Location: Microbial and Chemical Food Safety
2023 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
Objective 3: Pneumatic nebulization (PN) is the conventional sample introduction technique to inductively coupled plasma mass spectrometry (ICPMS). Although a low (1-3%) efficiency, PN is universally applicable to all elements. Photochemical vapor generation (PVG) enhances introduction efficiency for 1-2 dozen elements. PN-PVG dual-mode sample introduction gains advantages of both techniques. Thus far it has been implemented in two systems, one of which was granted an international patent. Unfortunately, both systems suffer from high noise that compromises performance. In one system, vapor bubbles segmented the effluent from the PVG reactor and interrupted nebulization. In another system, the PVG light source was dynamically attenuated by a liquid film on the lamp surface. In this work, the photoreactor was imbedded inside an ultraviolet (UV) light source, and a porous polytetrafluoroethylene (PTFE) membrane GLS was made to debubble the effluent and maintain a continuous flow to the nebulizer. Moderate to significant improvements in signal reproducibility were achieved for both PVG-active analytes (As, Se, Co, Pb, etc,) and PVG-inactive analytes (V, Ag, Tl, etc.). This invention led to the first low-noise PN-PVG dual-mode sample introduction system. A manuscript is currently on hold until the patent application is filed to the US patent and Trademark Office.
Organic matrix components may interfere with elemental analysis by inductively coupled plasma mass spectrometry. Matrix effects can be mitigated by thorough separation of target analytes from concomitant components at the cost of time, labor, and productivity. Under most circumstances, this correction strategy proves practical and effective. Common strategies include internal standardization calibration (ISC), matrix-matched calibration (MMC), standard addition calibration (SAC), and isotope dilution (ID). When mechanisms of interference are uncertain, or sample matrix cannot be closely matched, SAC is universally applicable. Because one calibration curve is needed for each sample, productivity suffers especially for large sample pools. In this work, a novel approach, matrix overcompensated calibration (MOC), was developed to correct matrix effects of carbon origin using fruit juices as model matrices and Ge, Rh, and Ir as internal standards. Ethanol is added to the samples at 5% as matrix markup to dominate matrix effects from native components. A standard series was treated likewise to construct a calibration curve. Unlike SAC, one calibration curve is applicable to all juices of diversified crop, geographical, and manufacturer origins. In this work, juices were diluted 1:50 in 1% HNO3-0.5% HCl-5% ethanol. MOC strategy enabled a simple dilute-and-shoot (DAS) protocol achieving quantitative recovery for model analytes As, Se, Cd, and Pb. Validation of this method was carried out by spike-recovery study and comparison with SAC and microwave-aided digestion (MAD). A manuscript is in preparation.
A dilute and shoot protocol was developed for multielemental (V, Ni, Co, Cu, Zn, As, Se, Ag, Cd, Ba, and Pb) analysis in fruit juices by ICPMS. Fruit juices were diluted in 1:50 ratio in 1% HNO3¿0.5% HCl¿5% ethanol. Ethanol was added as a matrix markup to all samples and a standard series to overwhelm native matrix components in terms of matrix effects. This MOC strategy effectively corrected matrix effects of carbon origin, achieving quantitative (92-102%) recovery and accurate quantitation comparable to traditional SAC. Ge, Rh, and Ir were used as internal standards. Quantification results agreed well to those by complete microwave-aided digestion (MAD). Because a single calibration curve applied to all juices of diversified crop, geographic, and manufacturer origins, MOC gained significant advantages in time, labor, productivity, and argon consumption. A manuscript is in preparation.
Accomplishments
1. Novel method for arsenic in rice. The high toxicity of inorganic arsenic (iAs) makes its analysis very important, particularly in rice and rice products. To improve the analysis, ARS scientists in Wyndmoor, Pennsylvania, applied electrospinning technology to fabricate novel covalent organic framework (COF) composite nanofiber membranes, which serve as strong anion exchange sorbents of iAs. The finished membranes were characterized, and key parameters of pipette-tip solid-phase extraction procedures were investigated. The iAs was successfully separated from rice matrix and quantified by hydride generation-atomic fluorescence spectrometry. This methodology achieved an iAs detection limit of 0.015 ng/mL, 87-99% recoveries, and greater than 5% relative standard deviation, which should prove adequate for routine monitoring by regulatory and industry laboratories in the future.
2. Analysis of per- and polyfluoroalkyl substances (PFAS) “forever chemicals" in foods. Per- and polyfluoroalkyl substances (PFAS) are known as "forever chemicals" due to their persistence, ability to bioaccumulate, and toxicity. Diet has been considered a major source of PFAS exposure, however, efficient analytical methods for their measurement in foods are lacking. ARS scientists in Wyndmoor, Pennsylvania, developed a new method for analysis of 34 PFAS in foods regulated by the USDA Food Safety Inspection Service (FSIS): chicken, pork, beef, catfish, and liquid eggs. The developed method is fast and simple, and outperformed two official methods from the US Food and Drug Administration (FDA) and USDA FSIS. The validation results demonstrated the method's robustness, accuracy, and precision. This method can easily be implemented for routine use in laboratories already analyzing pesticides, veterinary drugs, and environmental contaminants.
3. Investigating migration potential of a new rechargeable antimicrobial coating for food processing equipment. Development of novel efficient and low-cost technologies for food contact surfaces remains a big challenge in food safety. Before a new coating material can be introduced to the market for direct food contact applications, studies must be performed to determine safety and avoid contamination of food with the components of the food contact material. ARS scientists in Wyndmoor, Pennsylvania, in collaboration with industrial partners, evaluated the chemical safety of a novel antimicrobial polymer coating for use on food processing equipment. Migration of active chemical components from a new N-halamine antimicrobial coating was investigated to determine their migration levels. This study resulted in the first report on chemical migration from an N-halamine antimicrobial polymer coating product to inform potential consumer exposure.
4. Development of an improved cleanup method for analysis of contaminants in foods. Monitoring of pesticides and environmental contaminants in foods is a common application worldwide for food safety and other purposes among regulatory agencies, food and agricultural industries, consumer groups, and academia. Development of ever faster, more efficient, and higher quality analytical methods with broader scope better meets monitoring needs, and automated cleanup of initial food extracts prior to advanced instrumental analysis is one of the best ways to accomplish this goal. In this study, an improved robotic method was developed using a new mini-cartridge design for sample cleanup in the analysis of more than 250 pesticides and environmental contaminants at ultratrace levels in different types of foods. This procedure has been integrated into the QuEChERSER mega-method to save time, increase sample throughput, and yield more reliable results in routine monitoring laboratories. At least three companies are now selling this product internationally and marketing the cleanup conditions for usage developed by the ARS scientists in Wyndmoor, Pennsylvania.
Review Publications
Sapozhnikova, Y.V. 2022. Liquid and gas chromatography – mass spectrometry methods in food and environmental safety. In: Pico, Y., Campo, J., editors. Mass Spectrometry in Food and Environmental Chemistry. The Handbook of Environmental Chemistry. New York, NY: Springer. p. 127-143.
Taylor, R., Sapozhnikova, Y.V., Demir-Grubbs, B., Qiao, M. 2023. Investigating migration potential of a new rechargeable antimicrobial coating for food processing equipment. Food Additives & Contaminants. Part A. 40(5):688-697. https://doi.org/10.1080/19440049.2023.2203777.
Taylor, R., Sapozhnikova, Y.V. 2022. Comparison and validation of the QuEChERSER mega-method for determination of per- and polyfluoroalkyl substances in foods by liquid chromatography with high-resolution and triple quadrupole mass spectrometry. Analytica Chimica Acta. 1230(16):340400. https://doi.org/10.1016/j.aca.2022.340400.
