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


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.

Residual Pesticides Analysis of Botanical Ingredients Using Gas Chromatography Triple Quadrupole Mass Spectrometry

Author(s): Riki Kitano1, Tairo Ogura1, Nicole Lock1, Robert Clifford1, Julie Kowalski2, Jack Cochran2, Dan Li2
1. Shimadzu Scientific Instruments, Inc. 2. Restek Corporation

Published By: Restek Corporation

Year of Publication: 2019


Abstract: Dietary supplements, which are consumed worldwide, are made from various botanical ingredients. To be safe from pesticides exposure, residual pesticides must be monitored by chromatographic instrumentation. Issues arise, however, due to the fact these botanical samples are dried and cause large interferences in the chromatography. This study shows that the modified QuEChERS method combined with GC-MS/MS achieves consistent pesticides monitoring in botanical ingredients.

Acknowledgment(s): Originally published by Shimadzu Corporation in collaboration with Restek Corporation.

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.

7.5-Min Screening Analysis of Multiresidue Pesticides in Brown Rice Flour

Published By: Restek Corporation

Year of Publication: 2018


Abstract: Multiresidue pesticides analysis presents many challenges, from extensive lists of chemically diverse analytes to the negative effects of complex matrix components. The optimized chromatographic method described here allows the analysis of hundreds of compounds in as little as 7.5 minutes with a total cycle time under 10 minutes, ensuring fast, accurate sample screening and increased lab productivity.

Extraction | QuEChERS

Authors: Alexandria M. Pavkovich, David S. Bell

Restek Corporation

Published By: ScienceDirect

Year of Publication:  June 2018


Abstract: QuEChERS has become a widely accepted and highly adaptable method for pesticide residue analysis. The analytical scope and applicability of QuEChERS are expanding at a rapid pace. Numerous research groups work with QuEChERS for analysis of pesticides, veterinary drugs, mycotoxins, environmental and natural contaminants, drugs of abuse, and a number of other areas of interest.

The term QuEChERS is an acronym for Quick, Easy, Cheap, Effective, Rugged, and Safe. QuEChERS is a quick and relatively easy extraction method that uses low solvent volumes and a user-friendly collection vessel while providing acceptable and reproducible analyte recovery for a wide range of pesticides and target analytes. QuEChERS allows for the extraction of homogenized matrices by using salt formulations to drive the separation of the organic extraction solvent and water.

Q-sep Extraction Salts Make QuEChERS Even Easier

For years, the QuEChERS approach has made sample preparation faster and easier than traditional methods. Now, the new Q-sep extraction salts from Restek make an easy technique even simpler. Restek’s new, improved design provides the salts in a more granular form, so they flow freely and are easier to pour than powders. The convenient slim packets are easy to open and fit perfectly into extraction tubes, ensuring complete transfer without any spills. These new extraction salts offer the same technical performance you’ve come to expect from the Q-sep line of QuEChERS products, just redesigned for your convenience. Keep your workflow running smoothly with new Q-sep extraction salts from Restek!

Restek to Offer May 3 Twitter Q&A Session on QuEChERS

#AskRestekOn Tuesday, May 3, Restek will host the next installment of the popular #AskRestek question-and-answer (Q&A) series on Twitter. This free, hour-long chat forum with Restek chromatography experts will start at 3:00 p.m. Eastern Time (12:00 noon Pacific Time) and will focus on QuEChERS sample preparation. Whether Restek customers or not, analysts are encouraged to follow the chat and join in with their own questions.

Panelists will include:

Mike Chang (@MC_Restek), Restek’s Product Marketing Manager (PMM) for Sample Preparation

Jonathan “Munch” Keim (@MunchAtRestek), Restek’s Education Coordinator as well as former Technical Service Manager and Sample Preparation PMM..

To stay informed leading up to the chat, follow @Restek, @MC_Restek, and @MunchAtRestek on Twitter.

At 3:00 p.m. EST (12:00 noon PST), on Tuesday, May 3, follow along by simply visiting and clicking All Tweets (app) or Live (browser). Periodically refresh your browser or Twitter feed to catch the latest posts.

People interested in receiving a reminder to join the chat can email us. Restek will send a reminder on the day of the event to those who sign up.

To join in the conversation, simply tweet a question or comment on Twitter and be sure to include the #AskRestek hashtag in your post.

For additional help using Twitter, you can also go to

#AskRestek is your direct line to Restek’s chromatography experts on Twitter. Follow Restek on Twitter now for this event and more valuable chromatography information:

Attend Restek’s Vendor Seminar on GC-MS/MS Performance at RAFA 2015

In addition to exhibiting, Restek will hold a vendor seminar at the 7th International Symposium on Recent Advances in Food Analysis (RAFA). Presented by Restek’s own Julie Kowalski on November 5 at 1:30 p.m., this valuable seminar will explore prolonging GC-MS/MS performance by means of Shoot-and-Dilute injection versus analyte protectants. Prizes will also be given away to select attendees.

RAFA 2015 takes place on November 3–6, 2015 at the Clarion Congress Hotel Prague, Czech Republic. This biennial symposium summarizes the latest strategies and identifies current issues surrounding food quality and safety control analysis and bioanalysis. While at RAFA, be sure to also stop by Booth# 46 for a visit and to discuss our latest innovations in food science.

Visit today to register for the symposium and to sign up for Restek’s vendor seminar.

Prolonging GC-MS/MS Performance: Shoot-and-Dilute Injection versus Analyte Protectants

Thursday, November 5, 1:30 p.m.
Julie Kowalski and Jack Cochran
Restek Corporation

In gas chromatography–mass spectrometry (GC-MS), most problems occur on the front end, at the GC inlet, where compounds can degrade during hot splitless injection, active compounds can be irreversibly adsorbed to inlet liner surfaces, and nonvolatile material from dirty samples can compromise the transfer of less volatile compounds of interest from the inlet to the GC column. These issues are magnified due to the very slow inlet flow during splitless injection, which is typically less than 2 mL/min.

Two strategies to mitigate these issues will be demonstrated in this seminar. One approach is to use split injection, what we call, and “Shoot-and-Dilute.” With newer, more sensitive GC-MS/MS systems, LOD and LOQ requirements are often achievable using split injections at ratios of 10:1 or greater. Increased flow through the inlet during split injection minimizes residence time inside the inlet liner, which decreases compound degradation and adsorption, and maintains acceptable data quality longer. In addition, GC oven start temperature can be higher, thus reducing overall run time as well as the time needed to re-equilibrate the GC oven prior to the next analysis. Another benefit of split injection is improved peak shape for early eluting pesticides when injecting acetonitrile-based QuEChERS extracts.

The second strategy to overcome GC inlet problems is to use “analyte protectants,” which are essentially volatile and chromatograph-able masking agents such as sugars, diols, etc., that are co-injected with each sample and standard to temporarily occupy active sites in the GC inlet liner and column. These analyte protectants have low m/z ions and the mass spectrometer can essentially overlook them in favor of target compounds.

Both strategies were tested with multiclass pesticides and compared against a typical splitless injection method without use of analyte protectants for QuEChERS samples. For Shoot-and-Dilute, viability of split injection based on detectability of a wide range of analytes was determined. Optimized split injection, inlet, and initial GC oven temperatures were determined. Benefits of analyte protectants were evaluated by peak shapes and responses of both well-behaved and problem pesticides. The goal of both Shoot-and-Dilute and analyte protectants approaches is to improve initial and long-term chromatographic performance.

QuEChERS, GC Smoke Out Tobacco Pesticides

Author(s): Michelle Misselwitz, Jack Cochran, Julie Kowalski
Restek Corporation

Published By: Chromatography Techniques

Year of Publication: 2014


Abstract: Pesticides are used heavily on tobacco in order to increase crop production value; however, limited regulation creates the potential for high levels of pesticide residues to remain on finished tobacco products. Analysis of pesticides on tobacco is extremely challenging due the natural complexity of this botanical matrix. The work detailed here used the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) approach for extraction and GCxGC-TOFMS for analysis. In addition, the experimental design compared dispersive solid phase extraction (dSPE) and cartridge solid phase extraction (cSPE) cleanup approaches. The wide range of pesticides chosen for this study covered many of the 37 pesticides that have been approved by the U.S. EPA for use on tobacco. The combination of QuEChERS, GCxGC-TOFMS, and dispersive solid phase extraction cleanup allowed easy and accurate analysis and separation of target pesticide residues from the tobacco matrix.

QuEChERS: The Concept

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

Published By: Separation Science

Issue: vol. 5, issue 8

Year of Publication: 2013

Link: For the full print issue, visit

Abstract: The original QuEChERS sample preparation methods were designed for pesticide residue analysis of high water-content foods, specifically fruits and vegetables. QuEChERS methods provide “just enough” sample preparation because highly selective and sensitive modern instrumentation does not require extremely clean samples. In the first two installments of this series (#1 and #2), official methods were reviewed, as well as considerations for method development. Adjustments to the original methods for some difficult commodities and pesticides were reviewed as well. This article will focus on QuEChERS metamorphosis into a concept. “QuEChERS” will be used as a broad term in this article to describe not only modified QuEChERS methods but also methods based on QuEChERS principles. The success of QuEChERS relates back to the attributes set forth by the originators; Quick, Easy, Cheap, Effective, Rugged and Safe. In addition to these benefits, great flexibility and quick method development have encouraged the expansion of QuEChERS from specific methods to generic techniques, and now to a sample preparation concept.