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ISC 2018

32nd International Symposium on Chromatography

Restek at ISC 2018
Restek at ISC 2018

RESTEK TECHNICAL POSTERS

Monday, September 24 (12:15-13:45)
PS-01-17  Gas Chromatographic Computer Modeling Software for Optimized Method Development
Jaap de Zeeuw (presenter), Becky Wittrig, Chris Nelson, Kristi Sellers
Restek Corporation
For more information, email Jaap de Zeeuw.
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Our recently introduced modeling software is a selectivity tool that relies on a pre-loaded library of thermodynamic retention indices. This makes it possible to predict retention times and optimize chromatographic methods without the need to analyze compound sets under many different conditions. The program allows the user to select the stationary phase and simultaneously adjust: film thickness, temperature, column length, column internal diameter, and flow. Users can enter each compound or cut/paste large lists of compounds into the program.

Since its introduction there have been thousands of searches across a broad range of compound classes. The software outputs provides compound retention time, resolution, and peak width, along with the column conditions and dimensions. A model chromatogram is provided to illustrate retention, peak width, and resolution. Users have the option to view compound mass spectral data with the added benefit of overlaying mass spectra for coeluting analytes. Specific searches can be saved and accessed at a later date. Examples of these features will be presented with a focus on challenging separations.

PS-01-29  New GC Inlet Liner Deactivation Exhibits Excellent Response for Active Compounds
Jaap de Zeeuw
Restek Corporation
For more information, email Jaap de Zeeuw.
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The choice of an inlet liner is critical to GC analysts, as it can have a large impact on the quality of chromatography and the data generated. Inertness is one of the most important factors to consider, since active analytes can easily be degraded or adsorbed within a hot GC inlet. A new liner deactivation was developed with a high level of inertness towards sensitive compounds; this performance is consistent and reproducible from lot to lot and applied in the Topaz series of liners. This liner deactivation was tested with a variety of pesticides, including organochlorine, organophosphorus, and organonitrogen classes. Other liner deactivations were also analyzed to compare performance for active compounds. All test liners were single taper with wool used in splitless mode, as this provides one of the most rugged assessments of deactivation quality.

PS-05-01  Using Free, High-Performance, Computer Modeling Software to Simulate Gas Chromatographic Separations
Jaap de Zeeuw
Restek Corporation
For more information, email Jaap de Zeeuw.
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A recently developed, free to use, web-based computer program has been employed to accelerate gas chromatography (GC) method development by direct simulation of the chromatographic process. The program makes use of a highly accurate time-summation modeling approach, coupled with large libraries of data to provide absolute retention time predictions within 1% of those obtained by experiment.

The user is able to directly control every parameter of the chromatography being modeled including carrier gas, stationary phase, column dimensions, and temperature program. The temperature program can be iteratively optimized to obtain the desired separation in the minimum run time. The software is preloaded for modeling more than 20 different stationary phases and hundreds of compounds including, pesticides, PCBs, PAHs, semivolatiles, and volatile organics.

These GC modeling features allow users to develop new applications as well as visualize the impact of changing conditions, without purchasing any GC column or finding an available gas chromatograph.

Tuesday, September 25 (12:15-13:45)
PS-07-09  HILIC, Polar, and Shape Selectivity of a FluoroPhenyl Phase
Ty Kahler (presenter), Becky Wittrig, Olivier Griffaton, Sue Steinike
Restek Corporation
For more information, email Ty Kahler.
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The FluoroPhenyl stationary phase has long been marketed as a phase that offers alternative, or orthogonal, selectivity to a C18. The FluoroPhenyl phase offers unique selectivity by incorporating strongly electronegative fluorine atoms on a phenyl ring. In addition to the traditional reversed-phase dispersive interactions, this phase also exhibits shape selective, polar, cation-exchange, and even HILIC retention mechanisms which aid in selectivity of specific analytes.

In this presentation, we aim to demonstrate the useful and alternate retention of the FluoroPhenyl stationary phase. We chose several relevant target analytes which we plan to use to exemplify the unique retention characteristics of the FluoroPhenyl phase when used in either HILIC or reversed-phase mode. All of these analytes have been pursued due to either poor retention, poor resolution, or both on a traditional C18 phase.

PS-08-03  A Novel Solution for EtG/EtS Analysis in Urine by LC-MS/MS
Becky Wittrig (presenter), Justin Steimling, Ty Kahler, Frances Carroll, Olivier Griffaton
Restek Corporation
For more information, email Becky Wittrig.
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Ethyl glucuronide (EtG) and ethyl sulfate (EtS) are unique biomarkers of alcohol use. The analysis of EtG and EtS offers many advantages for abstinence monitoring including the detection window (~3 days), stability in stored specimens (nonvolatile), and specificity. EtG and EtS are both polar, which makes them difficult to retain via reversed-phase chromatography. Both compounds are also very sensitive to matrix interferences which can result in being unable to achieve low limits of detection. Isobaric interferences can also make quantitation impossible. In this study, a simple dilute-and-shoot method was developed, validated, and applied to patient samples for the analysis of EtG and EtS in human urine by LC-MS/MS enabled by the use of the novel Raptor EtG/EtS column.

Tuesday, September 25 (15:30-16:45)
PS-07-08  Affecting Selectivity and HILIC Retention on a FluoroPhenyl Stationary Phase
Ty Kahler (presenter), Becky Wittrig, Olivier Griffaton, Sue Steinike
Restek Corporation
For more information, email Ty Kahler.
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In this study we have set out to explore the retention mechanisms of the FluoroPhenyl stationary phase. The FluoroPhenyl phase may be described as having mixed-mode and/or HILIC retention and selectivity. This HILIC and mixed-mode ability results in retention mechanisms that vary, or are orthogonal to, typical reversed-phase columns, such as C18s. These chemical interactions are generally not well understood or easily demonstrated, which may be frustrating and leave chromatographers not using the phase to its fullest potential.

The FluoroPhenyl phase offers unique selectivity by incorporating strongly electronegative fluorine atoms on a phenyl ring. In addition to traditional reversed-phase dispersive interactions, this phase may exhibit polar, cation-exchange, and HILIC retention. Our focus in this presentation is on method changes including temperature, mobile phase composition, and acid strength and concentration and how these changes affect the selectivity of targeted analytes. By demonstrating the influence of method changes on this phase we aim to gather a better understanding of the interactions provided by the FluoroPhenyl phase and its use as a HILIC or mixed-mode phase.

PS-07-24  Techniques for Optimizing GC Analysis of Glycols in an Aqueous Matrix
Jaap de Zeeuw (presenter), Becky Wittrig, Corby Hilliard, Kristi Sellers
Restek Corporation
For more information, email Jaap de Zeeuw.
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The analysis of ethylene glycol in water is a common test performed by food safety, chemical, and environmental laboratories. Many environmental samples originate from water runoff at airports, where ethylene glycol is used as a de-icing agent for airplanes during winter months. Because ethylene glycol is highly soluble in water, it is not easily concentrated by purge and trap. Therefore, the most frequently used sample introduction technique is direct aqueous injection. The direct aqueous injection of ethylene glycol is challenging because it can be difficult to attain reproducibility and good peak shape. The large expansion volume of water can cause backflash, carryover can cause inconsistent results, and excess water can extinguish the FID flame. These problems can prevent achieving the detection limit for ethylene glycol, which may vary in the 1-10 ppm range. This study compares lifetimes of various PEG (polyethyleneglycol) stationary phases under optimized conditions.

PS-08-02  A Simple Method for the Analysis of Methylmalonic Acid in Human Plasma by LC-MS/MS
Becky Wittrig (presenter), Justin Steimling, Ty Kahler, Frances Carroll, Olivier Griffaton
Restek Corporation
For more information, email Becky Wittrig.
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Vitamin B12 deficiency can manifest itself in a wide variety of physical and behavioral signs and symptoms. A specific marker for diagnosing vitamin B12 deficiency is methylmalonic acid (MMA). In a part of the metabolic cycle for energy production, vitamin B12 promotes the conversion of methylmalonyl CoA to succinyl CoA. If there is not enough B12 available, blood levels of MMA begin to rise. The MMA test typically requires extensive sample pre-treatment incorporating liquid-liquid extraction, derivatization, solvent evaporation, and/or SPE. Additionally, chromatographic resolution can be difficult to achieve between MMA and its naturally occurring isomer, succinic acid. Herein, we present a simple sample preparation method without derivatization, which allows for the direct injection of protein crash supernatant while still maintaining resolution in a 5-minute cycle time.

PS-08-04  Bile Acid Profiling and Quantification in Human Plasma Using LC-MS/MS
Olivier Griffaton (presenter), Dan Li, Frances Carroll, Ty Kahler, Becky Wittrig
Restek Corporation
For more information, email Olivier Griffaton.
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Bile acids are a group of major catabolic products of cholesterol. They are important biomarkers for signaling potential harmful side effects for new drug development. There are two main types of bile acids according to their functional groups; the first is free bile acids, or unconjugated bile acids, and the second is the conjugated bile acids (primarily either glycine- or taurine-bounded). Quantitation of bile acids in matrices proves to be very challenging due to a number of factors, including the similarity of structures, varying polarities and stereochemistries, the presence of isomers, limited fragmentation for unconjugated bile acids in mass spectrometer, high endogenous levels in matrices, and matrix effects caused by phospholipids or triglycerides.

Wednesday, September 26 (15:30-16:45)
PS-12-06  Achieving Fast, Efficient Separations in Environmental Applications Using Superficially Porous Particle Column Technology
Becky Wittrig (presenter), Ty Kahler, Olivier Griffaton, Mike Chang
Restek Corporation
For more information, email Becky Wittrig.
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Superficially porous particles (SPP) 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. When combined with highly selective stationary phases, the result is significant improvements in efficiency and sensitivity over fully porous particles (FPP) of similar dimension. With Raptor LC columns, Restek chemists became the first to combine the speed of superficially porous particles (SPP) with the resolution of highly selective USLC technology. This new breed of chromatographic column allows you to more easily achieve peak separation and faster analysis times without expensive UHPLC instrumentation. The versatility of these columns makes them ideal for separations for a variety of environmental applications.

The performance of SPP particle columns will be demonstrated on a variety of applications, including bisphenol A, pesticides, and perfluorinated alkyl acids using simple mobile phases and gradient methods. For example, in order to analyze large lists of compounds, especially across multiple classes, your column must be capable of spreading analytes out over the gradient to ensure accurate detector response and quantitation. In designing the Raptor ARC-18 column, we adjusted our bonding procedures to form an ideal ligand density that offers balanced retention for the rapid analysis of large, multiclass assays. With its balanced retention profile, the Raptor ARC-18 column is ideally suited to analyze a 204-compound pesticide screen in just 9.5 minutes

Restek LC columns offer the speed of superficially porous particles with the resolution of the highly selective stationary phases, allowing peak separation and faster analysis times to be achieved without expensive UHPLC instrumentation.

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Restek at ISC 2018