There is No Time to Waste: Low-Pressure Gas Chromatography–Mass Spectrometry is a Proven Solution for Fast, Sensitive, and Robust GC–MS Analysis

Author(s): Steven J. Lehotay2, Jaap de Zeeuw1, Yelena Sapozhnikova2, Nicolás Michlig2,3, Jana Rousova Hepner1, and Joseph D. Konschnik1

1. Restek Corporation, 2. Eastern Regional Research Center at the U.S. Department of Agriculture, 3. Programa de Investigación y Análisis de Residuos y Contaminantes Químicos (PRINARC), in the Facultad de Ingeniería Química at the Universidad Nacional del Litoral

Published By: LCGC North America 38(8)

Year of Publication: 2020

Link: https://cdn.sanity.io/files/0vv8moc6/chroma/f562afa926baa1c61c935270836a3374f513bb14.pdf#page=33

Abstract: Low-pressure gas chromatography (LPGC) has been known to be advantageous compared to standard GC since Giddings first described the concept in 1962, but a practical solution for its use eluded analytical chemists until the year 2000, when de Zeeuw fashioned a simple guard column restrictor concept to maintain positive inlet pressure for a wide-bore analytical column under vacuum. Initially introduced as rapid mass spectrometry (MS), de Zeeuw’s invention made LPGC practical in nearly any GC application using MS for detection. Lehotay and associates have demonstrated the advantageous features, excellent performance, and practical utility of LPGC–MS in dozens of publications since 2001. In our experience, LPGC–MS is the most practical and beneficial fast-GC technique available to achieve <10 min analyses in applications that typically take 20–40 min. Sample capacity and column robustness are increased greatly using LPGC to permit large-volume injection with standard inlets without column maintenance, and, because vacuum conditions generate taller and narrower peaks that are still suitable for standard MS data acquisition rates, sensitivity is also increased. Furthermore, enhanced selectivity of detection using modern MS tools and software compensate for reduced chromatographic peak capacity. In our view, LPGC–MS should be the first option for evaluation in many GC–MS applications to provide fast, sensitive, and robust analyses.

Automated Inline Pigment Removal for the Analysis of Pesticide Residues in Spinach by Liquid Chromatography Tandem Mass Spectrometry

Author(s): Sharon A. Lupo, Randall L. Romesberg, Xiaoning Lu
Restek Corporation

Published By: Journal of Chromatography A

Year of Publication: 2020

Link: https://www.sciencedirect.com/science/article/pii/S0021967320307470

Abstract: An automated inline sample preparation (ILSP) method has been developed for pesticide residue analysis in spinach by LC-MS/MS. Chlorophyll pigments and other matrix constituents were removed from the sample extract using a UHPLC system equipped with an auxiliary pump, 6-port high pressure switching valve, and dual-directional ILSP cartridge containing bonded silica. The new procedure was evaluated as an entirely separate workflow using a simple solid-liquid extraction and as part of a cleanup strategy in conjunction with QuEChERS. Accuracy and precision experiments were conducted in spinach at two concentration levels (n=6). Of the 63 pesticides tested, 86% (0.005 mg/kg) and 100% (0.05 mg/kg) displayed average recoveries within 70-120% and RSD values ≤20% for the ILSP method. In addition, low to moderate matrix effects (<50%) were calculated for 95% of the analytes. Overall performance of the proposed method was found to be better or comparable to a traditional QuEChERS procedure utilizing AOAC formulated salts and dSPE sorbents, while significantly reducing the amount of pigments reaching the MS source. The ILSP workflow is a simpler procedure with fewer steps that require less time than traditional extraction and cleanup techniques.

Routine LC Maintenance: Simple Steps to Preventing Unexpected Downtime

Published By: Restek Corporation

Year of Publication: 2020

Link: https://www.restek.com/Technical-Resources/Technical-Library/General-Interest/general_GNAR3214-UNV

Abstract: Routine LC maintenance will keep your instrument performing well and minimize downtime for unexpected repairs. In this article, we explore how to develop an effective preventative maintenance plan.

Novel Stationary Phase for Comprehensive PFAS Analysis: Ultrashort-Chain (C2, C3), Alternative, and Legacy Compounds

Published By: Restek Corporation

Year of Publication: 2020

Link: https://www.restek.com/Technical-Resources/Technical-Library/Environmental/env_EVFA3197A-UNV

Abstract: In this fast, isocratic LC-MS/MS analysis, Raptor Polar X columns provide proper chromatographic retention of TFA and other small, polar ultrashort-chain PFAS as well as short- and long-chain PFAS.

Simple Large Volume Injection Method for Trace-Level Glyphosate in Bottled Drinking Water

Published By: Restek Corporation

Year of Publication: 2020

Link: https://www.restek.com/Technical-Resources/Technical-Library/Environmental/env_EVFA3196-UNV

Abstract: Trace-level detection of glyphosate can be achieved without complex derivatization or ion paining by using direct large volume injection of water on a Raptor Polar X column.

Raptor Polar X: Separate a Wide Variety of Polar Analytes with a Novel Hybrid Stationary Phase

Published By: Restek Corporation

Year of Publication: 2020

Link: https://www.restek.com/Technical-Resources/Technical-Library/General-Interest/gen_GNSS3195-UNV

Abstract: The unique hybrid phase in Raptor Polar X columns balances HILIC and ion exchange retention modes, making it ideal for analyzing a wide range of polar compounds, especially when coupled with mass spectrometry.

Sputtered Silicon Solid Phase Microextraction Fibers with a Polydimethylsiloxane Stationary Phase with Negligible Carry-Over and Phase Bleed

Authors: Tuhin Roychowdhury2,  Dhananjay Patel2, Dhruv Shaha2, Anubhav Diwan3, Massoud Kaykhaii4,
Jason Herrington1, David  Bell1,  Matthew Linford2

1. Restek Corporation, 2. Department of Chemistry & Biochemistry, Brigham Young University, 3. Moxtek, Inc.,
4. Department of Chemistry, Faculty of Sciences, University of Sistan and Baluchestan

Published By: Journal of Chromatography A

Year of Publication: 2020

Link: https://doi.org/10.1016/j.chroma.2020.461065

Abstract:
We report the preparation of high performance, sputtered, polydimethylsiloxane (PDMS)-coated solid phase microextraction (SPME) fibers that show negligible carry-over and phase bleed. This process involves sputtering silicon onto silica fibers and functionalizing the resulting porous nanostructures with ultrathin films of vapor-deposited PDMS. Different thicknesses of silicon (0.25, 0.8, and 1.8 µm) and PDMS (8, 16, and 36 nm) were produced and their extraction efficiencies evaluated. The deposition of PDMS was confirmed by time-of-fight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), and contact angle goniometry on model, planar silicon substrates. These fibers were investigated using direct immersion SPME coupled with gas chromatography-mass spectrometry (GC-MS) analysis of a series of polycyclic aromatic hydrocarbons (PAHs), which are carcinogenic pollutants. The 1.8 µm thick silicon coating with 16 nm of PDMS (Si (1.8 µm)/PDMS (16 nm)) produced the best response among the combinations tested. Conditions for the extraction of PAHs with this fiber were optimized and its extraction performance was compared to that of a commercial 7 μm PDMS fiber. The linearity (1 – 110 µgL−1), repeatability (RSD%, n=3) (17% ave.), and minimum detection limits (0.6 – 1.5 µgL−1) of the sputtered fibers were determined and found to be superior to the commercial 7µm PDMS fiber in many respects. Carry-over and phase bleed from commercial PDMS-based SPME fibers are two of their major drawbacks, which decrease their lifetimes and usefulness. Minimal carry-over and phase bleed were observed for our sputtered PDMS-coated fibers. In particular, our fiber only shows 12 % of the phase bleed of the comparable commercial fiber. In addition, it shows no carry-over for analytes with retention times greater than pyrene, and only 5 % of the carry-over of the other analytes. Our fibers could be used for at least 300 injections without any significant loss of performance.

Hunting Molecules in Complex Matrices with SPME Arrows: A Review

Author(s): Jason Herrington, German Gómez-Ríos, Colton Myers, Gary Stidsen, David Bell
Restek Corporation

Published By: Separations

Special Issue: Development of Alternative Green Sample Preparation Techniques

Year of Publication: 2020

Link: https://doi.org/10.3390/separations7010012

Abstract:
Thirty years since the invention and public disclosure of solid phase microextraction (SPME), the technology continues evolving and inspiring several other green extraction technologies amenable for the collection of small molecules present in complex matrices. In this manuscript, we review the fundamental and operational aspects of a novel SPME geometry that can be used to “hunt” target molecules in complex matrices: the SPME Arrow. In addition, a series of applications in environmental, food, cannabis and forensic analysis are succinctly covered. Finally, special emphasis is placed on novel interfaces to analytical instrumentation, as well as recent developments in coating materials for the SPME Arrow.

LC-MS/MS Analysis of Acrylamide in Drinking Water Using Large Volume Injection

Published By: Restek Corporation

Year of Publication: 2020

Link: https://www.restek.com/Technical-Resources/Technical-Library/Environmental/env_EVAR3184-UNV

Abstract: In this work, we share a method for the analysis of acrylamide in drinking water at low ppt levels using large volume injections directly into an LC-MS/MS.

Tips for Preparing Calibration Curve Standards and Avoiding Sources of Error

Author: Landon Wiest

Published By: Restek Corporation

Year of Publication: 2020

Link: https://www.restek.com/Technical-Resources/Technical-Library/General-Interest/gen_GNAR3169-UNV

Abstract: When preparing calibration curve standards, minimizing sources of error is vital for obtaining accurate quantitative results. This article shares best practices relating to equipment, chemical interactions, and workflow solutions that will help ensure accurate and precise analytical results.