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2005 vol. 3

Restek Innovations chemists have evaluated many combinations of stationary

phase, column dimensions, and analytical conditions for analyzing environ-

mental semivolatile compounds such as those listed in US Environmental

Protection Agency Method 8270. Using a typical benchtop quadrupole mass

spectrometer, we have achieved a 15-minute analysis, while maintaining a scan

rate of at least 5 scans per target analyte.¹ Time-of-flight mass spectrometers

(TOFMS) make analysis times under 9 minutes achievable,² because they can

scan more than 100 times faster than quadrupole instruments.

After developing this analysis on a 0.18mm ID, 0.36µm column,³ our chemists

decided to experiment with a column of standard ID and phase film dimen-

sions (0.25mm ID / 0.50µm film), in an attempt to establish a similarly rapid

analysis on a larger bore column. The column they chose was a 30m x 0.25mm

ID x 0.5µm Rtx®-5Sil MS column. The target compound list included our

8270 MegaMix™ and Appendix IX Mix #2 mixes, plus internal standards and

surrogates—a total of 117 compounds. Advantages of using a 0.25mm ID col-

umn with a 0.5µm phase film include increased sample capacity and longer

column lifetime, combined with rapid analyses.

Injection Port Optimization

The first step in the experiment was to optimize conditions in the injection

port. We found that the inlet liner and seal remain inert longer when we inject

only 0.5µL of sample into the injection port. This increases the number of

passing calibration checks per liner and seal, and so reduces instrument down-

time. The key to maintaining sensitivity when injecting smaller amounts of

sample is to attain the most efficient sample transfer possible: we determined

a 2mm ID inlet liner most efficiently transfers 0.5µL samples.

Splitless hold time also is important; a change of only several seconds can sig-

nificantly affect the amount of sample ultimately delivered onto the column.

We discovered that a pulsed splitless time, using a 0.4-minute pulse at 30psi

(normal column backpressure is 8.8psi at 50°C), dramatically improves sam-

ple transfer onto the column. Making the pulse longer than the splitless hold

time allows excess solvent to be swept away quickly and dramatically sharpens

resolution of the early eluting Method 8270 Appendix IX compounds, such as

1,4-dioxane.

Other Conditions

After optimizing conditions in the injection port, we adjusted other analytical

conditions to deliver a fast, rugged analysis on a 0.25mm ID column. In com-

bination, a constant flow of 1.1mL/min., a short initial hold time (0.5 min.)

and a fast initial temperature ramp rate (25°C/min.) elute benzo(ghi)perylene

in 16.5 minutes. The final temperature ramp rate is a relatively slow 4°C/min.,

to better resolve benzo(b)fluoranthene and benzo(k)fluoranthene.

With all conditions optimized, the 117 target compounds in our sample are

well resolved by quantification ion in one analysis (Figure 1, page 6).

Optimized, 17-Minute GC Analysis of Semivolatiles

Using a 0.25mm ID Rtx®-5Sil MS Column

By Christopher English, Innovations Group Leader

• Excellent column for many methods, including US EPA methods 8270, 625, and 525.

• Greater on-column sample capacity, longer lifetimes than columns with thinner phase films.

• Analysis optimized for scanning mass spectrometers (ion trap or quadrupole).

acenaphthene

acenaphthylene

aniline

anthracene

azobenzene**

benzo(a)anthracene

benzo(a)pyrene

benzo(b)fluoranthene

benzo(ghi)perylene

benzo(k)fluoranthene

benzyl alcohol

benzyl butyl phthalate

bis 2-ethylhexyl adipate

bis(2-chloroethoxy)methane

bis(2-chloroethyl)ether

bis(2-chloroisopropyl)ether

bis(2-ethylhexyl)phthalate

4-bromophenyl phenyl ether

carbazole

4-chloroaniline

4-chloro-3-methylphenol

2-chloronaphthalene

2-chlorophenol

4-chlorophenyl phenyl ether

chrysene

dibenzo(a,h)anthracene

dibenzofuran

1,2-dichlorobenzene

1,3-dichlorobenzene

1,4-dichlorobenzene

2,4-dichlorophenol

diethyl phthalate

dimethyl phthalate

2,4-dimethylphenol

1,2-dinitrobenzene

1,3-dinitrobenzene

1,4-dinitrobenzene

4,6-dinitro-2-methylphenol

2,4-dinitrophenol

2,4-dinitrotoluene

2,6-dinitrotoluene

di-

-butyl phthalate

di-

-octyl phthalate

diphenylamine***

fluorene

fluoranthene

hexachlorobenzene

hexachlorobutadiene

hexachlorocyclopentadiene

hexachloroethane

indeno(1,2,3-cd)pyrene

isophorone

1-methylnaphthalene

2-methylnaphthalene

2-methylphenol

3-methylphenol

4-methylphenol

naphthalene

2-nitroaniline

3-nitroaniline

4-nitroaniline

nitrobenzene

2-nitrophenol

4-nitrophenol

N-nitrosodimethylamine

N-nitroso-di-

-propylamine

pentachlorophenol

phenanthrene

phenol

pyrene

pyridine

2,3,4,6-tetrachlorophenol

2,3,5,6-tetrachlorophenol

1,2,4-trichlorobenzene

2,4,5-trichlorophenol

2,4,6-trichlorophenol

*3-methylphenol and 4-methylphenol concentration is

500µg/mL.

**1,2-diphenylhydrazine (8270-listed analyte) decomposes to

azobenzene (mix component).

***N-nitrosodiphenylamine (8270-listed analyte) decomposes to

diphenylamine (mix component).

8270 MegaMix™

(76 components)

1,000µg/mL each in methylene chloride, 1mL/ampul*

cat. # 31850