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

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.

Comparison of extraction techniques for polycyclic aromatic hydrocarbons from lichen biomonitors

Author(s): Leandri Van der Wat and Patricia B. C. Forbes
Department of Chemistry, University of Pretoria, Hatfield, South Africa

Published By: Environmental Science and Pollution Research

Issue: 26

Year of Publication: 2019

Link: https://link.springer.com/article/10.1007%2Fs11356-019-04587-3

Abstract: Lichens are useful biomonitors for atmospheric polycyclic aromatic hydrocarbons (PAHs). Different sample preparation techniques were explored in this regard, including ultrasound-assisted solvent extraction, microwave-assisted extraction, Soxhlet, and the quick, easy, cheap, effective, rugged, and safe (QuEChERS) technique. It was found that a QuEChERS technique using hexane:acetone (1:1, v/v), never reported before for application to lichens, provided the best recoveries of internal standards, the highest total peak area for all PAHs of interest, and %RSDs comparable with the other preparation techniques tested. The optimized sample preparation technique was found to be a comparatively fast method (45 min), with good recoveries (96%), using less solvents and minimal energy consumption. Strong matrix effects were found: both strong enhancement (for the lighter PAHs) and strong suppression (for the heavier PAHs). The use of matrix-matched standards is thus imperative for the accurate determination of PAH concentrations in the lichen samples.

Acknowledgment(s): Restek Corporation and Wirsam Scientific are
thanked for their support of this research.

Increase Sample Throughput with New 15-Minute, Low-Level PAH GC-MS Analysis

Published By: Restek Corporation

Year of Publication: 2018

Link: http://www.restek.com/Technical-Resources/Technical-Library/Environmental/env_EVSS2836-UNV


Polycyclic aromatic hydrocarbons (PAHs) are analyzed at low levels around the world in order to protect human and environmental health. The PAH GC-MS analysis shown here uses SIM mode and column and method parameters scaled down from a commonly used semivolatiles method. Good chromatographic results were achieved down to 0.05 ng on-column in a fast, 15-minute analysis time.

Attend Restek’s SS AOAC Luncheon Workshop

This year at SS AOAC, in addition to being a proud sponsor, Restek is offering a luncheon workshop on method development and improvement using our free and easy EZGC® online tools. If you are planning to attend SS AOAC, we invite you to join presenter Rebecca Stevens for what is sure to be a valuable and enjoyable experience.

In addition, Restek’s Julie Kowalski will be presenting a poster on PAH analysis using a modified QuEChERS extraction and no sample cleanup.

Visit www.restek.com/SSAOAC to read abstracts, easily contact the presenters, and access the SS AOAC website for additional event details.

Restek at SS AOAC

Restek Releases the First Standard to Contain all Major PAH Interferences

PAH_interf_stds_PRThe new PAH interferences standard from Restek is the first and only certified reference material formulated to contain all major PAH interferences for priority PAHs. Analysts can use this mixture to quickly confirm the presence of common interferences by retention time comparisons. Since the PAH components are present in different concentrations, isomers can easily be distinguished by the difference in their response factors. Several key PAHs of health concern–such as chrysene and benzo[b]fluoranthene–coelute with other PAHs on most GC columns, which biases results. To ensure accurate reporting, this standard can be paired with an Rxi®-PAH column and Restek’s EU 15+1 PAH standard to optimize method conditions and ensure separation of interferences and target PAHs. As this new PAH interferences standard meets strict ISO quality requirements, it is also suitable for quantitative work as a calibration or fortification standard.



PAH Interferences Standard 250–1,000 µg/mL, Toluene, 1 mL/ampul

Cat.# 32472

Compound CAS# Concentration (µg/mL)
Benzo[k]fluoranthene 207-08-9 1,000
Benzo[j]fluoranthene 205-82-3 750
Triphenylene 217-59-4 750
Benzo[e]pyrene 192-97-2 500
Perylene 198-55-0 250


New EU 15+1 PAH Standard Offers High Stability and Dilution Flexibility

EU15+1PAHstandards_CRMRestek is pleased to announce the release of a new EU 15+1 PAH reference standard for the analysis of PAHs in food and environmental samples. Formulated to contain the 16 major European Food Safety Authority (EFSA) PAH compounds, this new high concentration (100 μg/mL) blend can be diluted as needed to make economical fortification and calibration mixes. Our formulations chemists prepared this standard in toluene, as its lower volatility helps ensure longer shelf life, more accurate results, and suitability with both GC and LC methods. In addition, its broad solvent miscibility makes it compatible with acetonitrile, which is the QuEChERS solvent. In addition, being manufactured and QC-tested in Restek’s ISO-accredited labs means this standard will also help satisfy strict ISO requirements for the use of CRMs. This new standard is the latest addition to Restek’s expanding suite of products for PAH analysis. Restek also offers specialty GC and LC columns (Rxi®-PAH, Pinnacle® DB PAH, and Pinnacle® II PAH), certified reference standards, Q-sep® QuEChERS salts, Resprep® SPE cartridges, and other products for high-quality chromatographic separations of critical polycyclic aromatic hydrocarbons.


Analytical Method for Polycyclic Aromatic Hydrocarbons (PAHs) in Yerba Mate Tea Using Modified QuEChERS, Solid Phase Extraction and GC-TOFMS and GC-MS/MS

Author(s): Julie Kowalski, Amanda Rigdon, and Jack Cochran
Restek Corporation

Published By: Restek Corporation

Year of Publication: 2015

Link: http://www.restek.com/Technical-Resources/Technical-Library/Foods-Flavors-Fragrances/fff_FFAN2086-UNV

Abstract: This application note describes the development of an analytical method for PAHs in tea that allows analysts to more quickly and accurately characterize target PAHs. Sample preparation is based on a modified QuEChERS extraction and solid phase extraction sample cleanup. Both GC-TOFMS and GC-MS/MS techniques were used and analyses were optimized for resolution of isobaric compounds, as well as for maintaining a reasonable analysis time.

Restek’s New EFSA PAH4 Standard Offers Low-Volatility Accuracy and High-Concentration Versatility

Restek's EFSA PAH4 CRMThe formulations chemists at Restek have developed a new certified reference material (CRM) of four PAHs—benz[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, and chrysene—designed for greater convenience, longer shelf life, and increased long-term accuracy. Its high 1,000 µg/mL concentration gives analysts the freedom to dilute as needed for greater control and more economical custom mixes. The toluene solvent offers not only low volatility, but also high miscibility with QuEChERS solvents like acetonitrile. In addition, being manufactured and QC-tested in Restek’s ISO-accredited labs means this standard will also help satisfy strict ISO requirements for the use of CRMs.

Restek’s new PAH standard is ideal for pairing with the rugged and uniquely selective Rxi®-PAH column. This innovative GC column is able to easily separate European Food Safety Authority (EFSA) PAH4 compounds from common interferences like triphenylene; cyclopenta[cd]pyrene; and benzo [k], [ j], and [a] fluoranthenes. Restek also offers Q-sep® QuEChERS salts, Resprep® SPE cartridges, and more for unbeatable PAH analyses in food or environmental samples.


DO NOT PUBLISH — ISPAC 2013 to Feature Session Co-Chaired by Restek’s Jack Cochran

Restek is proud to be a sponsor of the 2013 International Symposium on Polycyclic Aromatic Compounds (ISPAC) being held from September 8–12 on the campus of Oregon State University in Corvallis, Oregon. According to ISPAC, this year’s event “will focus on the research of Polycyclic Aromatic Compounds (PACs) on multiple fronts of analytical measurements, toxicology, organic synthesis, human exposure and health effects, and environmental presences, sources, fate, and transport. It is a forum that brings together researchers worldwide to communicate, learn, and advance the field of PAC.”

Jack Cochran

Jack Cochran

We are looking forward to what promises to be an enlightening and informative week of discussion and collaboration with our colleagues from around the world. We especially invite you to sit in on the “GCxGC for PAC Analysis” session, which will be co-chaired by Jack Cochran, Restek’s Director of New Business & Technology, along with Allen Zhang of LECO Corporation. Jack will also present his work during the session in a talk titled “GCxGC-TOFMS and GC-MS/MS Using a Novel GC Stationary Phase for the Unbiased Determination of Important PAHs”.

For a full schedule of events and presentations, or more for information on ISPAC, visit www.ispac2013.com or e-mail Jack Cochran at jack.cochran@restek.com

New GC Column Separates all EFSA PAH4 Priority Compounds

PAHs in foodRestek has developed a GC column specifically for the analysis of polycyclic aromatic hydrocarbons (PAHs) in food safety and environmental samples. The new Rxi®-PAH column features a higher phenyl-content stationary phase that provides a unique selectivity to separate important PAHs that cannot be distinguished by mass spectrometry. Even difficult priority compounds, such as the European Food Safety Authority (EFSA) PAH4, are easily separated and accurately quantified, results that cannot be achieved on typical GC columns. The selectivity and efficiency of the Rxi®-PAH column make it ideal for EFSA PAH4 analysis; chrysene triphenylene separation and resolution of all benzofluoranthenes are easily achieved.  Excellent column efficiency means critical PAH separations can be maintained when the column is trimmed. In addition, the rugged, arylene-modified stationary phase is stable up to 360 °C, which ensures that relatively nonvolatile, higher molecular weight PAHs, such as dibenzo pyrenes, can be analyzed routinely without interference from column bleed.  Separation of benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[a]pyrene, and other PAH compounds make Rxi®-PAH columns ideal for EFSA PAH4 analysis, as well as other environmental and food safety testing. Visit www.restek.com/rxi-pah for product details.