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Explore This IssueJune/July 2012
When a crisis emerges in our food supply—whether it is a foodborne illness outbreak, a recall due to the presence of an allergen, or identification of unwanted contaminants in imports/exports—consumers become concerned, and food producers and regulators are forced to respond quickly.
A typical response to a food safety crisis entails an uptick in product safety testing. Regulators, food producers, and technology companies all bear the responsibility of ensuring that the food safety test methods developed to identify potential contaminants are reliable, accurate, and robust.
The recent discovery of the fungicide carbendazim in orange juice samples imported to the United States from Brazil is one example of how a food safety concern made the development of new food testing methods necessary.
Carbendazim is a fungicide used to treat citrus trees in Brazil against diseases such as black spot. While this compound is approved for use in some countries, it is not approved by the U.S. Environmental Protection Agency for use on oranges. Given that the United States reportedly imports 15% of its orange juice supply, the majority of which comes from Brazil, the detection of this substance brought about an investigation in early 2012, culminating in a notice of action by the FDA for increased testing of orange juice shipments to the U.S. and throughout the world.
With the call to action for increased orange juice testing, food testing labs were tasked with quickly developing a method of analysis. Although this task seems straightforward, the method requirements are quite stringent.
The method must be accurate: How true is the value of contaminant identified in the sample? The method must be precise: Will you get the same results for multiple analyses of the same sample? The method must be selective and specific: Is what you are identifying as carbendazim actually carbendazim? The method must be robust: Will you get the same results hour after hour, day after day, regardless of small changes in external conditions? The method must be adequately sensitive: Are you able to detect the compound at concentrations relevant to the demands of global importing and exporting? All of these components funnel into one main characteristic—reliability: Are you sure your positive samples are actually positive and your negative samples are actually negative?
All of these requirements must be achieved within a very short turnaround time, an additional element of strain. For these reasons, scientists often employ advanced food testing technologies to get the job done. In the case of the analysis of carbendazim in orange juice, LC-MS/MS was the “go-to” method.
The Science of Crisis Response
When a food testing lab responds to a call to action, the method development process begins. Food safety labs place intense focus on the key method elements of accuracy, precision, specificity and selectivity, robustness, sensitivity, and, of course, reliability.
Method accuracy. Accuracy, measured against the result determined for an accepted reference material or standard, is sometimes difficult to address in food safety testing method development. Frequently, control or reference samples of the same type of interest—orange juice with a known amount of carbendazim, for example—are difficult or impossible to obtain. As a result, labs often use the standard additions approach (fortification of a negative control sample with the compounds of interest) to determine method accuracy.
In method development, accuracy measurements are typically the fundamental elements used to address method performance: Is the method efficiently extracting the compound of interest from the sample? Are additional sample cleanup steps required? Are the sample cleanup steps efficient? Are there interferences present from the matrix? It is not uncommon for a lab to go through multiple iterative changes in the sample preparation procedure before settling on a method with acceptable performance.
To demonstrate that the method will be reliable at various contaminant concentrations, accuracy must typically be assessed at different concentration levels—whether carbendazim is present at 10 ppb, 100 ppb, or even 1000 ppb.
Method precision. Method precision is typically evaluated simultaneously with method accuracy, where the precision can most simply be determined through repeated measurements of standard additions control samples. Most laboratories prefer to assess precision by taking at least three measurements at each concentration level, although more measurements are ideal.
Method selectivity and specificity. Accuracy and precision are certainly key elements to method development and performance evaluation, but is the method selective for the compound of interest? Selectivity and specificity are key method criteria that ensure that the observed measurement is due to the presence of the compound of interest and that the compound of interest can be identified reliably even in the presence of many other components in the sample.
The power of LC/MS/MS technology enables method development scientists to assess selectivity and specificity quickly, accurately, and reliably. LC/MS/MS incorporates three key selection criteria, HPLC retention time, the distinct molecular mass of the compound, and the distinct mass of one or more fragments of the compound (characterized breakdown products based on the chemistry of the compound), to confirm that the analysis is selective and specific for the compound of interest.
Additionally, through the use of linear ion trapping technology, compound fragmentation is taken a step further, and a fourth dimension of selectivity is incorporated. With linear ion trapping LC/MS/MS technology, a complete product fragment scan can be evaluated, including the masses of all breakdown products of the compound and the relative abundance of each. These four points of selectivity make LC/MS/MS a powerful tool for quick and reliable method development.
Method robustness. Regulators and food producers often survey many samples to evaluate the breadth of a problem or crisis. This is why method robustness is also critical in responding to a food crisis. Perhaps multiple chemists are preparing solutions and samples, multiple HPLC columns or instruments are used, and instruments are required to run repeated injections for many hours at a time. It is important that these elements do not affect method performance or the reliability of results.
Well-rounded robustness studies are often quite difficult to complete for a new method created in response to a food crisis, primarily due to the time constraints labs face in trying to get the method up and running quickly. As a result, labs often choose to keep their methods as simple as possible, using the most sensitive and reliable instrumentation possible. Fewer procedure variables can be a key factor in ensuring method robustness.
Method sensitivity. All of these elements of the method are important, but if the method is not able to detect the compound of interest at concentrations relevant to what is regulated in the global food import/export markets, then the method has no value. As a result, method sensitivity is a critical consideration in the method development process. Technology plays a key role in enabling labs to achieve the sensitivity required for an analysis.
For the analysis of carbendazim in orange juice samples, for example, sensitivity was essential. Because the compound is not approved by the U.S. government for use on oranges, it is not allowed at any level in oranges or orange products, and highly sensitive methods are key to accurately assessing violations.
Method reliability. The biggest pressure in food safety testing is merging all of the elements listed above to produce a method that is reliable. A wrong result can be incredibly expensive for food producers and government agencies, devastating to a food brand, and most importantly, a risk to consumer health.
The food testing lab’s responsibility to produce reliable results is greater than ever. By evaluating all aforementioned elements during method development, while incorporating innovations in technology for food safety testing, testing labs are, more than ever, playing a key role in keeping our food safe.
Companies that provide the food testing industry with analytical instruments and systems are also finding new ways to quickly respond to crises with new tools. One example is the collaboration that AB SCIEX recently formed with Phenomenex. The two companies are working together and with leading industry experts to respond to new food crises rapidly, providing labs with turnkey, verified LC/MS/MS methods that save time and money.
There are many key elements in developing good food testing methods. While only six of those elements are presented here, labs continuously evolve the science of food testing and their approaches to developing robust, accurate, and reliable food testing methods.
In our ever-growing global food market, food producers and food consumers ultimately have the same goal—to ensure safe, high quality goods. As much as we’d like to prevent them, food safety crises like the detection of carbendazim in orange juice are likely to occur in the future. Through innovations in technology and expansion of expertise, responses to these crises will continue to improve and will reduce—and ultimately eliminate—the global impact of food scares.
Lauryn Bailey, PhD, is global marketing manager of food and environmental markets for AB SCIEX. Reach her at email@example.com.
- Rapid quantitation and identification of carbendazim in orange juice using LC-MS/MS. Andre Schreiber and Lauryn Bailey, AB SCIEX technical notification. Available at: www.absciex.com/Documents/Downloads/Literature/Carbendazim-orange-juice_AB-SCIEX_ 4980212-02.pdf.
- Method validation and quality control procedures for pesticide residues analysis in food and feed, Document No. SANCO/10684/2009. Available at: http://ec.europa.eu/food/plant/protection/resources/qualcontrol_en.pdf.
- Guidelines for validation of analytical methods for non-agricultural pesticide active ingredients and products. Biocides and Pesticides Unit, U.K. Available at: www.hse.gov.uk/biocides/copr/pdfs/validation.pdf.
- Guidance for industry: Analytical procedures and methods validation. Chemistry, manufacturing, and controls documentation. U.S. Department of Health and Human Services, FDA. Available at: www.labcompliance.de/documents/FDA/FDA-Others/Laboratory/f-505-method-validation-draft.pdf.