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In Memorium
This issue of the Restek Buzz is dedicated to Dr. Robert L. Grob, an exceptional scientist, colleague, and friend, who passed away October 22, 2006.
Sample Preparation Techniques Used for Gas Chromatography
Guest Editorial by Robert L. Grob, Ph.D.
Sample preparation principles and techniques for gas chromatography are reviewed.
Techniques include: static headspace, dynamic headspace, solid phase extraction
and microextraction, distillation, stir bar sorptive extraction, Soxhlet, accelerated
solvent extraction, pressurized liquid extraction, subcritical water extraction,
microwave assisted extraction, ultrasonic extraction, and supercritical fluid extraction.
Analyze Biodiesel Oil for Glycerin
Using Restek's Robust Rtx®-Biodiesel Capillary GC Column
We challenged our Rtx®-Biodiesel column with analysis for glycerin in biodiesel
according to method ASTM D-6584-00. Excellent linearity was established for glycerin,
triolein, monolein, and diolein, with r2
values exceeding the method criteria for all compounds. Mono-, di-, and triglycerides
resolved well from other compounds in B100 biodiesel oil. Column performance was
strong at high temperatures, with low bleed even at 380°C. An Alumaseal™
connector and guard column were used to extend column life.
High Throughput of Semivolatiles Samples by GC/MS
Using a 20m x 0.18mm x 0.30µm Rxi™-5ms Column
We developed the 20m x 0.18mm x 0.30µm Rxi™-5ms column to balance the
demand for shorter analysis times with the need to maintain both column capacity
and column efficiency. Here we establish conditions for eluting more than 90 semivolatiles,
including 7 surrogates and 6 internal standards, in less than 12 minutes. Benzo(b)
and benzo(k)fluoranthene were resolved well and sample throughput was improved by
75%. This highly inert, low bleed column is ideal for GC/MS analysis.
Resolving Benzo(j)fluoranthene from Other PAHs
Using a Pinnacle™ II PAH Column
Nineteen polycyclic aromatic hydrocarbons (PAHs), including benzo(b) and benzo(j)fluoranthene,
were fully resolved using a Pinnacle™ II PAH column. Greater sensitivity was
achieved by coupling UV and fluorescence detection. This HPLC method offers improved
resolution compared to standard GC techniques.
Analysis of Brominated Flame Retardants on an Rxi™-5ms Column
Optimizing Method Conditions to Reliably Quantify BFRs
Brominated flame retardants are an analytical challenge because high temperatures
are required to elute them from the GC column, but elevated temperatures can also
can debrominate them, leading to extraneous peaks and poor peak shape. Excellent
resolution and peak symmetry for BDE-209 and other EPA Method 527 BFRs were achieved
using an Rxi™-5ms column below 300°C. Column bleed was low and chromatography
was excellent — even for the comprehensive Wellington mix.
Robust 9-Minute GC Analysis of Cholesterol
Excellent Sample Throughput with an Rxi™-5ms Column
Conditions are established for analyzing both derivatized and underivatized cholesterol
on a highly inert Rxi™-5ms column. Methods described include both an isothermal
analysis for use when interferences are minimal, but sample throughput is critical,
and a temperature program for use when separation of analytes from contaminants
or interfering compounds is the primary concern. Results for both derivatized and
underivatized samples were highly reproducible.
Separating NSAIDs through Aromatic Selectivity
Improve Retention by Using an Allure® Biphenyl HPLC Column
Non-steroidal anti-inflammatory drugs (NSAIDs) are typically separated on C18 phases.
Separations on our Allure® Biphenyl HPLC column are based on pi-pi interactions,
resulting in optimized retention and selectivity. Increased retention requires higher
organic content in the mobile phase, increasing desolvation efficiency in LC/MS.
Simple mobile phase changes enhance selectivity, making this column a great alternative
to conventional phenyl phase columns, especially in method development.
Reliably Confirm Cannabinoids by GC/MS
Using a 12m x 0.20mm ID 0.33µm Rxi™-5ms Column
Screening for evidence of marijuana use is typically done using an immunoassay method
to detect derivatives in urine, but confirmation of positive results requires GC/MS.
Here we describe a GC/MS method, using an Rxi™-5ms column, that resolves all
major cannabinoid metabolites to baseline and exhibits very low bleed, even at 300°C.
We also prolonged column life by baking at 340°C to remove derivatization by-products.
EZ No-Vent™ GC Column-Mass Spectrometer Connector
For Agilent, Thermo and Varian Instruments
Our EZ No-Vent™ GC column-mass spectrometer connector eliminates the need for
purge gas and allows you to skip the lengthy vent and pump down cycle usually required
when changing a column. This can save nearly a day of downtime per column change.
It is simple to use and easily attaches to the MS source without special tools or
extra plumbing. Features include an inert gold-plated body, deactivated transfer
lines to focus analytes, and high-temperature polyimide ferrules to eliminate leaks.
Peak Performers
Supplies for Agilent GC/MS Instruments
Featured items include an improved MSD conversion fitting that reduces the chance
of leaks, an MSD source nut that permits easy removal of ferrules with a tapered
needle file, an inert (gold-plated) transfer line for 5971/5972 MS systems, our
capillary installation gauge that ensures correct and consistent installation distances
and prevents crushed column ends, Alumaseal™ aluminum ferrules that do not
need re-tightening, and more.
Cool Tools
Restek Innovations Save You Time and Money
Our Inlet Liner Removal Tool lets you remove and replace the liner in a hot injector
without burning your fingers. The Wool Puller/Inserter places wool plugs correctly
and removes them easily. The Inlet Liner Packing Tool ensures reproducible positioning
of wool plugs to a specific depth.
Superior Protection Against Corrosion: Silcosteel®-CR
Treated Fittings and Tubing
Silcosteel®-CR treatment is highly effective protection for stainless steel
exposed to hydrochloric acid, nitric acid, or marine environments: in independent
tests, Silcosteel®-CR treatment upgraded the corrosion resistance of 300-grade
stainless steel by an order of magnitude. Now, electropolished stainless steel tubing
and a wide selection of world-renowned Swagelok® fittings are available with
Silcosteel®-CR treatment, from stock. Custom treatment of system components
also is available.
Restek's Knowledgeable Technical Support
Real People, Real Time and Real Results for YOU!
Restek's Technical Support group includes more than 64 individuals with extensive
experience in chemistry, chromatography, engineering, and related fields. When you
call Restek, you have access to the combined expertise of everyone in this group.
With more than 110 international distributors and dealers in 81 countries, we can
understand and respond to your lab's unique challenges whether you are in North
America, South America, Africa, Asia, Europe, the Pacific Rim or elsewhere.
These publications are available in printed form or online, as downloadable pdf files.
