ADV01-05_1-298

• 6 •

www.restekcorp.com

800-356-1688

Various methods have provided guidelines for

GC/electron capture detection (GC/ECD) analysis of

organochlorine pesticides and PCBs in aqueous and

soil matrices. Pesticides and PCB congeners now are

analyzed by separate methods, to ensure more accu-

rate PCB data and eliminate complications that arise

in combined analysis. Analyses of individual PCB

congeners greatly simplify quantitative studies, and

improve data, relative to the difficult quantitative

studies of PCBs as mixtures (e.g., Aroclor

mix-

tures)—especially with mixtures weathered by long

exposure in the environment.

GC analysis of organochlorine pesticides and PCBs

can be very challenging because of lengthy calibra-

tions, linearity problems, and potential breakdown

of some of the pesticides. In addition to adequate

resolution of the target analytes, the column for this

analysis must exhibit low bleed. A wide-bore

(0.53mm ID) column is listed in US EPA Methods

8081A and 8082A for organochlorine pesticides,

but a narrow-bore column may be used in single-

column analyses. Our new 0.32mm ID, 0.5µm

phase Rtx

-XLB column is ideal for analyses of

active compounds, due to improvements in polymer

synthesis and tubing deactivation. Figure 1, an

analyses of 20 organochlorine pesticides

(Organochlorine Pesticide Mix AB #2, cat.#

32292), demonstrates the superior efficiency and

low bleed characteristic of the new column, even at

330ºC. The column, in combination with a high ini-

tial temperature, 120ºC, reduced analysis time to

11.5 minutes, with excellent separation. Very low

bleed and high thermal stability ensure reliable

detection at the 80/160/800 ppb level. The very low

bleed also minimizes detector contamination, pro-

longing intervals between cleanings and thus

increasing throughput over time. Note that to mini-

mize breakdown of labile pesticides we minimized

sample contact with metal surfaces by using a

Drilled Uniliner

inlet liner to convey the sample

directly onto the column.

Restek chemists carefully reviewed EPA Methods

8080 and 8081A, then developed three calibration

mixes that include 20 most often monitored

organochlorine pesticides. The mix used to obtain

Figure 1 has varied concentrations of the target ana-

lytes, from 8 to 80µg/mL, because these pesticides

exhibit significantly differing responses.* The other

two mixes include the 20 analytes at a single concen-

tration, 200µg/mL or 2000µg/mL. The 2000µg/mL

concentration often is more practical than lower

concentrations, especially if several mixes must be

combined. We also offer all surrogates and internal

standards currently required for these analyses.

PCBs are persistent in the environment, and accu-

rately determining their presence and concentrations

is very important. A common question is whether

such analyses should be focused on mixtures of

PCBs (e.g., Aroclor

mixes) or on individual con-

geners. Congener-specific analyses have important

advantages over analyses of mixtures: generally, con-

gener analyses offer lower detection limits and

greater information content. In addition, composi-

tions of weathered, degraded, and metabolized PCB

mixtures can be measured and interpreted more

easily. Also, it is easier to detect interferences caused

by other chemicals, and quantification of individual

congeners is more accurate. However, coelution of

analytes is a problem in a PCB congener analysis, so

a strong quality assurance program and reliable ref-

erence materials are needed by the analyst. To facili-

tate congener-specific analyses, we now make a ref-

erence mix of 19 PCB congeners at 100µg/mL each

in isooctane, suitable for EPA Method 8082A.

Depending on regulatory and project requirements,

GC/ECD Analysis of Organochlorine Pesticides or

Polychlorinated Biphenyls

Using a Low-Bleed Rtx

-XLB Column and Restek Reference Materials

by Greg France, Innovations Chemist, Gary Stidsen, Innovations Team Manager,

and Katia May, Ph.D., Senior R&D Chemist

✔

Rtx

-XLB column shows extremely low bleed and excellent inertness, improving sensitivity

for active compounds.

✔

20 common organochlorine pesticides in 3 convenient reference concentrations.

✔

19 US EPA Method 8082A PCB congeners in one solution.

Figure 1

Organochlorine pesticides separated in less than 12 minutes, using an Rtx®-XLB column.

1. 2,4,5,6-tetrachloro-

-xylene (ss)

-BHC

6. heptachlor

7. aldrin

8. heptachlor epoxide

-chlordane

10.

-chlordane

11. endosulfan I

12. 4,4'-DDE

13. dieldrin

14. endrin

15. 4,4'-DDD

16. endosulfan II

17. endrin aldehyde

18. 4,4'-DDT

19. endosulfan sulfate

20. methoxychlor

21. endrin ketone

22. decachlorobiphenyl (ss)

Rtx

-XLB 30m, 0.32 ID, 0.5µm (cat.# 12839)

Sample:

Organochlorine Pesticide Mix AB (cat.# 32292) 80/160/800ppb in hexane

2,4,5,6-tetrachloro-

-xylene (cat.# 32027) surrogate, 80ppb

decachlorobiphenyl (cat.# 32029) surrogate, 160ppb

Inj.:

1.0µL splitless (0.75 min. hold), 4mm Drilled Uniliner

inlet liner (cat.# 21055)

Inj. temp.:

220°C

Carrier gas:

hydrogen, constant pressure

Linear velocity: 60cm/sec. @ 120°C

Oven temp.:

120°C (hold 0.5 min.) to 260°C @ 29°C/min. (hold 2.5 min.), to 330°C @ 28°C/min. (hold 3 min.)

Det.:

ECD @ 320°C

GC_EV00720

*For mix composition, see page 8 of this

Advantage.