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.

Analysis of Pesticides and Mycotoxins in Cannabis Brownies

Author: Nathaly Reyes and Colton Myers

Published By: Restek Corporation

Year of Publication: 2020

Link: https://www.restek.com/Technical-Resources/Technical-Library/Foods-Flavors-Fragrances/fff_FFAN3149-UNV

Abstract: Government regulations in California require the cannabis industry to test edible products for an extensive list of pesticides and mycotoxins. Here, an effective workflow for this complex analysis was developed in brownies and optimization strategies are detailed in order to provide a starting point for similar matrices. Both LC-MS/MS and GC-MS/MS were employed and excellent results for LOQ, linearity, accuracy, and precision were attained for all the target compounds.

Phospholipid and Protein Removal in One Simple SPE Process Prevents Matrix-Based Signal Suppression

Published By: Restek Corporation

Year of Publication: 2020

Link: https://www.restek.com/Technical-Resources/Technical-Library/Clinical-Forensic-Toxicology/gen_GNAR3124-UNV

Abstract: Biological samples contain proteins and phospholipids that can interfere with LC-MS/MS analysis and increase the frequency of instrument maintenance. Here we used Resprep PLR SPE to simultaneously remove proteins and phospholipids from plasma in one high-efficiency sample preparation process. Concurrent phospholipid removal eliminated signal suppression and excellent recoveries were obtained for a wide range of chemical classes without the need for additional method development.

Fast, Low-Solvent Analysis of Cannabinoids Increases Lab Productivity and Decreases Solvent Costs

Published By: Restek Corporation

Year of Publication: 2019

Link: https://www.restek.com/Technical-Resources/Technical-Library/Foods-Flavors-Fragrances/fff_FFSS3123-UNV

Abstract: Suitable for high-throughput cannabis testing labs, this LC-UV method reliably separates 19 cannabinoids in a quick, 10-minute analysis. Using only 3 mL of acetonitrile per run, labs can significantly decrease solvent use and the associated costs by adopting this procedure.

Improve Acrylamide Analysis with a Long-Lasting LC Column and a Cost-Effective Internal Standard

Published By: Restek Corporation

Year of Publication: 2019

Link: https://www.restek.com/Technical-Resources/Technical-Library/Foods-Flavors-Fragrances/fff_FFAR3126-UNV

Abstract:The porous graphitized carbon (PGC) columns typically used for acrylamide analysis by method EN 16618.2015 provide adequate retention of acrylamide and sufficient separation from matrix components, but they are subject to short column lifetimes and the need for extensive sample preparation. Here, we demonstrate an approach using an Allure Acrylamide LC column and deuterated internal standard that provides faster total analysis times and meets system suitability requirements longer, allowing labs to significantly increase sample throughput.

A Study of the Re-Equilibration of Hydrophilic Interaction Columns with a Focus on Viability for Use in Two-Dimensional Liquid Chromatography

Author (s) : Claudia Seidl12, David S. Bell3, Dwight R. Stoll1
1. Gustavus Adolphus College,  2. Universidade de São Paulo,  3. Restek Corporation

Published By: Journal of Chromatography A

Year of Publication: 2019

Volume, Issue: Vol. 1604

Link: https://doi.org/10.1016/j.chroma.2019.460484

Abstract:  In recent years there has been increasing interest in the use of HILIC separations in two-dimensional liquid chromatography (2D-LC), mainly because the selectivity of HILIC separations complement that of reversed-phase separations for a variety of molecules. Historically, the re-equilibration of HILIC phases following gradient elution has been perceived as too slow to be useful in the second dimension of 2D-LC separations in particular. Recent studies of re-equilibration of HILIC phases by McCalley and coworkers using a limited set of conditions showed that highly repeatable gradient separations could be obtained with re-equilibration times as short as 4.3 min [1][2]. In this study we aimed to study re-equilibration of HILIC phases under a broader set of conditions, and at much shorter re-equilibration times, in the interest of determining whether or not HILIC separations can be generally considered as a viable option for use in the second dimension of 2D-LC separations. To this end we studied the effects of mobile phase pH, buffer concentration, and preparation method, flow rate, analyte and stationary phase chemistry, column length, and re-equilibration time on retention of a variety of small molecule probe solutes following gradient elution. In general, we have found that excellent separation repeatability can be obtained with quite short (≪10 min) re-equilibration times, even when progress toward full equilibration of the column is quite slow (≫10 min). In other words, even if the stationary phase is not fully equilibrated, as long as it is partially equilibrated in a highly precise manner, highly repeatable retention times can be obtained. Higher flow rate has a positive effect on both the rate of progress toward full equilibration and the repeatability of separation. No significant, consistent effects of eluent pH or buffer concentration on repeatability of gradient separation were observed for the stationary phases studied. Excellent gradient separation repeatability was obtained with shorter columns (30 mm length) with re-equilibration times as short as 3 s. A proof-of-concept 2D-LC separation of several small molecule probes using HILIC separations in both dimensions was performed to illustrate that re-equilibration of these columns can be fast enough for HILIC columns to be considered as a viable option for the second dimension of comprehensive 2D-LC separations.

 

Get More Uptime with Restek’s Long-Life ESI Electrode for Sciex Turbo V Sources

Published By: Restek Corporation

Year of Publication: 2019

Link: https://www.restek.com/Technical-Resources/Technical-Library/General-Interest/general_GNAR3095-UNV

Abstract: The harsh environment inside an MS source takes its toll on ESI electrodes and, once they corrode, sensitivity drops, runs fail, and productivity halts while the instrument is offline for maintenance. The testing detailed here shows that Restek Long-Life ESI electrodes for Sciex Turbo V sources provide equivalent LC-MS/MS performance over significantly longer lifetimes.