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You are what you eat. Ensuring safety and integrity grows ever more complex.
In 2013, two world-class sprinters—American Tyson Gay and Jamaican Asafa Powell—tested positive for oxilofrine, a banned stimulant. Beyond athletic bans, this stimulant is not approved as a dietary supplement in the United States, but when a team of researchers used mass spectrometry to test 27 supplements sold in the U.S., they found oxilofrine in 14 of them.1 The scientists reported: “The drug oxilofrine was found in pharmacological and greater dosages in supplements labeled as containing methylsynephrine.”
Robert “Chip” Cody, product manager of JEOL (Peabody, Mass.), says, “Mass spectrometry can be used to characterize the nutritional composition of foods, identifying substances such as vitamins, carbohydrates and lipids.” As the performance-enhancing example shows, the applications go beyond nutrients. “Agnes Rimando at the USDA Agricultural Research Service used mass spectrometry to show that blueberries contain pterostilbene, a powerful antioxidant,” Cody says. “Khalid El Sayed at the University of Louisiana at Monroe is using mass spectrometry and other methods to characterize oleocanthal, a candidate anticancer compound, in freshly pressed olive oil.”
As explained by Paul B. Young, senior director, food and environmental business, at Waters Corporation (Milford, Mass.), “MS began to penetrate food testing largely to address food safety.” He adds, “This covers a broad range of hazards, but includes testing for things like pesticides, veterinary drug residues and other types of contaminants that may be present at low levels.” Cody notes that JEOL’s Direct Analysis in Real Time (DART) ion source, and other forms of MS, were “used to detect melamine in pet food and powdered milk.” This additive has caused cancer and other health problems in animal studies, according to the World Health Organization.
Analyzing this range of applications requires a variety of technological approaches. “Many different designs of mass spectrometer are … used as detectors in all domains of food analysis, including quantitative analysis, qualitative screening analysis and profiling or characterization analysis,” says Richard Fussell, global marketing manager for the food and beverage market in the chromatography and mass spectrometry business at Thermo Fisher Scientific (Waltham, Mass.).
Supplement safety
Beyond oxilofrine, supplements contain other troublesome components that can be detected with MS. As Cody says, “Some ‘herbal supplements’ have been spiked with sildenafil, the active ingredient in Viagra!”
The list of offenses goes on. “A year ago, we were asked by a local news station to analyze a powdered drink that was being sold as a ‘sports supplement,’” Cody says. “A single scoop of this powder contained a caffeine dose equivalent to five cups of coffee, together with dimethylbutylamine—a compound with amphetamine-like properties—and yohimbine, a veterinary drug that can have unpredictable effects on blood pressure.” If someone consumed this before exercise, Cody says, “From my perspective, it was a heart attack in a can!”
No best MS
No type of MS fits all food applications. Combinations of gas chromatography, ion chromatography and liquid chromatography with MS are often used. These techniques, says Fussell, can be applied “for the targeted detection and quantification of low nanogram per gram concentrations of pesticides, veterinary medicines, processing contaminants, environmental contaminants, allergens and many other residues.”
AccuTOF-DART mass spectrum of the active ingredients in Chaga (Inonotus obliquus
), a fungus that grows on birch trees. Chaga is sold as a nutritional supplement and is believed to have health benefits. (Image courtesy of JEOL USA.)
The Waters Xevo G2-XS Quadrupole Time of Flight MS helps scientists explore the unknown with nontargeted analysis. (Image courtesy of Waters Corporation.)Different forms of MS add more opportunities. “High-resolution mass spectrometry—HRMS—and tandem mass spectrometry—MS/MS—provide additional information that increases the specificity of the analysis and helps to identify unknowns,” Cody says. “Inductively coupled plasma mass spectrometry—ICP/MS—is a valuable approach for elemental analysis, detecting traces of toxic metals such as lead and arsenic in foods and beverages.”
MS can also be used to analyze unknowns. “There is growing interest in using mass spectrometry with nontargeted acquisition to characterize or profile a sample either to solve a problem with a food product—a taint, or the presence of an unexpected contaminant—or to detect food fraud where a low-cost ingredient is substituted for a more expensive ingredient for the sole purpose of commercial gain, as was the case with the horse-meat crisis,” says Fussell. “Often nontargeted approaches are used in research to identify marker compounds that can be used subsequently to develop a more cost-effective targeted-acquisition method for routine control purposes.
When using a nontargeted approach, a scientist doesn’t need to have an idea of what a food sample might contain. “The generic nontargeted acquisition methods employed by time-of-flight and [Thermo Fisher Scientific] Orbitrap instruments acquire all of the information on all of the analytes all of the time,” Fussell says. “There is no need for preprogramming the system with a list of targets.”
Waters Xevo G2-XS Quadrupole Time of Flight MS and other platforms can also be applied to nontargeted analysis.
The ionization method used matters as well. In addition to DART, mentioned above, scientists can use matrix-assisted laser desorption ionization (MALDI). Cody says, “We used MALDI combined with time-of-flight tandem mass spectrometry to determine the structure of triglycerides in olive oil.”
Existing methods of ionization can also be modified. “Recently, we found that argon could be substituted for helium as the DART gas to provide complementary information,” Cody notes. “By introducing volatile solvents to the argon DART gas stream, we can selectively identify certain specific food compounds such as plant sterols, Vitamin E, lycopene in tomatoes and carotene in carrots.”
Ultimately, the best platform depends on the required data. Some projects focus primarily on identifying many analytes. Such applications, says Young, are being used by more companies as they “are challenged with protecting their brands from the occurrence of unexpected substances being found in their products by regulators or industry watchdogs.”
Advanced protection
Ongoing advances in MS analysis allow increasingly specific safety studies on foods. This often requires a combination of technologies. “Just one example that illustrates the value of combining HRMS with ion mobility can be found in recent work carried out by Waters scientists on fluoroquinolone antibiotic substances in foodstuffs,” Young explains. “Fluoroquinolones, such as ciprofloxacin, are zwitterionic amphoteric substances that have the ability to ionize at more than one location on the molecule.” The scientists separated the species—based on the location of the charge, which changes a molecule’s shape. “The importance of this lies in the fact that these different species can give rise to fragment ions and that the different species exist in different proportions depending on the conditions of the extract,” Young explains. “This could give rise to false findings of compliance of a foodstuff because of a misidentification.” This new approach helped scientists find antibiotic substances that were previously undetected in foods.
By combining today’s arsenal of MS and upstream methods, scientists can help us all eat the safest and most nutritious foods.
Reference
- Cohen, P.A.; Avula, B. et al. Pharmaceutical doses of the banned stimulant oxilofrine found in dietary supplements sold in the USA. Drug Testing and Analysis 2016; doi: 10.1002/dta.1976.
Mike May is a freelance writer and editor living in Florida. He can be reached at [email protected].