The 21st International Symposium on Separation Sciences (ISSS) is approaching quickly and Restek is pleased to sponsor this exciting conference. Join us June 30–July 3, 2015 in Ljubljana, Slovenia for top-notch workshops, lectures from leaders in the separation sciences, and a full social program. A plenary talk on the use of nitrogen as a carrier gas in GC will be offered by Jaap de Zeeuw. In addition, Hansjörg Majer will present posters on recent LC work at Restek. Both scientists are organizing a workshop that will be focused on simplifying method development; be sure to look for “Easy and Practical Strategies for Choosing the Optimal Column for Separating Your Target Analytes in GC and LC” in the program guide and join us for some excellent tips and tactics. Symposium attendees are also invited to visit with us at the Restek booth to discuss analytical work and participate in our Chromatography Mastermind game. Presentation abstracts are provided below.
Using Nitrogen Instead of Helium as Carrier Gas While Maintaining the Exact Same Separation Efficiency, Retention Times, and Peak Elution Order without Changing the Oven Temperature Conditions
(Jaap de Zeeuw)
For several reasons, there is interest in replacing helium with a different carrier gas in gas chromatography. Hydrogen is the obvious choice, but there are some concerns with safety and reactivity. It is also possible to use nitrogen, but this is often not considered because it has a low optimal velocity and flow rate. However, by using method translation and chromatogram modeling, it is clear that the loss of efficiency observed when using nitrogen can be perfectly compensated for by using a smaller ID capillary of a shorter length. By replacing a 30 m x 0.25 mm column with a 20 m x 0.15 mm column, identical separations can be obtained in the same analysis time when using nitrogen instead of helium–with the exact same oven programming condition. Even the inlet pressures are very close. The only price that has to be paid is a loss in loadability, which means that this concept will not work for every application, but it will be very useful for many. Besides the guaranteed availability, using nitrogen offers a big advantage in the cost and consumption volume of carrier gas, meaning cost per analysis will also benefit significantly.
A Multiclass Drug and Metabolite Screen of 231 Analytes by LC-MS/MS
(Dr. Hansjörg Majer, Frances Carroll, Sharon Lupo, Dr. Shun-Hsin Liang, Ty Kahler, Ed Frankin)
The use of pain management drugs has been steadily increasing. As a result, labs are seeing an increase in patient samples that must be screened for a wide variety of drugs to prevent drug abuse and to ensure patient safety and adherence to their medication regimen. Therapeutic drug monitoring can be challenging due to the low cutoff levels, potential matrix interferences, and isobaric drug compounds. To address these challenges, many drug-testing facilities are turning to liquid chromatography coupled with mass spectrometry (LC-MS/MS) for increased speed, sensitivity, and specificity. In this example, a method was developed for a multiclass drug and metabolite screen containing 231 compounds. Experiments addressed mobile phase considerations, sample diluent, isomer resolution, drug interferences, and instrumentation capabilities. During mobile phase investigations, it was found that methanol provided the best retention of early eluting analytes, such as morphine, oxymorphone, nicotine, and norcotinine. Sample diluent was optimized to improve the peak shape of the early eluting compounds. Scan rates and retention time windows were optimized to insure enough data points per peak were collected. The final method used an optimized separation gradient analysis time of 10 minutes with a total cycle time of 12 minutes.
Column Performance: Comparison of the Superficially Porous Particle (SPP) to the Fully Porous Particle (FPP)
(Dr. Hansjörg Majer, Sharon Lupo, Dr. Shun-Hsin Liang, Frances Carroll ,Ty Kahler)
Superficially porous particles (commonly referred to as SPP or “core-shell” particles) have been proven to provide fast and efficient separations. These particles feature a solid, impermeable core enveloped by a thin, porous layer of silica that decreases the diffusion path and reduces peak dispersion. As a result, significant improvements in efficiency and sensitivity can be achieved over fully porous particles (FPP) of similar dimension.
In this presentation, the performance of 5 µm SPP columns will be compared to columns packed with traditional 5 µm and 3 µm FPPs. The relationship between pressure and efficiency will be explored. In addition, analysis time, signal-to-noise ratio, peak width, and resolution will be evaluated in several chromatographic experiments. Each experiment will be performed on the same instrument using identical method conditions for each particle.
We will discuss the following potential advantages of 5 µm SPP columns over columns packed with traditional 5 µm and 3 µm FPPs. When used in the development of new assays, they allow the chromatographer to obtain fast analysis times and excellent method performance without changes in instrumentation. When substituted into existing methodologies that utilize 5 µm and 3 µm FPP columns, 5 µm SPP columns have the potential to dramatically decrease analysis times while improving efficiency and sensitivity.