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NEMC 2020 Virtual
Restek at NEMC 2020 Virtual

RESTEK LUNCHEON SEMINAR:

THURSDAY, 13 AUGUST, 12:15 p.m.
Analysis of Underivatized Glyphosate and Other Polar Contaminants
Shun-Hsin Liang
For more information, email Shun-Hsin Liang.
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The most commonly used LC retention techniques for polar compounds are HILIC and ion-exchange approaches. The Raptor Polar X is a novel phase chemistry that blends these two mechanisms on a single ligand and provides balanced retention and selectivity for a wide range of polar compounds. In this luncheon seminar, we will discuss how to implement the Polar X column for the analysis of polar contaminants, including glyphosate and ultrashort-chain per- and polyfluoroalkyl substances (PFAS), in water.

The analysis of underivatized glyphosate and its metabolites in water is challenging primarily because it is not retained on reversed-phase columns, and its response is often poor due to chelation with metal surfaces along the sample path through the LC-MS/MS system. The Polar X column shows high retention and selectivity for glyphosate, AMPA (glyphosate’s metabolite), and glufosinate, as well as other polar pesticides. On a relatively short (3 cm) column, and under the simple LC-MS conditions, these structurally related polar compounds are well separated with a retention k’ for glyphosate, AMPA, and glufosinate being about 30, 4, and 16, respectively. The unique retention mechanism of Polar X column allows large volume injection (500 µL) of drinking water, which is a very simple way to achieve low-level detection of glyphosate at 100 ppt.

Ultrashort-chain (C2 and C3) PFAS are small, and very polar compounds, including trifluoroacetic acid (TFA), perfluoropropanoic acid (PFPrA), perfluoroethane sulfonate (PFEtS), and perfluoro-propane sulfonate (PFPrS). Their ubiquitous presence in aquatic environment has become a major concern in parallel to PFAS contamination. Given the high polarity of ultrashort-chain PFAS, it is impractical to include these compounds for regular PFAS monitoring with reversed-phase LC. As demonstrated here, a simple and fast LC-MS/MS method was established for simultaneous analysis of ultrashort-chain, alternative, and legacy PFAS in water using the Polar X column.

RESTEK ORAL PRESENTATIONS:

TUESDAY, 4 AUGUST, 1:30 p.m.
Handling Interferences in Ethylene Oxide Testing in Air
Jason Hoisington
For more information, email Jason Hoisington.
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Ethylene oxide is used in the manufacture of a number of commercial products as well as being used for sterilization of equipment that can’t be exposed to steam. Based on the 2014 National Air Toxics Assessment (NATA), the EPA has identified ethylene oxide as a concern due to potential elevated cancer risks in some areas of the U.S. The analysis of ethylene oxide in air is complicated by interferences from common air contaminants such as methanol, acetaldehyde, and trans-2-butene.

This presentation shows a method for the detection of ethylene oxide using cryogenic GC to separate ethylene oxide from interfering compounds and MS with selected ion monitoring for detection at low levels. It also examines issues of background contamination when using stainless-steel canisters and lines for sampling. The results of new stainless-steel canisters are compared to fused silica lined canisters, and potential canister cleaning methods to reduce background ethylene oxide in stainless-steel are evaluated.

TUESDAY, 4 AUGUST, 2:30 p.m.
Stability of Sulfur Compounds in Whole Air Sampling
Jason Hoisington
For more information, email Jason Hoisington.
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Volatile sulfur compounds in ambient air can be a major source of odors near industrial and agricultural areas and present significant challenges for collection and analysis. Sulfur compounds such as hydrogen sulfide, methyl mercaptan, and ethyl mercaptan show higher reactivity in ambient air samples when compared to dry lab standards and can break down in air canisters and sorbent tubes. This presents difficulties in collecting accurate measurements as samples must be rushed to laboratories or analyzed on-site to guarantee good data. Surface deactivations, such as fused silica lined (FSL) canisters, have historically been used to extend the lifetime of reactive sulfurs in whole air samples, but the stability of some sulfur compounds is still limited.

This presentation investigates the effects of increasing humidity on the stability and repeatability of 6 sulfur compounds (hydrogen sulfide, carbonyl sulfide, methyl mercaptan, ethyl mercaptan, dimethyl sulfide, and dimethyl disulfide) in ambient air using GC/FPD. The differences between standard electropolished air canisters and fused silica lined canisters are also explored. Methods for drying air during sampling are also investigated, and a sampling method is proposed that limits the loss of sulfur compounds due to drying and extends sample shelf life by reducing the humidity of the collected air.

THURSDAY, 20 AUGUST, 2:00 p.m.
Novel Stationary Phase for Simultaneous Analysis of Ultrashort-Chain (C2, C3), Alternative, and Legacy PFAS
Shun-Hsin Liang
For more information, email Shun-Hsin Liang.
Read abstract

Current LC-MS/MS methods for per- and polyfluoroalkyl substances (PFAS) monitoring do not address the analysis of newly trending ultrashort-chain (C2 and C3) compounds due to their insufficient retention on typical reverse-phased columns. It is of importance to monitor these compounds for their ubiquitous occurrence in aqueous environmental samples. This presentation will discuss the LC-MS/MS method development and evaluation for C2 and C3 PFAS analysis and analytical methodologies for simultaneous chromatographic determination of C2-C8 compounds and alternative PFAS, including GenX, ADONA, and F-53B.

A reverse-phased LC method was previously established for direct injection analysis of various water samples including tap water, river water, groundwater, and sewage treatment (effluent) water for ultrashort-chain PFAS analysis. It was shown that C3 compounds, PFPrA and PFPrS, could be analyzed together with alternative and legacy PFAS with this reverse-phased methodology. However, a critical challenge was encountered for C2 or trifluoroacetic acid (TFA) analysis with the current reverse-phased LC method due to its minimum retention on the column.

Implementing a unique hybrid HILIC/ion-exchange column, a fast and easy LC method was developed for simultaneous analysis of C2, C3, C4, C6, and C8 compounds and alternative PFAS (GenX, ADONA, and F-53B). This method provides convenient setup and high throughput analysis for the lab interested in adding ultrashort-chain compounds to PFAS assay in potable and non-potable waters.

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