Mitigating Matrix Effects: Examination of Dilution, QuEChERS, and Calibration Strategies for LC-MS/MS Analysis of Pesticide Residues in Diverse Food Types

Author(s): Julie Kowalski, Sharon Lupo, and Jack Cochran
Restek Corporation

Published By: Restek Corporation

Year of Publication: 2013


Abstract: Liquid chromatography tandem mass spectrometry (LC-MS/MS) is popular for monitoring pesticide residues in food. The increased selectivity and sensitivity of LC-MS/MS have impacted how multiresidue methods are performed, sometimes decreasing the need for rigorous sample preparation. However, this approach suffers from matrix effects causing poor data quality and difficult quantification. Matrix effects can be mitigated by sample preparation that reduces the concentration of coextracted matrix material or by experimental strategies like matrix-matched calibration that compensate for matrix effects. We considered these two aspects of multiresidue methods, sample preparation and calibration strategies, in order to determine recommendations that balanced data quality as well as time and financial investments.

We performed matrix effects studies investigating two approaches for reducing matrix interferences, QuEChERS sample preparation and dilution, in combination with the compensation strategy of matrix-matched calibration compared to solvent calibration. There are compromises with each method regarding time and financial resources. A variety of food types were tested including high water (celery), high pigment (kale), high fat (avocado), citrus (lime), and dry (brown rice flour) foods, with subsequent pesticide residue analysis by LC-MS/MS. Samples were fortified at high and low ppb levels with over 100 pesticides representing multiple classes.

We determined that with the easiest commodities, the dilution method and solvent-only calibration gave acceptable recovery values. However, for other commodities either a matrix-matched calibration curve and/or cleanup were needed to obtain good recovery values. The high carbohydrate and citrus commodities proved to be too difficult with the specific methods we tested here. In almost every case, use of matrix-matched calibration provided improvement.


Ghost Peaks in Gas Chromatography Part 2: The Injection Port

Author(s): Jaap de Zeeuw
Restek Corporation

Published By: Separation Science

Issue: vol. 5, issue 5

Year of Publication: 2013


For the full print issue, visit

Abstract: In Part I, we discussed possible sources for ghost peaks related to the carrier gas and the gas lines. Here we move into the injection port itself as this is a big source for “trouble”. The injection of the sample is responsible for > 80% of the “troubles” that are experienced in gas chromatography. In the process of rapid evaporation of the sample, several things can go wrong.

Chromatography Mastermind Campaign Earns American Inhouse Design Award

Are You A Chromatography Mastermind?Graphic Design USA has presented Restek Corporation with a 2013 American Inhouse Design Award for its Chromatography Mastermind tradeshow materials. Of the 4,000+ entries submitted each year, only the top 15% gain acknowledgment through this prestigious competition. The GD USA contest “is the original and the biggest showcase for outstanding work by inhouse designers. For many years, it has provided an opportunity for inhouse designers to be recognized for their talent, for the challenges they face, and for their contributions to their businesses and institutions.” Restek is proud to accept this honor and would especially like to applaud graphic designer Barb Roan for her exceptional efforts on this project.

This multi-component Chromatography Mastermind campaign was initially created to publicize Restek’s presence at Pittcon 2013. Specifically, its goal was increasing awareness of the Chromatography Mastermind quiz, which was assembled by technical representatives across the company as a way for customers to test themselves while having fun and learning more about the various presentations being offered at the show. The app, mailer, e-mail, T-shirt, website advertisements, stickers, signage, app, and other pieces were so well received by attendees that the iPad app quiz will now be making an appearance at several other events throughout Restek’s 2013 conference schedule.

If you are a chromatographer looking to test your knowledge with some separation science brain teasers, visit to see where this exclusive app will be challenging analysts next. Restek’s technical experts will also be on-hand to assist you with your chromatography struggles—and of course, Restek products and support are always available at

Inaugural Governor’s ImPAct Award Celebrates Restek for its Export Activities

2013 Governor's ImPAct Awards WinnerOn May 23, 2013, companies from around the state of Pennsylvania converged at the Hershey Lodge for the first annual Governor’s ImPAct Awards. This prestigious event was conceived by Governor Tom Corbett, the PA Department of Community and Economic Development, and the Team PA Foundation to pay tribute to businesses that are creating jobs and actively investing in Pennsylvania. To be eligible, companies first had to be nominated by their representative to the Partnerships for Regional Economic Performance (PREP) program. Then, the merits of each nominee were scored by an independent panel of judges to determine the final winners in each PREP region.

Three representatives from Bellefonte-based Restek Corporation—Shaun Smith, Karen Kishbach, and Nicole Simpson—accepted the Export Impact award on behalf of the employee-owners of Restek. This award comes soon after Restek announced the opening of a new subsidiary in the People’s Republic of China—joining offices in the U.S., France, Germany, UK, and Japan in addition to a distributor network that covers over 100 countries across six continents. As a company that started so humbly in a single room of a business incubator just over 25 years ago, Restek is honored to be recognized for its expansion into a global provider of cutting-edge chromatography products and world-class Plus 1 service.

To learn more about Restek products, services, and career opportunities, please visit

Shaun Smith, Karen Kishbach, and Nicole Simpson accept the Governor's ImPAct Award from the 2013 award judges on behalf of Restek. (Photo courtesy of CPBJ/Amy Spangler.)

Shaun Smith, Karen Kishbach, and Nicole Simpson accept the Governor’s ImPAct Award from the 2013 award judges on behalf of Restek. (Photo courtesy of CPBJ/Amy Spangler.)