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


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.

Quantitation of Mycotoxins in Four Food Matrices Comparing Stable Isotope Dilution Assay (SIDA) with Matrix-Matched Calibration Methods by LC–MS/MS

Author(s): Dan Li; Justin A. Steimling; Joseph D. Konschnik, Scott L. Grossman; Ty W. Kahler
Restek Corporation

Published By: Journal of AOAC International

Year of Publication: 2019


Abstract: Background: Mycotoxins are big concerns in food safety. Analytical methods are important for the evaluation of mycotoxins in different food commodities. Objective: In this study, stable isotope dilution assay (SIDA) was compared with a matrix-matched calibration method for the quantification of mycotoxins in four different commercially available commodities and two reference materials. Methods: All samples were extracted with water–acetonitrile (50+50, v/v), followed by filtration and LC–tandem MS analysis. Results: SIDA calibration accuracies ranged from 78.6 to 112% with relative SDs (RSDs) ≤16% across all four matrices. The majority of the recoveries across all matrices ranged from 70 to 120% with RSDs <11%. Of the four mycotoxins in the reference materials analyzed, only three had 13C-internal standard (IS), whereas the fourth was quantified using a closely eluting 13C-IS for a different mycotoxin. Mycotoxins paired with their corresponding 13C-IS had accuracies >90%, whereas accuracies for the mismatched mycotoxin/13C-IS were <14%. Conclusions: When 13C-IS are not available, matrix-matched calibration was also evaluated as an alternative to quantitating target mycotoxins. The use of 13C-IS is the best way to dynamically account for prevalent matrix effects, but matrix matching provides a viable alternative. Highlights: The study compared SIDA and matrix-matched calibration methods in terms of recovery, efficiency, advantages, and limitations for LC-MS based mycotoxin analysis

Evaluation of a Simple Method for Methylmalonic Acid Analysis in Human Plasma by LC-MS/MS

Author: Justin Steimling and Frances Carroll

Published By: Restek Corporation

Year of Publication: 2019



A new LC-MS/MS method for methylmalonic acid (MMA) analysis was developed that provides complete chromatographic resolution from isobaric succinic acid in plasma samples. Excellent chromatographic results were obtained from the direct injection of a protein crash sample supernatant onto a Force C18 column, providing a much simpler sample preparation compared to typical methods.

New CBGA Reference Standard for Your Cannabis Potency Testing Program

Restek’s ever-growing selection of cannabis reference standards has expanded again with a new cannabigerolic acid (CBGA) CRM. This certified reference material (CRM) is U.S. DEA exempt, so there’s no need to purchase costly neat materials, make your own standards, or deal with DEA forms and registrations. Verified in composition and stability, this CBGA standard is ideal for combining with other Restek cannabinoid CRMs for quantitative potency analysis using the Raptor ARC-18 LC column. And like all Restek certified reference materials (CRMs), it is manufactured and QC tested in ISO-accredited labs to satisfy your ISO requirements.

Your CBGA standard is in stock now at You can also find it, along with the rest of Restek’s cannabis analysis solutions, at

Resprep EPH Fractionation SPE Cartridges: Now Available in a 2 g Format

Resprep EPH fractionation SPE cartridges offer method-specific performance for extractable petroleum hydrocarbon (EPH) analysis of soil and water samples. These high-performing SPE cartridges completely separate aliphatic and aromatic compounds into distinct fractions, and they are guaranteed to produce background levels under the strict reporting limits of MA and NJ EPH methods. Our standard 5 g format cartridges are now joined by 2 g format cartridges made from the same high-quality silica. While the 5 g cartridges are recommended when higher loading capacity is required, the new 2 g cartridges are ideal for automated systems or when time-saving and solvent reduction are desired. As always, our rigorous QC testing and moisture-resistant packaging ensure storage stability and consistent lot-to-lot performance.
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Restek Honored by Leading Science Publication

Of the thousands of reviews on SelectScience, Restek had the highest average rating in 2018

Restek President Bryan Wolcott accepting the SelectScience Reviewers’ Choice Award for
Analytical Science Company of the Year.

The reviews are in and Restek is on top.

Leading independent science publisher SelectScience presented Restek with its Reviewers’ Choice Award for Analytical Science Company of the Year, in recognition of the high ratings and positive feedback it received from customers leaving laboratory product reviews on its influential website.

The award was presented to Restek President Bryan Wolcott by SelectScience Editor-in-Chief Kerry Parker.

“These awards are truly unique within the science industry—the only awards where scientists themselves decide who should win,” Parker said.

Winners and nominees of the annual Scientists’ Choice Awards were celebrated during a glitzy SelectScience party on March 21 at the Pittcon 2019 International Conference and Expo in Philadelphia.

“It’s an honor to be among the winners and nominees who are making waves in the fields of general lab, spectroscopy, and separations,” Wolcott said. “We work hard every day to create products that meet the high expectations of our customers. Thank you SelectScience and the scientific community for recognizing our efforts.”

Of the thousands of reviews by users on SelectScience, the award recognized Restek for having the highest average rating in 2018.

This is the second award Restek received this year. In January, Global distributor Avantor presented Restek with its Platinum Level Achievement Award for Operational Excellence to recognize Restek’s commitment to enrichment, cooperation, quality assurance, and shipping performance.