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Pesticide Residue Quantitation: Pushing the Limits of Detection using LC-MS/MS

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Given the widespread application of pesticides for agriculture, their appropriate use is of significant importance to the integrity of the food chain and consumer safety. Although pesticides prevent food from being infected or contaminated by bugs/insects, unauthorized overuse can present serious health risks to consumers. Therefore, it is extremely important to ensure that the concentration of pesticides in food and food products are within a safe range. While this presents a difficult analytical challenge to food safety labs, improvements in quantitation enable successful detection and analysis of pesticides following regulated maximum residue limits (MRL) in food samples.

To gain an in-depth understanding of pesticide residue detection in food, and how improved quantitation technology is helping to overcome analytical challenges, we talked with Dr. Debadeep Bhattacharyya (DB), Sr. Manager of Product Marketing at Thermo Fisher Scientific Inc.

KS Given the potential health risks from high pesticide residue concentrations in food, how much of a problem is residue analysis and how do food safety labs currently accomplish this?

DB Pesticide use is strictly regulated. However, inappropriate applications of pesticides on crops can be a serious cause for concern. With hundreds upon hundreds of chemically diverse pesticides available, food safety labs need to have extremely sensitive analytical methods not only to detect each type of pesticide but also to analyze multiple pesticides within a single sample. This variation can create an analytical challenge in that approaches need to be robust and sensitive enough to detect very low levels of pesticides and specific enough to identify a diverse range of compounds. Currently, food safety labs primarily use a combination of gas chromatography (GC) and/or liquid chromatography (LC) coupled with mass spectrometry (MS) to achieve this.

KS What types of obstacles do labs face using current methods and what can be done to overcome these?

DB While GC-MS and LC-MS are useful tools for pesticide residue analysis, food safety labs do encounter challenges with low concentration detection, as current EU regulations now specify the most stringent maximum residue level (MRL) guidelines to date. To overcome this obstacle, labs are moving to liquid chromatography (LC)-tandem mass spectrometry (MS/MS) using triple quadrupole mass spectrometers to gain the additional sensitivity needed to reach these extremely low level requirements.

KS LC-MS/MS can be used for multi-residue analysis, how does this work with the specificity needed to comply with regulations and low maximum residue limits?

DB LC-MS/MS analysis is sensitive enough to detect residues at low concentration levels, and is also robust enough to do this without compromising specificity and accuracy of readings. The ability to detect multiple residues within a single sample, and having the confidence that all residues have been detected and identified is paramount with LC-MS/MS. Improvements in the triple quadrupole technology, specifically segmented quadrupoles, faster rod drivers and more powerful electron multipliers, and in detection capabilities allow these instruments to push the limits of detection even further.

KS What kind of role does sample preparation play in analysis given that there are diverse sample matrices, some of which can be more challenging than others?

DB Sample preparation is a critical step in pesticide residue analysis. Various types of food and food products require a thorough analysis, thereby posing challenges to scientists when preparing the sample and ensuring sufficient analyte extraction for LC-MS/MS. If done incorrectly, analyte can be lost through hydrolysis, oxidation, degradation, and other interactions before they even reach an instrument. Homogenization and QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) methods simplify sample preparation and extraction allowing retention of the highest yield possible for analyte detection using LC-MS/MS. Also, given the perishable nature of many samples, speed and quality in preparation and analysis is of utmost importance. LC-MS/MS is beneficial to working with complex sample matrices by providing fast and robust analysis while preserving high quality results.

KS With food standards growing increasingly stringent, how can laboratories ensure they consistently meet the requirements of regulators?

DB Advances in LC-MS/MS workflows allow scientists to overcome the challenges associated with meeting low MRL’s today and tomorrow through more sensitive, selective and accurate reads across a diverse range of compounds. These improvements enable the creation of reproducible and reliable analyses every time, providing confidence in quantitation, output and results so food safety labs know they are casting a wide net and gathering all the information well into the future.

Dr Debadeep Bhattacharyya was talking to Dr Karen Steward, Science Writer for Technology Networks.