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2005vol. 3
Restek Innovations chemistshave evaluatedmany combinationsof stationary
phase, column dimensions, and analytical conditions for analyzing environ-
mental semivolatile compounds such as those listed in US Environmental
ProtectionAgencyMethod 8270. Using a typical benchtop quadrupolemass
spectrometer,wehaveachieveda15-minuteanalysis,whilemaintaininga scan
rate of at least 5 scans per target analyte.¹ Time-of-flightmass spectrometers
(TOFMS)make analysis times under 9minutes achievable,² because they can
scanmore than100 times faster thanquadrupole instruments.
Afterdeveloping thisanalysisona0.18mm ID,0.36µmcolumn,³our chemists
decided to experiment with a column of standard ID andphase filmdimen-
sions (0.25mm ID / 0.50µm film), in an attempt to establish a similarly rapid
analysisona largerborecolumn.Thecolumn theychosewasa30mx0.25mm
ID x 0.5µm Rtx®-5Sil MS column. The target compound list included our
8270MegaMix™ andAppendix IXMix#2mixes, plus internal standards and
surrogates—a total of 117compounds.Advantagesof usinga0.25mm IDcol-
umnwith a 0.5µm phase film include increased sample capacity and longer
column lifetime, combinedwith rapid analyses.
InjectionPortOptimization
The first step in the experiment was to optimize conditions in the injection
port.We found that the inlet liner and seal remain inert longerwhenwe inject
only 0.5µL of sample into the injection port. This increases the number of
passingcalibrationchecksper linerand seal,and soreduces instrumentdown-
time. The key tomaintaining sensitivity when injecting smaller amounts of
sample is to attain themost efficient sample transfer possible: we determined
a 2mm ID inlet linermost efficiently transfers 0.5µL samples.
Splitlesshold time also is important; a changeof 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 columnbackpressure is 8.8psi at 50°C), dramatically improves sam-
ple transfer onto the column.Making the pulse longer than the splitless hold
timeallows excess solvent tobe swept awayquicklyanddramatically sharpens
resolutionof theearlyelutingMethod8270Appendix IXcompounds, suchas
1,4-dioxane.
OtherConditions
Afteroptimizing conditions in the injectionport,we adjustedother analytical
conditions todeliver a fast, rugged analysis on a0.25mm ID column. In com-
bination, a constant flow of 1.1mL/min., a short initial hold time (0.5min.)
anda fast initial temperature ramp rate (25°C/min.) elutebenzo(ghi)perylene
in16.5minutes.The final temperature ramp rate is a relatively slow4°C/min.,
tobetter resolve benzo(b)fluoranthene andbenzo(k)fluoranthene.
With all conditions optimized, the 117 target compounds in our sample are
well resolvedbyquantification ion inone analysis (Figure 1, page 6).
Optimized,17-MinuteGCAnalysisofSemivolatiles
Usinga0.25mm IDRtx®-5SilMSColumn
By Christopher English, Innovations Group Leader
• Excellent column formanymethods, includingUSEPAmethods 8270, 625, and525.
• Greater on-column sample capacity, longer lifetimes than columnswith thinner phase films.
• Analysisoptimized for scanningmass spectrometers (ion trapor 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-
n
-butyl phthalate
di-
n
-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-
n
-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).
8270MegaMix™
(76 components)
1,000µg/mL each inmethylene chloride, 1mL/ampul*
cat.# 31850
