
previous injections (Figure5).
Several conclusions canbedrawn from the results of this series
of injections. It appears that endrin ismoreprone tobreakdown
onglass surfaces thanmetal, andDDT ismore prone tobreak
downonmetal surfaces. In addition, direct injection reduces
contact between the sample and themetal injectionport.And,
most importantly, careful deactivationof glass sleeves is crucial
forminimizingendrinbreakdown.Restek’sSiltek
™
deactivation
yields aminimal endrinbreakdownof 1%!
Our researchdemonstrates that a direct injection into aSiltek
™
-
deactivatedUniliner
®
sleeveprovides thebest protectionagainst
problematicbreakdown that occurs in the injectionportwhen
analyzing chlorinatedpesticides. For a complete, highly inert
pathway to analyze these compounds, Restek alsooffers
analytical columns for chlorinatedpesticide analysis (Rtx
®
-
CLPesticides andRtx
®
-CLPesticides2 columns) andSiltek
™
-
deactivatedguardcolumns.
1. 2,4,5,6-tetrachloro-
m
-xylene
2. 4,4'-DDE
3. endrin
4. 4,4'-DDD
5. 4,4'-DDT
6. endrin aldehyde
7. methoxychlor
8. endrinketone
9. decachlorobiphenyl
1
2
3
4
5
7
6
8
9
30m, 0.53mm ID, 0.42µmRtx
®
-CLPesticides2 (cat.# 11340).
On-column conc.:
50ppb;
Oven temp.:
120°C (hold 1min.) to 300°C@ 9°C/min.
(hold 10min.);
Inj./det. temp.:
250°C/300°C;
Purge:
on 0.75min.;
Carrier gas:
helium, 33cm/sec.
Formore informationonSiltek
™
—
thenext generationof deactivation,
please request our Siltek
™
Benefits
brochure (cat.#59803).
