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Faster GCAnalysis of VolatileOrganics
Using an Rtx
®
-624Capillary GCColumn and a NewMegaMix
™
ReferenceMix
ByChristopher English, Environmental InnovationsChemist, andKatiaMay, Ph.D., Senior R&DChemist
✔
NewMegaMix
™
completes a line of referencematerials for volatile organics inwastewater.
✔
High concentrationmixes—more analyses per ampul.
✔
Rtx
®
-624 column: fast analysis, excellent resolution of early-eluting gases.
In the US Environmental Protection Agencymethod
for determining 31 volatile organic pollutants in
wastewater, EPAMethod 624, the target volatile
organics are analyzed using purge and trap gas
chromatography/mass spectrometry. The purge and
trap system efficiently transfers the volatile analytes
from the aqueous phase to the vapor phase, from
which they are adsorbed to the packingmaterial in a
sorbent trap. The concentrated sample is transferred
to the chromatographic column by heating the trap
under carrier gas flow.
Our new
VolatilesMegaMix
™
EPAMethod624
includes the 26 target compounds inMethod624 that
are not gases at ambient temperature andpressure.
The 5 target gases inMethod624—bromomethane,
chloromethane, chloroethane, trichlorofluo-
romethane, and vinyl chloride—are components in
our 624 CalibrationMix #1 (cat.# 30020). We pre-
pare the newMegaMix
™
, and the gasmix, at a high
concentration of 2000µg/mL each component, to
enable you to conduct several analyses from each
ampul of material.
One of the target compounds inMethod 624,
2-chloroethyl vinyl ether, is stable in solution by
itself, but hydrolyzes to the enol form inweakly
acidicmedia, then converts to the aldehyde and
ketone forms. Because the halocarbon target ana-
lytes inMethod 624 are slightly acidic compounds,
2-chloroethyl vinyl ether usually is offered separately
from the other analytes. We studied the stability of 2-
chloroethyl vinyl ether and decidedwe could include
it in ourMegaMix
™
solution of Method 624 volatiles
if we also included a small amount of preservation
agent. 2-Chloroethyl vinyl ether is stable in the
MegaMix
™
mix, but analysts shouldmonitor the sta-
bility of this compound inworking solutions, regard-
less of what referencematerial is the source of the
compound. Tomeet user preference, we also offer
2-chloroethyl vinyl ether in individual solution (cat.#
30265).
Method 624 calls for spiking all samples with surro-
gate standards, tomonitor laboratory performance.
Figure1
—RapidanalysisofMethod624analytes,withexcellent chromatography for early-elutinggases, usinga short, narrowboreRtx®-624 column.
Rtx
®
-624, 40m, 0.18mm ID, 1.0µm (cat.# 40925)
Sample:
624 Internal StandardMix (cat.# 30023)
624 Surrogate StandardMix (cat.# 30243)
VolatilesMegaMix
™
EPAMethod 624 (cat.# 30497)
Purge and trap conditions:
Concentrator:
Tekmar LSC-3100 Purge and Trap
Trap:
Vocarb 3000 (type K)
compounds at 50 ppb (IS@ 40ppb) in 5mL of ROwater
Purge:
11min. @ 40mL/min. @ ambient temperature
Dry purge:
1min.@40mL/min. (MCSbypassedusingSilcosteel
®
tubing)
Desorb preheat:
245°C
Desorb:
250°C for 2min., flow 10mL/min.
Bake:
260°C for 8min.
Interface:
Silcosteel
®
transfer line, 1: 40 split at injection port.
1mm ID liner
Chromatography:
Inj. temp.:
250°C
Carrier gas:
helium, constant flow
Flow rate:
1.1mL/min.
Dead time:
2.06minutes@ 50°C
Oven temp.:
50°C (hold 4min.) to 100°C@ 12°C/min. (no hold)
to 330°C@ 27°C/min. (hold 2min.).
Det.:
Agilent 5971AGC/MS
Transfer line temp.:
280°C
Scan range:
35-260 amu
Tune
PFTBA/BFB
Ionization:
EI
1. chloromethane
2. vinyl chloride
3. bromomethane
4. chloroethane
5. trichlorofluoromethane
6. 1,1-dichloroethene
7. methylene chloride
8.
trans
-1,2-dichloroethene
9. 1,1-dichloroethane
10. bromochloromethane
11. chloroform
12. 1,1,1-trichloroethane
13. pentafluorobenzene
14. carbon tetrachloride
15. benzene
16. 1,2-dichloroethane
17. fluorobenzene
18. trichloroethene
19. 1,2-dichloropropane
20. bromodichloromethane
21. 2-chloroethyl vinyl ether
22.
cis
-1,3-dichloropropene
23. toluene
24. 2-bromo-1-chloropropane
25. 1,1,2-trichloroethane
26. tetrachloroethene
27. dibromochloromethane
28.
trans
-1,3-dichloropropene
29. chlorobenzene
30. ethylbenzene
31. bromoform
32. 1,4-dichlorobutane
33. 4-bromofluorobenzene
34. 1,1,2,2-tetrachloroethane
35. 1,3-dichlorobenzene
36. 1,4-dichlorobenzene
37. 1,2-dichlorobenzene
GC_EV00701
CO
2
