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Environmental
GC/MS Low-Level for Semivolatiles in DrinkingWater /
Excellent Responses at lang On Column, Using an Rxi™-Sms Column
By Robert Freeman, Environmental Innovations Chemist
• Inert, ultra- low bleed column improves low level analyses.
• Excellent peak shapes and responses for active analytes.
• Drilled Uniliner" inlet liner minimizes sample breakdown in the injector.
Semivolatileorganic chemical contaminants in drinking water are target compounds
in many analytical methods, worldwide. US EPAMethod 525.2,for example, is a gen­
eral purpose solid-phase extraction/GC/MS procedure for identifying and quantify­
ing a wide range of semivolatile compounds. Analytes, and introduced internal stan­
dards and surrogates, are extracted from a l-liter water sample by passing the sample
through a solid phase extraction disk containing a bonded CI8 phase (e.g., Resprep'"C18, cat. #24004). Target compounds are trapped on the disk, then eluted in a small
amount of solvent. The extract is concentrated by evaporating the solvent, and the
sample components are separated, identified, and quantified by GC/MS.
As is true for many other semivolatiles methods, the extensive target compound list
for Method 525.2 encompasses numerous classes of analytes. These diverse com­
pounds present varying difficulties in the analysis, including differing modes of
degradation. Coupled with the continual need for lower levels of detection, these
challenges make extreme demands on the chromatography column, and the analysis
requires an inert, thermally stable, low-bleed stationary phase. To meet these needs,
we recommend a 30 meter, 0.25mm ID, 0.25flm RxiTM-5ms column. Enhanced surface
deactivation provides Rxi™-5ms columns with exceptional inertness and ultra-low
bleed, ensuring resolution and symmetric peaks for these difficult analytes.
Figure I shows the total ion chromatogram for 88 semivolatiles commonly analyzed
in drinking water, and listed in US EPAMethod 525.2, at lOng each on an RxiTM-5ms
column. Resolution and peak shapes are exceptionally good.
To minimize analyte degradation in the injection port, and discrimination among
analytes by molecular weight, we recommend installing a Drilled Unilinerw inlet liner
in the injection port. This liner forms a Press-Tight®seal with the inlet end of the col­
umn, eliminating contact between the sample and the hot metal surfaces in the injection
port and assuring near-complete sample transfer. The small hole in the wall of the liner
allows the liner to be used with split/splitless injections . As an additional precaution to
minimize analyte breakdown, we use a pulsed splitless injection (50psi I 0.3 min.; Iul,
sample) to reduce the time the analytes spend in the injection port.
Exceptional inertness and ultra-low bleed enable an RxiTM-5ms column to perform
exceptionally well in analyses of complex mixtures of semivolatile compounds. We rec­
ommend pairing an Rxi™-5ms column with our recently revised analytical reference
mixes for semivolatile pollutants in water, listed on page 16 of this Advantage. Restek can
provide all the materials needed for a semivolatiles analysis: extraction disks, analytical
reference materials, and a column capable of excellent responses for all target analytes at
low on-column concentrations.
Rxi™-Sms Columns (fusedsilica)
(Crossbond" 5%diphenyl / 95%dimethyl polysiloxane)
ID df (urn) temp. limits length cat # price
O.25mm Q15--=§9Jo)}Q.o~_O~~ 30-Meter 13423 $435
more •
For more information about Drilled Unifiner" inletliners see page
11and request lit cat# 59877, or visitourwebsite:
Website : E-mail : TelNo : 03 9762 2034 . . . in AUSTRALIA