restekadv07 - page 185

with data pack
with data pack
with data pack
Inlet activity is the primary drawback to using hot
flash injectionwhen analyzing chlorinated pesticides
by GC. Residues of heavier and non-volatilemateri-
als often build up throughout the injection port,
leaving a reactive surface that can cause compounds
such as endrin andDDT to break down. An inlet
liner that provides a press-fit connection between
the column and the liner eliminates reactive surface
problems associatedwith the bottom portion of the
injection port. A physical connection between the
column and the liner also improves sensitivity, by
minimizing injection port discrimination.
This article summarizes the advantages of using a
RestekDrilledUniliner® inlet liner (Figure 1) and an
Rtx®-CLPesticides/Rtx®-CLPesticides2 column pair for
chlorinated pesticides analysis. Included are com-
parisons of data obtained using aDrilledUniliner®
inlet liner to data obtained using a conventional split-
less inlet liner, and a splitless inlet liner packedwith
fused silicawool.
• 12 • www.restekcorp.com 800-356-1688
by Lydia Nolan, Environmental Innovations Chemist
ImprovedResponses for
ChlorinatedPesticides
Using a DrilledUniliner® GC Inlet Liner and
Rtx®-CLPesticides Columns
✔ Less breakdown of active compounds, formore accurate results.
✔ Greater sensitivity, for lower detection limits.
✔ Minimal injection port discrimination.
✔ Liner accommodates direct or splitless injections.
Procedures detailed in US EPAMethods 8081 and
8000 require each laboratory to document that the
quantification results they generate are reliable,
precise, and accurate. Beginning with a five-point
calibration curve, a calibration factor is calculated
for each analyte. The relative standard deviation
(RSD) should be nomore than 20% for each ana-
lyte. Using a Drilled Uniliner® inlet liner, mean RSD
values for 20 chlorinated pesticides for the Rtx®-
CLPesticides column and for the Rtx®-CLPesticides2
columnwere 4.1% and 4.5% respectively. High val-
ues were 12.5% and 14.2%.
A calibration standardmust be analyzed and quanti-
fied regularly. The concentration of each analyte in
this standard should be within±15% of the “true”
value. The accuracy of data obtained by using a
Drilled Uniliner® inlet liner was testedwith pesti-
cide standardmix at the 20/40/200ng/mL concen-
tration level (Figure 2). For either column, the
mean percent difference from the “true” value for
each analyte was only ±2.2%, well within the
acceptable limits.
Finally, because some analytes readily break down
as the injection port inlet becomesmore contami-
nated (e.g., endrin andDDT in this analysis), a per-
formance evaluationmixmust be analyzed and
breakdown for each analyte calculated. Breakdown
should not exceed 15%. The Drilled Uniliner® inlet
liner reduces endrin andDDT breakdown, relative
to the splitless liners (Table 1), because it shields
the analytes from contact with active surfaces out-
side the inlet liner. Wool packing in the splitless
linermakes this problemworse, because it greatly
increases the surface area and potential active sites.
In addition to reducing variability and increasing
accuracy of calibration data, the Drilled Uniliner®
inlet liner increases overall response for individual
analytes, because injection port discrimination is
greatly reduced. This enhancesminimum detection
levels, compared to standard splitless inlet liners.
This ismost apparent from the area counts for the
last eluting analyte, decachlorobiphenyl, which
were greater by 18-39%, relative to area counts for
injectionsmade on the splitless liners (Table 1).
By eliminating the bottom of the injector from the
sample pathway, a Drilled Uniliner® inlet liner
makes the pathwaymore inert. This reduces break-
down of labile analytes, such as endrin andDDT
and increases accuracy and precision. For analysts
using hot flash injection techniques in analyses of
chlorinated pesticides, or other labile analytes,
these results clearly indicate that the Drilled
Uniliner® inlet liner is the liner of choice.
%Breakdown
Drilled 4mm splitless 4mm splitless
Analyte Column Uniliner® withwool
Endrin Rtx®-CLPesticides 4.4 4.7 9.8
Rtx®-CLPesticides2 4.9 6.9 8.3
DDT Rtx®-CLPesticides 0.2 0.3 2.6
Rtx®-CLPesticides2 0.3 0.9 3.1
Response*
Drilled 4mm splitless 4mm splitless
Analyte Column Uniliner® withwool
Tetrachloro- m- Rtx®-CLPesticides 147 111 106
xylene (TCMX) Rtx®-CLPesticides2 191 167 162
Decachloro- Rtx®-CLPesticides 150 119 108
biphenyl (DCB) Rtx®-CLPesticides2 209 177 166
*Mean response (n=2); value in table x 103 = response units.
Figure 1
The drilled hole in a Uniliner® injection port
linermakes direct injection possiblewith
EPC systems by equalizing pressure in the
injection port.
Table I
Lowest breakdown of endrin andDDT, and highest responses for analytes, using a Drilled
Uniliner® inlet liner.
aldrin 8µg/mL
α-BHC 8
β-BHC 8
δ-BHC 8
γ-BHC (lindane) 8
α-chlordane 8
γ-chlordane 8
4,4'-DDD 16
4,4'-DDE 16
4,4'-DDT 16
dieldrin 16
endosulfan I 8
endosulfan II 16
endosulfan sulfate 16
endrin 16
endrin aldehyde 16
endrin ketone 16
heptachlor 8
heptachlor epoxide (B) 8
methoxychlor 80
In hexane:toluene (1:1), 1mL/ampul
OrganochlorinePesticideMix AB #2
(20 components)
Each 5-pk. 10-pk.
32292 32292-510 —
32292-500 32292-520 32392
decachlorobiphenyl
2,4,5,6-tetrachloro- m-xylene
200µg/mL each in acetone, 1mL/ampul
Pesticide SurrogateMix
04.1, 3/90, 4/89, and 2/88 SOW
Each 5-pk. 10-pk.
32000 $18.60 32000-510 —
32000-500 $28.90 32000-520 32100
α-BHC 1µg/mL
β-BHC 1
γ-BHC (lindane) 1
4,4'-DDT 10
decachlorobiphenyl 2
endrin 5
methoxychlor 25
2,4,5,6-tetrachloro- m-xylene 2
In hexane, 1mL/ampul
PesticidePerformance EvaluationMix
w/Surrogates (8 components)
04.1 and 3/90 SOW
Each 5-pk. 10-pk.
32074 $28.90 32074-510 —
32074-500 $39.20 32074-520 32174