Location: Microbial and Chemical Food Safety
2022 Annual Report
Objectives
Objective 1: Transfer the QuEChERS mega-method to FSIS for the replacement of separate methods for pesticides, veterinary drugs, and other contaminants in foods.
Sub-objective 1A: Transfer the QuEChERSER mega-method.
Sub-objective 1B: Extend the QuEChERSER mega-method to plant and fungal toxins in pertinent matrices.
Sub-objective 1C: Conduct an inter-laboratory validation of the QuEChERSER mega-method.
Objective 2: Evaluate and compare triple quadrupole MS/MS analysis in both fast GC and UHPLC using high-resolution orbital ion trap MS/MS.
Sub-objective 2A: Directly compare results from shared final extracts by the different analytical methods.
Sub-objective 2B: Speed mega-method monitoring via 5 min each isocratic UHPLC with dual column switching backflushing and ITSP+LPGC MS-based analyses.
Objective 3: Develop novel multi-element analytical methods for heavy metals such as mercury, arsenic, cadmium, and lead in foods.
Sub-objective 3A: Develop volatile species generation (VSG) methods for determination of Pb and Cd in foods.
Sub-objective 3B: Achieve high productivity based on dual-mode VSG and pneumatic nebulization sample introduction.
Objective 4: Develop methods of analysis for emerging chemical contaminants not routinely monitored in FSIS regulated products.
Sub-objective 4A: Identify emerging contaminants, including food packaging chemicals that migrate into foods.
Sub-objective 4B: Validate QuEChERSER for targeted emerging contaminants found to be of concern in FSIS-regulated foods in Sub-objective 4A.
Sub-objective 4C: Conduct a market survey of food samples to study occurrence and levels of these contaminants to generate data for risk assessment.
Approach
Develop and transfer analytical technologies and methods to stakeholders that are effective and efficient for the screening, quantification and/or identification of chemical contaminants of concern in foods. Assist implementation to stakeholders of high-throughput monitoring for hundreds of pesticides, veterinary drugs, and environmental/emerging contaminants in the same sample extract in a matter of minutes using an automated process, including data handling and analyte identification. More specifically: 1) transfer the QuEChERS mega-method to USDA-FSIS for the replacement of separate methods for pesticides, veterinary drugs, and other contaminants in foods; 2) evaluate and compare triple quadrupole tandem mass spectrometry (MS) analysis in both fast gas chromatography and ultrahigh-performance liquid chromatography using high-resolution orbital ion trap MS/MS; 3) develop novel multi-element analytical methods for heavy metals such as mercury, arsenic, cadmium, and lead in foods; and 4) develop methods of analysis for emerging chemical contaminants not routinely monitored in FSIS-regulated products. The new methods and techniques will be validated to ensure their quality for reliable dissemination.
Progress Report
The investigators performed laboratory experiments to the full extent possible to substantially or fully meet the milestones for the year. Objective 4A was fully met as described in Accomplishments.
In Objectives 1 and 2, the QuEChERSER mega-method was validated in a major undertaking for >500 pesticides, veterinary drugs, environmental contaminants, and mycotoxins in hemp pellets, barley, and eggs. The study generated >1,000,000 data points for compilation, including comparisons between results using high-resolution mass spectrometry with orbital ion trap detection and triple quadrupole tandem mass spectrometry. The compilation has been completed for pesticides, environmental contaminants, and veterinary drugs, and manuscripts for publication are in preparation. Furthermore, technology transfer is underway for the USDA Food Safety and Inspection Service to consolidate their currently separate methods for pesticides and veterinary drugs into a single method based on QuEChERSER.
In Objective 3, an ultrasonic nebulizer was designed and built based on a 2.4 MHz piezoelectric transducer. High frequency vibration propagates through a 2 cm water layer to a 12.7 mm round polyethylene membrane. Sample solution delivered to the surface of this vibrating membrane is converted to a fine mist. An argon stream sweeps this mist to a dielectric barrier discharge zone where the sample aerosols are vaporized by the plasma. At 2.4 MHz, sample droplets have a narrow sub-micron size distribution, which do not stick to the wall of transport path or sink to the bottom of any container. An order of magnitude enhancement in sample introduction efficiency is expected vs. that of pneumatic nebulization. Furthermore, an underwater membrane desolvation system was conceived, designed, and built. The main objective is to turn wet aerosols to dry aerosols before the detection step. Moisture destabilizes an inductively-coupled plasma torch, hence compromising detection performance. Traditionally, desolvation is achieved by a heating-condensation-drying chain process. Thermoelectric heating is typically carried out at 110 degrees C, followed by condensation using a Graham or Allihn condenser. Finally, residual moisture is removed using a Nafion membrane tube. Such a system is costly, complicated, and bulky with a large dead volume. Our desolvation approach is to use two porous polytetrafluoroethylene membranes. The first is preloaded with a water layer, and the chamber below is pressurized above the water breakthrough pressure. Wet aerosols and gases are pushed through the membrane and the water layer. Droplets merge into the water layer and are removed from the stream. Dry aerosols, gases, and secondary droplets reach the second membrane without a water layer. The chamber below is pressurized to gas breakthrough pressure. Gases and solid particles freely pass through whereas droplets are blocked, allowing dry aerosols to be introduced into the torch for improved detection. The overall experimental setup is under construction, and the degree of completion is about 75%. This setup is suitable to both hydride-forming and non-hydride-forming elements. Target elements are lead and cadmium which suffer from low hydride generation efficiencies.
Accomplishments
1. Assessing chemical migration from paper and plastic food packaging with high resolution mass spectrometry. Potential contamination of food with chemicals migrating from food packaging is an important, yet under-investigated area of food safety. ARS scientists in Wyndmoor, Pennsylvania, examined chemicals migrating from common paper-based and plastic food packaging: pizza boxes, pizza box liners, butcher paper, liquid egg containers, plastic wrap, storage bags, vacuum bags, and meat trays. Gas and liquid chromatography separation systems coupled with the state-of-the-art high resolution mass spectrometry were utilized for comprehensive nontargeted screening of migrants. Overall, >250 migrated chemicals were identified, and most represented intentionally added substances, such as plasticizers, dyes, monomers, coatings, surfactants, lubricants, and others. Two chemicals of toxicological interest, bisphenols A and S, were identified and measured at levels below the established regulatory limits for migration, indicating no excessive risk to consumer health. The generated information about chemicals that migrate from food packaging samples is important to expand existing databases for their identification, contribute to risk assessment recommendations, and gain understanding of their identity, presence, and levels in food packaging.
Review Publications
Monteiro, S.H., Lehotay, S.J., Sapozhnikova, Y.V., Ninga, E., Moura Andrade, G.C., Lightfield, A.R. 2022. Validation of the QuEChERSER mega-method for the analysis of pesticides, veterinary drugs, and environmental contaminants in tilapia (Oreochromis Niloticus). Food Additives & Contaminants. Part A. 39:699-709. https://doi.org/10.1080/19440049.2021.2020911.
Sapozhnikova, Y.V., Taylor, R. 2022. Assessing chemical migration from plastic food packaging into food simulant by gas and liquid chromatography with high resolution mass spectrometry. Journal of Agricultural and Food Chemistry. https://doi.org/10.1021/acs.jafc.2c00736.
Hyeon-Woo, P., Chen, G., Hwang, C., Huang, L. 2020. Effect of water activity on inactivation of listeria monocytogenes using gaseous chlorine dioxide – A kinetic analysis. Food Microbiology. 95:103707. https://doi.org/10.1016/j.fm.2020.103707.
Lehotay, S.J., Lightfield, A.R. 2021. Comparison of four different multiclass, multiresidue sample preparation methods in the analysis of veterinary drugs in fish and other food matrices. Analytical and Bioanalytical Chemistry. 413:3223–3241. https://doi.org/10.1007/s00216-021-03259-x.
Yao, Z., Li, X., Liu, J., Mao, X., Chen, G. 2022. Ultratrace mercury speciation analysis in rice by on-line solid phase extraction-liquid chromatography-atomic fluorescence spectrometry. Journal of Food Analytical Methods. https://doi.org/10.1016/j.foodchem.2022.132116.
Ninga, E., Lehotay, S.J., Sapozhnikova, Y.V., Lightfield, A.R., Strahan, G.D., Monteiro, S.H. 2022. Analysis of pesticides, veterinary drugs, and environmental contaminants in goat and lamb by the QuEChERSER mega-method. Analytical Methods. 14:2761-2770. https://doi.org/10.1039/D2AY00713D.
Gu, S., Huang, X., Chen, M., Liu, J., Mao, X., Na, X., Chen, G., Shao, Y. 2021. Novel dielectric barrier discharge trap of arsenic introduced by electrothermal vaporization: the possible mechanism and its application. Analytical Chemistry. https://doi.org/10.1021/acs.analchem.1c03079.
Sapozhnikova, Y.V., Nunez, A. 2022. Non-targeted analysis with liquid chromatography - high resolution mass spectrometry for the identification of food packaging migrants. Journal of Chromatography A. https://doi.org/10.1016/j.chroma.2022.463215.
