Going to ISCC & GCxGC in Fort Worth this year? Don’t miss these presentations by Restek’s expert chromatographers. Stop by our booth or attend a presentation—we’re excited to share our research and discuss solutions to your toughest chromatography challenges!
GC-MS Analysis of Phthalates: Comparison of GC Stationary Phase Performance
Dan Li, Rebecca Stevens, Chris English, Anzi Wang
Phthalates are ubiquitous in the environment and have attracted attention due to their potential adverse impact on human health. For this reason, detection and separation of phthalates has become a necessity. Gas chromatography is an effective approach for separating phthalates, and it can be paired with several detection techniques, including electron capture (ECD), flame ionization (FID), and mass spectrometry (MS). In this study, Pro EZGC gas chromatographic modeling software was employed to determine the optimal stationary phases and conditions for phthalate GC-MS analysis. The separation of phthalates was compared on seven different stationary phases: Rtx-440, Rxi-XLB, Rxi-5ms, Rtx-50, Rxi-35Sil MS, Rtx-CLPesticides, and Rtx-CLPesticides2 phases. In all cases, 18 EPA- and EU-listed phthalates were analyzed in less than 6 minutes. In addition, an extended list of 37 phthalates was analyzed in less than 40 minutes using an optimized method. Both Rtx-440, which is unique to Restek, and Rxi-XLB columns showed the best resolution of the complex phthalate mixture.
Evaluating Mass Overload on Superficially Porous Particles
Edward G. Franklin, C. Vernon Bartlett, Justin Steimling, Ty Kahler
Superficially porous particles (SPP) are a powerful analytical tool for achieving fast LC analyses. The solid, impermeable core present in these particles increases the column efficiency by decreasing the diffusion path. However, the solid core also significantly reduces the surface area that is typically available in traditional fully porous materials (FPP). There is a potential concern that arises from a reduction in surface area: column loading ability. Column overloading (mass overload) occurs when the amount of material injected onto the column exceeds the available active sites of the stationary phase. The purpose of this study was to evaluate a series of analytes and determine the effects the solid core has on the loading ability of superficially porous particles.
Affecting Selectivity and HILIC Retention on a FluoroPhenyl Stationary Phase
Vernon Bartlett, Edward G. Franklin, Frances Carroll, Shun-Hsin Liang, Sharon Lupo, Ty Kahler
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. HILIC and mixed-mode capabilities offer retention mechanisms that vary, or are orthogonal to, typical reversed-phase columns like C18s. These chemical interactions are generally not well understood or easily demonstrated, which may be frustrating and leave chromatographers not using the phase to the 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 exhibits polar, cation-exchange, and HILIC retention mechanisms. Our focus in this presentation is on method changes, including temperature, mobile phase composition, 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.
Visit the ISCC & GCxGC website. (Link “visit” to https://www.isccgcxgc.com/)
Visit www.restek.com/events to view our 2017 events calendar.
We hope you will visit us at one of these events!
Mike Shuey, Restek’s International Customer Service Supervisor, received the 2016 ESOP Outstanding Chapter Officer Award at The ESOP Association (TEA) Awards Banquet earlier this year. Mike was selected from a field of over 100 ESOP chapter officers for his significant contributions to TEA. As PA/DE chapter officer, Mike leads the legislative advocacy committee, manages the chapter advocacy web site, and coordinates ESOP education not only for other chapter members but also for members of Congress. He is also responsible for generating legislative officer goals for the year and seeing they are met to the best of his ability. Mike takes great pride in being a part of legislative efforts to support and educate our representatives to keep our ESOP benefits in place and is proud of Restek’s grass roots efforts to show the nation that our ESOP model works and is a positive business strategy for the success of our country.
On November 16–17, Separation Science will again host Food Science 2016 in Singapore. This world-class international conference and exhibition covers key food analysis topics including safety, traceability, authenticity, and ingredients analysis. Restek invites you to attend the show at a special discounted rate. In addition to Jaap de Zeeuw’s presentation, you may attend over 30 other talks on food analysis, quality, and safety.
To secure your discounted rate, register here using RESTEKSAVER as the promo code.
While you’re the Food 2016 conference, be sure to stop by Booth 112 and visit your local Restek representative, Lab Science Solution. There will be games, giveaways, and information on Restek products and solutions!
Wednesday, November 16
Reduce Analysis Time and Optimize GC Separations in Food Analysis, while Maintaining the Same Peak Elution Order: A New Free Software Tool in GC—the EZGC Method Translator
Jaap de Zeeuw, Restek Corporation
In gas chromatography, there is often a need to optimize separations using different column dimensions, linear gas velocities, detectors, or carrier gases. If you want to get the same peak elution order (same chromatogram), you must make sure that the elution temperatures of the components are kept the same. This can only be done by using a different oven temperature program. To calculate this program, there are free calculation programs available on the web. In this course, we will discuss the details of method conversion using Restek’s EZGC method translator so that you get the same chromatograms with the new method. The course will also cover how existing separations can easily be checked and corrected for optimal separation.
Shoot-and-Dilute GC-MS/MS: Use of Split Injection for Pesticide Residue Screening to Prolong GC Inlet Liner and Column Performance
Jaap de Zeeuw, Julie Kowalski, and Jack Cochran, Restek Corporation
Shoot-and-dilute GC-MS/MS uses split injection for GC paired with a very sensitive triple quadrupole mass spectrometer. Split injection can alleviate matrix-related issues that occur at the GC inlet and column. There are well-known problems associated with splitless injection of dirty samples, most notably compound degradation and drastic response changes. This can occur very quickly with real samples, sometimes with a single injection of a particularly dirty sample. Inlet and column maintenance are needed to restore instrument performance resulting in instrument downtime. An easy way to mitigate these problems is to use split injection when possible. That is, if the limit of detection and limit of quantitation requirements are achievable using split injections at ratios of 10:1 or greater. Increased flow through the GC inlet with split injection minimizes residence time inside the inlet liner. This decreases compound degradation and maintains acceptable data quality longer, especially during dirty sample analyses.
In addition to the benefits described above, the GC oven start temperature can be higher, thus reducing overall analysis time as well as the time needed to re-equilibrate the oven. Also, split injection of the common QuEChERS solvent, acetonitrile, is easily accommodated on a nonpolar 5-type GC column, allowing symmetrical peak shapes of early eluting compounds like methamidophos, dichlorvos, and acephate. This eliminates the need for extensive initial oven temperature optimization or time-consuming solvent exchange.
Shoot-and-dilute GC-MS/MS was tested for multiclass pesticides and compared with a splitless injection method. Split injection and the initial GC oven temperature parameters were optimized. Viability of split injection based on detectability of over 200 analytes was determined in QuEChERS-prepared green bell pepper, celery, and orange. Green bell pepper cleanup using dispersive SPE without graphitized carbon black sorbent was less than ideal with a relatively high level of chlorophyll remaining in the sample, which severely stressed GC inlet performance for splitless work while the split method was much more robust. Ruggedness of split and splitless methods was evaluated by comparing average response factors and corresponding %RSDs and by showing chromatographic performance differences, especially for compounds that show degradation products.
Wool Packing or No Wool Packing in a Splitless GC Inlet Liner–Which is better for Pesticide Analysis? A Case Study with a QuEChERS Strawberry Extract
Jaap de Zeeuw and Jack Cochran, Restek Corporation
Pesticide chemists usually avoid glass wool packing for splitless injection GC because sometimes lower responses are seen for active or thermally unstable pesticides (e.g., carbaryl, DDT, iprodione, etc.) However, properly deactivated quartz wool is not only a valuable protector of the GC column from nonvolatile “dirt,” but it also offers increased responses for pesticides because it stops them from hitting the bottom seal in a typical GC inlet where they can be lost or degraded.
This study compared GC-MS response factors for a group of pesticides ranging in volatility and class (organochlorine, organonitrogen, organophosphorus, carbamate, and pyrethroid) that were fortified into a QuEChERS strawberry extract. The extract was then splitless injected into single taper liners with wool and without wool. The initial response factors were higher for the wool-packed inlet liner versus the liner without wool. After 60 analyses of strawberry extract on each liner, some of the more difficult pesticides showed lower response factors on both liner types, but overall the wool-packed liner still showed higher response factors than the liner with no wool.
A final part of the study compared response factors for deactivated quartz wool liner packing to deactivated borosilicate wool liner packing. Deactivated quartz wool was significantly better for analyzing dimethoate, chlorothalonil, carbaryl, methiocarb, dicofol, and deltamethrin.
For more event information, visit the Food Science 2016 conference page.