Environmental Article

Superior Chromatography for Semivolatile Organics

Using the Rtx®-5Sil MS Capillary GC Column

by Robert Freeman, Environmental Innovations Chemist

Superior resolution of benzo(b)- and benzo(k)fluoranthene.
Symmetric peaks and excellent responses for phenols.
Excellent thermal stability and exceptionally low bleed.

GC/MS analytical methods for semivolatile compounds, such as U.S. Environmental Protection Agency Method 8270D and equivalent methods in other countries, cover a broad range of environmental pollutants. The target lists often include complex mixtures of acidic, basic, and neutral analytes. Further, the sample extracts often contain problematic matrix interferences. These factors, coupled with the increasing need for lower detection limits, place significant demand on the thermal stability, inertness, and efficiency of the analytical column.

Restek chemists designed the Rtx®-5Sil MS capillary column to address the challenging demands of semivolatiles analysis. Phenyl rings in the polymer backbone of the stationary phase stiffen the siloxane chain, preventing thermal breakdown and reducing bleed. The content of this aryl functionality has been adjusted so that selectivity is similar, but improved, compared to that of conventional 5% diphenyl/95%dimethyl phases. The silarylene polymer not only exhibits improved thermal stability and reduced bleed, it has increased separation for aromatic isomers benzo(b)- and benzo(k)fluoranthene — as shown in Figure 1.

Surface activity in a column is revealed by the response factors for active analytes, such as 2,4-dinitrophenol (acidic) and pyridine (basic). Most column manufacturers struggle to attain adequate responses and good peak shapes for such analytes. Our unique deactivation process for the Rtx®-5Sil MS silarylene phase assures unsurpassed inertness and excellent responses for these active analytes — note the response for 2,4-dinitrophenol in Figure 2, and for many other semivolatiles in Figure 3.

Featuring an optimized stationary phase, inherently low bleed, and proprietary deactivation, Rtx®-5Sil MS columns overcome the inherent problems associated with semivolatiles analyses. If you are performing these analyses, you can simplify life in your laboratory — rely on these new columns to help you obtain consistent results.

Figure 1 Superior resolution of benzo(b)fluoranthene, benzo(k)fluoranthene, and benzo(a)pyrene (10µg/mL).

GC_EV00900A

For conditions see Figure 3.

Figure 2 Excellent response for 2,4-dinitrophenol (10µg/mL).

GC_EV00900B

For conditions see Figure 3.

Figure 3 Total ion chromatogram for 94 semivolatile analytes (10µg/mL).

Peak

1,4-dioxane
2.33
N-nitrosodimethylamine
2.52
pyridine
C toluene
2.54
2-fluorophenol (Surr.)
2.67
phenol-d6 (Surr.)
3.30
phenol
3.99
aniline
4.00
bis(2-chloroethyl) ether
4.06
2-chlorophenol
4.09
1,3-dichlorobenzene
4.16
1,4-dichlorobenzene-d4 (IS)
4.29
1,4-dichlorobenzene
4.34
benzyl alcohol
4.35
1,2-dichlorobenzene
4.45
2-methylphenol
4.50
bis(2-chloroisopropyl) ether
4.53
a. 4-methylphenol
b. 3-methylphenol
4.56
N-nitroso-di-n-propylamine
4.67
hexachloroethane
4.69
nitrobenzene-d5 (Surr.)
4.81
nitrobenzene
4.84
isophorone
4.86
2-nitrophenol
5.08
2,4-dimethylphenol
5.16
benzoic acid
5.19
bis(2-chloroethoxy)methane
5.27
2,4-dichlorophenol
5.28
1,2,4-trichlorobenzene
5.40
naphthalene-d8 (IS)
4.59
naphthalene
5.55
4-chloroaniline
5.57
hexachlorobutadiene
5.62

Peak

4-chloro-3-methylphenol
6.11
2-methylnaphthalene
6.28
1-methylnaphthalene
6.38
hexachlorocyclopentadiene
6.45
2,4,6-trichlorophenol
6.57
2,4,5-trichlorophenol
6.61
2-fluorobiphenyl (Surr.)
6.66
2-chloronaphthalene
6.79
2-nitroaniline
6.90
1,4-dinitrobenzene
7.04
dimethyl phthalate
7.09
1,3-dinitrobenzene
7.12
2,6-dinitrotoluene
7.15
1,2-dinitrobenzene
7.21
acenaphthylene
7.23
3-nitroaniline
7.34
acenaphthene-d10 (IS)
7.39
acenaphthene
7.42
2,4-dinitrophenol
7.44
4-nitrophenol
7.51
2,4-dinitrotoluene
7.58
dibenzofuran
7.60
2,3,5,6-tetrachlorophenol
7.69
2,3,4,6-tetrachlorophenol
7.73
diethyl phthalate
7.84
4-chlorophenyl phenyl ether
7.96
fluorene
7.97
4-nitroanaline
7.99
4,6-dinitro-2-methylphenol
8.02
N-nitrosodiphenylamine
(diphenylamine)
8.09
1,2-diphenylhydrazine
(as azobenzene)
8.13
2,4,6-tribromophenol (Surr.)
8.22

Peak

4-bromophenyl phenyl ether
8.49
hexachlorobenzene
8.56
pentachlorophenol
8.77
phenanthrene-d10 (IS)
8.97
phenanthrene
9.00
anthracene
9.05
carbazole
9.22
di-n-butyl phthalate
9.59
fluoranthene
10.27
benzidine
10.41
pyrene-d10 (Surr.)
10.50
pyrene
10.52
p-terphenyl-d14 (Surr.)
10.52
3,3′-dimethylbenzidine
10.67
butyl benzyl phthalate
11.19
bis(2-ethylhexyl) adipate
11.20
3,3′-dichlorobenzidine
11.27
bis(2-ethylhexyl) phthalate
11.82
benzo(a)anthracene
11.86
chrysene-d12 (IS)
11.88
chrysene
11.91
di-n-octyl phthalate
12.72
benzo(b)fluoranthene
13.31
benzo(k)fluoranthene
13.36
benzo(a)pyrene
13.81
perylene-d12 (IS)
13.91
dibenzo(a,h)anthracene
15.65
indeno(1,2,3-cd)pyrene
15.68
benzo(ghi)perylene
16.10

GC_EV00900
Column:	Rtx®-5Sil MS, 30m, 0.25mm ID, 0.25µm (cat.# 12723)
Sample:	US EPA Method 8270D mix: 8270 MegaMix® (cat.# 31850), Benzoic Acid (cat.# 31879), 8270 Benzidines Mix (cat.# 31852), Acid Surrogate Mix (4/89 SOW) (cat.# 31025), Revised B/N Surrogate Mix (cat.# 31887), 1,4-Dioxane (cat.# 31853), SV Internal Standard Mix (cat.# 31206)
Inj.:	1.0µL, pulsed splitless, 10µg/mL each component, int. stds. 20µg/mL (10ng or 20ng on column), 4mm Drilled Uniliner® inlet liner, hole on bottom (cat.# 20756), pulse: 30psi @ 0.4 min.; 60mL/min. @ 0.3 min.
GC:	Agilent 6890
Inj. temp.:	250°C
Carrier gas:	helium
Flow rate:	1.2mL/min., constant flow
Oven temp.:	50°C (hold 0.5 min.) to 290°C @ 23°C/min., to 325°C @ 6°C/min. (hold 0.5 min.)
Det.:	Agilent 5973 GC/MS
Transfer temp.:	280°C
Scan range:	35-550 amu
Solvent delay:	2.20 min.
Tune:	DFTPP
Ionization:	EI