20m, 0.18mm ID, 1.0µmRtx
®
-502.2 column (cat.# 40914), 4ppb ofVOA standards.
Oven temp.:
35°C (hold 5min.) to 180°C@ 6°C/min.
to 210°C@ 20°C/min. (hold 5min.)
Inj. / det. temp.:
100°C / 280°C
Linear velocity:
20cm/sec. set@ 35°C
Purge& trap:
Tekmar 3000
Purge:
11min.
Trappressure control:
6psi
Desorbpreheat:
250°C
Desorb time:
2min.
Detector:
MS
Split ratio:
40:1
Scan range:
35-260AMU
Trap:
Vocarb
™
3000
Desorb temp.:
260°C
Desorb flow rate:
20mL/min.
16
Figure 11.
Nomeasurable response for bromoform (9), combinedwith a greatly diminished response
for 1,1,2,2-tetrachloroethane (10), strongly indicates a contaminated transfer line.
Instructions for CleaningPurge andTrapConcentrators
We developed these instructions usingTekmar LSC 2000 and 3000 concentrators.Always
remember to use safety glasseswhenworking in the laboratory.
1. Keep the instrument power on and turn the line heaters off. Set all temperatures to the off
position.WAITUNTILHEATEDZONESHAVECOOLED.
2.Make sure the unit is in standbymode.
3. Disconnect the purge and trap vessel.
4. Flushmethanol into the areawhere the top of the trap attaches, using a 5mL syringe
without a needle (i.e., a Luer-lock syringe - see photo). This is the areawhere the purge
vessel attaches to the purge and trap.You should seemethanol coming out of themount.
5. Clean themount, using a tissue. Themount is either nickel- or gold-plated, so be careful
not to scratch the surface. If you cannot clean themount, it may need to be replaced.
6. Clean the purge vessel withmethanol, thenwith ultra-purewater. Do not use soap.You
may use a brush.
7. Increase purge and trap temperatures to normal operating conditions and hold for two
hours, with no trap or purge vessel installed.
8. Install an empty trap. Do not use an old trapwith the packing removed; particles of trap-
pingmaterial may end up in the concentrator. If an empty trap is not available, refer to the
next paragraph.With the empty trap in place, attach all lines, including the line to the
purge vessel. Desorb for at least one hour with the transfer line disconnected from the col-
umn. Thiswill help to drive anymethanol remaining from step 6 out of the system.
If you do not have an empty trap, disconnect the transfer line from the column, connect
the purge vessel and all lines, and install an old trap. Desorb for one hour.
9. Install and condition a new trap and run blanks until a clean baseline is achieved.
If you are still having activity problems after following this procedure, please contact the
RestekTechnical ServiceTeam via email at
or via phone at
800-356-1688 or 814-353-1300, ext. 4.
Flushing the trap attachment areawith
methanol. Repeat several times.
20
6
11
19
21
22
23
24
min. 20
7
c-gram #216
2,3
4,5
12,13
8
10
1
14,15
18
16
25
17
Permission to publish this chromatogram
granted byAnneWilliams, Tekmar Company.
1. chlorobenzene
2. ethylbenzene
3. 1,1,1,2-tetrachloroethane
4.
m
-xylene
5.
p
-xylene
6.
o
-xylene
7. styrene
8. isopropylbenzene
9. bromoform (not detected)
10. 1,1,2,2-tetrachloroethane
11. 1,2,3-trichloropropane
12. propylbenzene
13. bromobenzene
14. 1,3,5-trimethylbenzene
15. 2-chlorotoluene
16. 4-chlorotoluene
17.
tert
-butylbenzene
18. 1,2,4-trimethylbenzene
19.
sec
-butylbenzene
20.
p
-isopropyltoluene
21. 1,3-dichlorobenzene
22. 1,4-dichlorobenzene
23.
n
-butylbenzene
24. 1,2-dichlorobenzene
EPAUpdate
The US EPA promulgated update III of Test
Methods for Evaluating SolidWaste (SW-
846). This 1997 update deleted the previous
EPA purge and trapMethod 5030A, “Sample
Preparation of Volatile OrganicCompounds for
Purge andTrapAnalysis” and replaced it with
Method 5035, “Closed SystemPurge and Trap
and Extraction for Volatile Organics in Soil and
Waste Samples.” Method 5035 involves
extensive fieldwork and raisesMDLs for soil
samples; however, accuracy is improved.
Previously, soil sampleswere collected using
Teflon
®
-lined screw-cap containers and stored
at 4°C, with a 14-daymaximum holding time.
Once the sampleswere in the laboratory, 5g
aliquots of soil were added to 5mL of reverse
osmosis (RO) water. The volatiles in these
samples exit the soil matrix and leak from the
container. Method 5035 requires samples to
be collected and preserved in the field at the
time of sampling, usingmethanol and a stir-
bar. Volatiles dissolved in themethanol are
less likely to escape. The seal is not broken
until the time of analysis, thusminimizing
analyte loss through evaporativemechanisms.
Sodium bisulfate is used to prevent biodegra-
dationof VOCs. UnlikeHCl preservation, sodi-
um bisulfate does not break down 2-
chloroethyl-vinyl-ether. This greatly improves
the accuracy of analytical results from soil
samples because evaporative loss occurs
almost immediately in soils that are not pre-
served inmethanol. Disadvantages include the
higher detection limits and the problems asso-
ciatedwith purging higher percentages of
methanol.
