Rtx®-Dioxin2Column
• Isomer specificity for 2,3,7,8-TCDD and2,3,7,8-TCDF achievedwithoneGC column.
• Thermally stable to340°C for longer lifetime.
• Unique selectivity for toxic dioxin and furan congeners allowuse as aprimaryor confirmation
GC column.
Accurate GC analysis of polychlorinated dibenzodioxin (PCDD) and polychlorinated dibenzofuran
(PCDF) congeners is a challenge, evenwhenusingahigh resolutionmass spectrometer. Separationof the
toxic congeners (substitutions at the2, 3, 7, and8positions) from thenontoxic congenersprovesdifficult
on almost all stationary phases.Most laboratories perform an initial analysis using a 5% diphenyl/95%
dimethyl polysiloxane column (e.g., anRxi™-5ms column) toobtain reasonable estimates of concentra-
tions for the 2,3,7,8-substituted congeners. For someof the target congeners, this quantification is biased
toward high values, due to coelution with non-toxic congeners. For example, as many as five nontoxic
TCDFs can coelute with 2,3,7,8-tetrachlorodibenzofuran in an analysis on a 5% diphenyl or equivalent
column. The coelution issue has resulted in the need for confirmation columns, most commonly high
cyanopropyl stationaryphases(e.g.,Rtx®-225andRtx®-2330columns), inorder tomoreaccuratelyquan-
tify the toxiccongeners.Unfortunately, cyanopropyl columns exhibitpoor thermal stability, and therefore
offer poor lifetime. To address these issues Restek designed the Rtx®-Dioxin2 column, a column with
unique selectivity for both2,3,7,8 substituteddioxins and furans that alsohas excellent thermal stability.
Resolutionof2,3,7,8-TCDDand2,3,7,8-TCDF
The Rtx®-Dioxin2 column is specific for both 2,3,7,8-TCDD and 2,3,7,8-TCDF, something that usually
requires theuseof at least twoGC columns.The column is stable to340°C, and is available in thedimen-
sions commonly used for this analysis. Figure 1 shows a chromatogramof tetrachlorodibenzodioxins in
lake sediment extract (certified referencematerialWMS-01) on a 60m, 0.25mm, 0.25µmRtx®-Dioxin2
column. 2,3,7,8-TCDD is well-resolved from the other congeners in this group and can be quantified
accurately inWMS-01 and other samples (Table 1). The data in Figure 2 illustrate resolution of the
2,3,7,8-TCDF congener from thenontoxic congeners in the same sediment extract analyzedon anRtx®-
Dioxin2 column. Values for 2,3,7,8-TCDF in a variety of sample types obtainedwith an Rtx®-Dioxin2
column compare favorably with values obtained on a cyanopropyl-type column (the column typically
used for TCDF specificity) andwith the certified values (Table 2).However, the quantified values from
the 5%diphenyl column are biasedhighdue tootherTCDF interferences.
Table I
Comparative results (pg/g) for 2378-TCDD incertified referencematerials.
Sample
5% diphenyl
Rtx
®
-Dioxin2
Certified Value
Sediment (WMS-01)
21
14
17.7± 5.6
Sediment
8.5
9
6
Flyash
5.6
4.4
5
Flyash-2
< 3
4.4
4
Table2
Comparative results (pg/g) for 2378-TCDF incertified referencematerials.
Note thequantitativebias for the5%diphenyl resultsdue tootherTCDF interferences.
Sample
5% diphenyl
225
Rtx
®
-Dioxin2
Certified Value
Sediment (WMS-01)
78
46
47
52.5± 16
Sediment
37
19
19
23
Flyash
240
38
32
31
Flyash-2
250
40
32
28
WMS-01was obtained fromWellington Laboratories, Inc., Guelph, Ontario, Canada.
WMS-01was obtained fromWellington Laboratories, Inc., Guelph, Ontario, Canada.
