ADV01-05_1-298

• 13 •

www.restekcorp.com

by Gary Stidsen, Environmental Innovations Team Manager

Analysis of PAHs

Using Rtx

-5Sil MS and Rtx

-CLPesticides2

Capillary Columns

Analysis of polycyclic aromatic hydrocarbons

(PAHs) is a very common method in environmental

laboratories. US Environmental Protection Agency

(EPA) Method 8100 requires gas

chromatography/flame ionization detection

(GC/FID) to quantitate PAHs found in extracts from

soil, water, or biological samples. Confirmational

analysis increases the confidence of proper identifi-

cation and quantitation of the PAHs, and good reso-

lution is necessary for proper quantitation. The

most difficult compound pairs to resolve are

benzo(b)/benzo(k)fluoranthene and indeno(1,2,3-

cd)pyrene/dibenzo(a,h)anthracene. Short analysis

time is another key consideration for most laborato-

ries. By decreasing analysis time, sample throughput

increases and the lab benefits from a cost savings.

For this analysis, the primary analytical stationary

phase is a 5%diphenyl/95%dimethyl-polysiloxane

polymer. The Restek Rtx

-5Sil MS column is an

Figure 1

The Rtx

-5Sil MS column exhibits excellent resolution of PAHs including

benzo(b)/benzo(k)fluoranthene in less than 17 minutes.

✔

benzo(b)/benzo(k)flouranthene

resolution

✔

Optimized conditions yield

18-minute analysis time

equivalent phase and is recommended for this

analysis (Figure 1). The confirmational column

recommended by Restek for this analysis is the

Rtx

-CLPesticides2 column (Figure 2). Quantitative

reliability for this analysis is maintained because the

stationary phases differ in selectivity, resulting in

retention time shifts of both PAHs and interference

compounds.

Resolution between benzo(b)fluoranthene and

benzo(k)fluoranthene, and indeno(1,2,3,-

cd)pyrene and dibenzo(a,h)anthracene is essential

for quantitation when using an FID. To achieve

excellent resolution of these peak pairs, the carrier

gas, column flow rate, and temperature program

must all be optimized. These three parameters

should be optimized to increase throughput, too. To

achieve even better quantitative reliability, it is rec-

ommended to clean sample extracts following EPA

Method 3630 (silica gel) prior to analysis.

Optimizing the temperature program contributes to

better resolution of closely eluting peak pairs and

shortens analysis times. The temperature program

and other conditions in Figures 1 and 2 achieve

baseline resolution of indeno(1,2,3-cd)pyrene and

dibenzo(a,h)anthracene, and excellent resolution

of benzo(b)fluoranthene and benzo(k)fluoran-

thene, while still keeping the analysis time under

18 minutes. Because the temperature program for

both columns is the same, the analysis can be run

simultaneously on the primary and confirmation

columns.

PAH analysis by US EPA Method 8100 can be

improved by choosing the appropriate analytical

columns and by optimizing the temperature pro-

gram, carrier gas, and column flow rates. When

operating under the conditions listed for Figures 1

and 2, the Rtx

-5Sil MS and the Rtx

-CLPesticides2

columns yield excellent resolution and short analy-

sis times for PAHs.

1. naphthalene

2. acenaphthylene

3. acenaphthene

4. fluorene

5. phenanthrene

6. anthracene

7. fluoranthene

8. pyrene

30m, 0.25mmID, 0.25µm Rtx

-5Sil MS (cat.# 12723);

Sample:

Method 610—Polynuclear Aromatic Hydrocarbons

Mix (cat.# 31011);

Concentration:

50ppm;

Solvent:

methylene chloride;

Sample size:

1.0µL;

GC:

Thermo Trace 2000

Series;

Injector:

splitless @ 250°C;

Splitless hold time:

2.0 min.;

Split vent flow:

40cc/min.;

Carrier gas:

hydrogen

(constant flow mode);

Column flow rate:

4.0cc/min. @ 40°C;

Linear velocity:

43cm/sec.;

Detector:

FID @ 340°C;

Make-up gas flow:

40cc/min.;

Oven program:

40°C (hold 2.0 min.) to 268° C @ 25°C/min. (hold 1.0 min.)

to 330°C @ 5°C/min. (hold 10 min.)

2 3

1415 16

Figure 2

The Rtx

-CLPesticides column is an excellent confirmational column for PAH analysis.

2 3

5 6

109

14 15 16

9. benzo(a)anthracene

10. chrysene

11. benzo(b)fluoranthene

12. benzo(k)fluoranthene

13. benzo(a)pyrene

14. indeno(1,2,3-cd)pyrene

15. dibenzo(a,h)anthracene

16. benzo(g,h,i)perylene

1. naphthalene

2. acenaphthylene

3. acenaphthene

4. fluorene

5. phenanthrene

6. anthracene

7. fluoranthene

8. pyrene

9. benzo(a)anthracene

10. chrysene

11. benzo(b)fluoranthene

12. benzo(k)fluoranthene

13. benzo(a)pyrene

14. indeno(1,2,3-cd)pyrene

15. dibenzo(a,h)anthracene

16. benzo(g,h,i)perylene

30m, 0.25mm ID, 0.25µm Rtx

-CLPesticides2 (cat.# 11323);

Sample:

Method 610—Polynuclear Aromatic

Hydrocarbons Mix (cat.# 31011);

Concentration:

50ppm;

Solvent:

methylene chloride;

Sample size:

1.0µL;

GC:

Trace 2000 Series;

Injector:

splitless @ 250°C;

Splitless hold time:

2.0 min.;

Split vent flow:

40cc/min.;

Carrier gas:

hydrogen (constant flow mode);

Column flow rate:

4.0cc/min. @ 40°C;

Linear velocity:

43cm/sec.;

Detector:

FID @ 340°C;

Make-up gas flow:

40cc/min.;

Oven program:

40°C (hold 2.0 min.) to 268°C @ 25°C/min.

(hold 1.0 min.) to 330°C @ 5°C/min. (hold10 min.)

For the complete Rtx

-5Sil MS and

Rtx

-CLPesticides2 columns offering, refer to

Restek’s

Annual Chromatography Products Catalog

(lit. cat.# 59960).

✔

Rtx

-5Sil MS Columns

Temp limits: -60 to 330/350°C

ID (mm)

df (µm)

30-Meter

0.25

12723

0.32

0.25

12724

✔

Rtx

-CLPesticides2 Columns

Temp limits: -60 to 310/330°C

ID (mm)

df (µm)

30-Meter

0.25

0.20

11323

0.32

0.25

11324

for

more

info

Request Applications Note # 59196.

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