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From: Food Quality & Safety magazine, February/March 2011

Advances in LC/MS for Food Safety Testing

New liquid chromatography/mass spec technologies make a difference in the lab

by Andre Schreiber and Art Sims

The QTrap 5500 LC/MS/MS system is designed to excel at metabolite identification, detection and confirmation of low-level pesticides and protein-peptide quantitation for biomarker verification and validation.
The QTrap 5500 LC/MS/MS system is designed to excel at metabolite identification, detection and confirmation of low-level pesticides and protein-peptide quantitation for biomarker verification and validation.

The scope, relevance, and level of food safety regulation and testing have never been higher than in today’s global marketplace. President Barack Obama’s signing of the U.S. Food and Drug Administration (FDA) Food Safety Modernization Act (PL 111-353) in January signaled a renewed urgency and commitment to expanding the safety net of food testing and protection measures not only in the United States but around the world.

It’s no surprise. Each year, nearly 48 million people in the United States get sick from contaminated food; some 128,000 are hospitalized, and there are 3,000 foodborne illness-related deaths.1 As more of our food comes from farther afield, the opportunity for contamination, both manmade and naturally occurring, can only increase. In the United States alone, an estimated 15% of the food supply is imported, including 50% of fresh fruits, 20% of fresh vegetables, and 80% of seafood.2 The need for timely, accurate testing at every point along the farm-to-table pathway has never been more acute.

As a result, food suppliers, producers, manufacturers, and local, state, federal, and global regulatory agencies are all facing greater pressure than ever before to test more food products for more contaminants and quantify their presence at lower levels with greater accuracy—and in less time. Advances in screening technologies help to ensure that these critical lines of defense can meet the myriad of new testing requirements and, most importantly, protect the global food supply.

Advances in LC/MS

Food safety relies on a web of technologies to facilitate ongoing food supply monitoring. Mass spectrometry has a long and proven track record of enabling food testing labs to identify and quantify foreign substances in food. Recent advances in the integration of chromatographic separation techniques with tandem mass spectrometry bring a very high level of sensitivity and selectivity to food testing, particularly for the specific detection and identification of contaminants in the presence of other chemicals in a complex matrix.

In recent years, the utilization of liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) has grown rapidly and is now widely recognized as an ideal, highly specific, and extremely sensitive technique for testing food products with superior accuracy and higher throughput than other methods such as LC/ultraviolet (LC/UV), LC/fluorescence, or microbiological and enzyme-linked immunosorbent assay methods. The ability to monitor dozens, sometimes hundreds, of contaminants in a single run greatly improves throughput, and new levels of sensitivity allow more simplified sample preparation protocols. New levels of platform sensitivity allow detection of lower levels of contaminants with less sample preparation, and new workflows, such as multiple reaction monitoring (MRM3), provide unique specificity to help measure low level contaminants in complex matrices. These advanced LC/MS/MS platforms provide the capacity to screen for more analytes at lower levels, with greater accuracy, and in less time.

Recently developed workflows provide high sensitivity quantitative information, as well as supporting data to confirm the identification of contaminants found. The workflow uses the high sensitivity MRM functionality to provide sensitive and accurate quantitation while simultaneously acquiring full scan MS/MS spectra that can be matched to spectral libraries to provide high-confidence identification. The full scan MS/MS spectra functionality is also applied to screening for unexpected or unknown contaminants.

Simplified Sample Preparation

The drive toward decreasing time to results places significant demands on food testing laboratories to do more, faster. Preparative steps associated with sample testing are often the most time consuming and can be prone to error or the introduction of unrelated contaminants. As a result, for many technologies, sample preparation has been a rate-limiting step to achieving higher throughput in screening applications.

New levels of platform sensitivity allow detection of lower levels of contaminants with less sample preparation, and new workflows, such as multiple reaction monitoring (MRM3), provide unique specificity to help measure low level contaminants in complex matrices.

The sensitivity and specificity of LC/MS/MS can help to minimize extensive cleanup or pre-concentration steps. In some cases, a sample extract can be directly injected, enabling a “dilute and shoot” workflow.3 Also, sample derivatization is rarely required, unlike GC/MS, for which a time-consuming derivatization step is often necessary to improve ionization and/or volatility.

Great progress has been made toward applying more universal sample preparation to LC/MS/MS analysis. The QuEChERS (quick, easy, cheap, effective, and safe) extraction technique for extracting pesticides from food and feeds takes advantage of the sensitivity and specificity of LC/MS/MS for multi-residue pesticide screening and has the potential to be applied to a broader range of contaminants.4

Better Compound Coverage

Globalization of the food supply has necessitated screening for a wider range of potentially harmful substances. Raw materials and finished products alike are subject to contamination or adulterants that can originate almost anywhere along the farm-to-table pathway. Chemical testing has to cover a broader range of contaminants, and biological testing must identify bacteria and viruses that may be present in the food, as well as determine the exact serotype of each microbe, to locate the origin of the contamination.

Mycotoxins, for example, are low-molecular weight, chemically diverse toxins that are produced naturally by molds commonly found in grains and fruit and have been linked to a wide range of negative health effects. Aflatoxin, for example, is the most potent natural carcinogen known to man, and ochratoxin has been shown to damage the liver, kidney, and immune system.

LC/MS/MS is a powerful tool for the analysis of mycotoxins, because the workflow can screen for, quantitate, and identify several classes of mycotoxins in a single run, allowing laboratories to confirm the presence and structure of multiple mycotoxins and metabolites simultaneously in a significantly reduced amount of time. What used to require multiple analyses on multiple MS platforms now involves only a single LC/MS/MS run on a single system. This is not possible using technologies such as LC/UV, one of the most widely used screening techniques over the last 10 years.

In a recent multi-residue mycotoxin analysis and field study of wheat, barley, oats, rye, and maize grain, researchers at the University of Guelph, Laboratory Services Division, in Ontario, Canada were able to demonstrate a durable method for the simultaneous analysis of 22 mycotoxins in a single LC/MS/MS run using one common extraction technique rather than employing several different extractions and instruments.5 Further, the researchers found that “such a method offers a distinct advantage over other mycotoxin methods not only because it is cheaper and more efficient, but because it considers the toxicological relevance of the target mycotoxins.” Data generated from this study will also be used to advance the understanding of a wide range of mycotoxins, including cyclopiazonic acid, in cereals and grains and other matrices.

AB Sciex QTrap technology combines the highest sensitivity multiple reaction monitoring quantitation with high sensitivity full-scan MS/MS spectra in a single run.
AB Sciex QTrap technology combines the highest sensitivity multiple reaction monitoring quantitation with high sensitivity full-scan MS/MS spectra in a single run.

The FDA, which manages one of the world’s most sophisticated and far-reaching food supply monitoring programs, samples individual lots of domestically produced and imported foods and analyzes them for pesticide residues. LC/MS/MS gives the agency a technology that integrates quantitative and qualitative analysis on the same platform and performs automated identification of a wide range of contaminants simultaneously.6

Improved Technology

Developments in LC/MS/MS have been central to recent technology advances in food safety testing. LC/MS/MS enables laboratories not only to test for the presence of hard-to-detect toxins, but also to identify metabolites that may be formed after contamination and address the continually lowering detection limits required by global regulations. The technology is also widely applied in screening for other food contaminants such as pesticides, veterinary drug residues, marine biotoxins, and packaging materials.

Recent advances in mass spectrometry systems have significantly advanced both quantitative and qualitative analysis. The ability to quantify contaminants and obtain identification confirmation in a single run enables new levels of productivity. New levels of sensitivity and specificity allow lower levels of contaminants to be monitored and quantified with simplified sample preparation. Also, advances in high-resolution LC/MS/MS systems, complemented by new software tools, provide unique capabilities to screen for unexpected contaminants.

Outbreak investigations and routine screening play a central role in combating foodborne illness. Together, these efforts help identify new contaminants, new food vehicles, and unsuspected holes in the food safety net. They also help deepen the scientific understanding of how contamination occurs at specific points in the food supply chain, identify any likelihood that it may occur again, and plan ways to reduce or prevent it.

The number of components that must be monitored on the farm-to-table pathway will continue to increase, while allowable levels of contamination will continue to decrease. Food safety technologies will have to continue to advance their capacity to screen for more contaminants in less time and in easy-to-use formats. There will also be more requirements for general unknown screening or for identifying and measuring unexpected contaminants. This will require assays with high throughput, high sensitivity, and advanced tools to identify unknown or unexpected contaminants.

LC/MS/MS plays an important role in detecting threats to the food supply and in deepening our understanding of potentially harmful contaminants. As new technology advances are made, this versatile platform will continue play a greater role in protecting the global food supply.

Schreiber and Sims are technical marketing managers for food safety and environmental testing at AB Sciex. Reach Sims at (508) 383-7824.

References

  1. United States Centers for Disease Control and Prevention. CDC estimates of foodborne illness in the United States: 2011 estimates. Available at: www.cdc.gov/foodborneburden/2011-foodborne-estimates.html. Accessed January 30, 2011.
  2. United States Food and Drug Administration. Food Safety Modernization Act: putting the focus on prevention. Available at: www.foodsafety.gov/news/fsma.html. Accessed January 30, 2011.
  3. Von Czapiewski K, Voller A, Schlutt B, Schreiber A. Tech note: simultaneous analysis of 14 mycotoxins and 163 pesticides in crude extracts of grain by LC-MS/MS. AB Sciex.
  4. Anastassiades M, Lehotay SJ, Stajnbaher D, et al. Fast and easy multiresidue method employing acetonitrile extraction/partitioning and “dispersive solid-phase extraction” for the determination of pesticide residues in produce. J AOAC Int. 2003;86(2):412-431.
  5. Martos PA, Thompson W, Diaz GJ. Multiresidue mycotoxin analysis in wheat, barley, oats, rye and maize grain by high-performance liquid chromatography-tandem mass spectrometry. World Mycotoxin J. 2010;3(3):205-223. Available at: http://wageningenacademic.metapress.com/content/nlv525p0123q1557. Accessed January 30, 2011.
  6. AB SCIEX. Press Release: U.S. Food and Drug Administration selects AB SCIEX to provide mass spectrometry systems for food contaminant testing. October 20, 2010. Available at: www.absciex.com/Company/News-Room/US-Food-and-Drug-Administration-Selects-AB-SCIEX-to-Provide-Mass-Spectrometry-Systems-for-Food-Contaminant-Testing. Accessed January 30, 2011.

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