ADV01-05_1-298

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www.restekcorp.com

Faster GC Analysis of Volatile Organics

Using an Rtx

-624 Capillary GC Column and a New MegaMix

™

Reference Mix

By Christopher English, Environmental Innovations Chemist, and Katia May, Ph.D., Senior R&D Chemist

✔

New MegaMix

™

completes a line of reference materials for volatile organics in wastewater.

✔

High concentration mixes—more analyses per ampul.

✔

Rtx

-624 column: fast analysis, excellent resolution of early-eluting gases.

In the US Environmental Protection Agency method

for determining 31 volatile organic pollutants in

wastewater, EPA Method 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 packing material in a

sorbent trap. The concentrated sample is transferred

to the chromatographic column by heating the trap

under carrier gas flow.

Our new

Volatiles MegaMix

™

EPA Method 624

includes the 26 target compounds in Method 624 that

are not gases at ambient temperature and pressure.

The 5 target gases in Method 624—bromomethane,

chloromethane, chloroethane, trichlorofluo-

romethane, and vinyl chloride—are components in

our 624 Calibration Mix #1 (cat.# 30020). We pre-

pare the new MegaMix

™

, and the gas mix, 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 in Method 624,

2-chloroethyl vinyl ether, is stable in solution by

itself, but hydrolyzes to the enol form in weakly

acidic media, then converts to the aldehyde and

ketone forms. Because the halocarbon target ana-

lytes in Method 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 decided we could include

it in our MegaMix

™

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 should monitor the sta-

bility of this compound in working solutions, regard-

less of what reference material is the source of the

compound. To meet 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, to monitor laboratory performance.

Figure 1

—Rapid analysis of Method 624 analytes, with excellent chromatography for early-eluting gases, using a short, narrow bore Rtx®-624 column.

Rtx

-624, 40m, 0.18mm ID, 1.0µm (cat.# 40925)

Sample:

624 Internal Standard Mix (cat.# 30023)

624 Surrogate Standard Mix (cat.# 30243)

Volatiles MegaMix

™

EPA Method 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 RO water

Purge:

11 min. @ 40 mL/min. @ ambient temperature

Dry purge:

1 min. @ 40mL/min. (MCS bypassed using Silcosteel

tubing)

Desorb preheat:

245°C

Desorb:

250°C for 2 min., flow 10mL/min.

Bake:

260°C for 8 min.

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:

1.1 mL/min.

Dead time:

2.06 minutes @ 50°C

Oven temp.:

50°C (hold 4 min.) to 100°C @ 12°C/min. (no hold)

to 330°C @ 27°C/min. (hold 2 min.).

Det.:

Agilent 5971A GC/MS

Transfer line temp.:

280°C

Scan range:

35-260 amu

Tune

PFTBA/BFB

Ionization:

1. chloromethane

2. vinyl chloride

3. bromomethane

4. chloroethane

5. trichlorofluoromethane

6. 1,1-dichloroethene

7. methylene chloride

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