Perspective Cite This: J. Agric. Food Chem. 2018, 66, 9573−9581
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Perspectives on Liquid Chromatography−High-Resolution Mass Spectrometry for Pesticide Screening in Foods Jon W. Wong,*,† Jian Wang,‡ Willis Chow,‡ Roland Carlson,§ Zhengwei Jia,∥,⊥ Kai Zhang,† Douglas G. Hayward,† and James S. Chang#
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†
Center for Food Safety and Applied Nutrition, United States Food and Drug Administration, 5001 Campus Drive, College Park, Maryland 20740, United States ‡ Calgary Laboratory, Canadian Food Inspection Agency, 3650 36th Street Northwest, Calgary, Alberta T2L 2L1, Canada § Center for Analytical Chemistry, California Department of Food and Agriculture, 3292 Meadowview Road, Sacramento, California 95832, United States ∥ Shanghai Institute for Food and Drug Control (SIFDC), 1500 Zhangheng Road, Shanghai 210203, People’s Republic of China # Thermo Fisher Scientific, 355 River Oaks Parkway, San Jose, California 95134, United States S Supporting Information *
ABSTRACT: This perspective discusses the use of liquid chromatography coupled with high-resolution mass spectrometry (LC−HRMS) for multiresidue analysis of pesticides in foods and agricultural commodities. HRMS has the important distinction and advantage of mass-resolving power and, therefore, requires different concepts, experiments, and guidance for screening, identification, and quantitation of pesticides in complex food matrices over triple quadrupole mass spectrometry. HRMS approaches for pesticide screening, including full-scan experiments in conjunction with tandem mass spectrometry (MS/MS) experiments, are described. This approach results in the generation of chromatographic retention times and highresolution mass spectra with accurate mass measurements that can be used to create compound databases. New data processing tools can create an efficient and optimized screening approach that can speed the analysis and identification of compounds, reduce the need for chemical standards, and harmonize pesticide analytical procedures. KEYWORDS: liquid chromatography−high-resolution mass spectrometry (LC−HRMS), non-target data acquisition target analysis (nDATA), pesticide screening, data independent acquisition (DIA), data dependent acquisition (DDA), multiresidue pesticide analysis
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INTRODUCTION Pesticides are used to increase crop yields by protecting crops against pests. These chemicals are globally regulated by countries and governing organizations by establishing tolerances to ensure that they are used at safe levels when applied to foods. There are close to 1000 pesticides that could potentially be used on crops. The challenge is the ability to economically analyze for the presence of these chemicals, their metabolites, and degradation products when precise knowledge of pesticide application or misuse is lacking. This has led to the development and implementation of multiresidue pesticide methods that typically involve extraction/partition, sample cleanup, and instrumental analysis to incorporate as many pesticide classes as possible in a single procedure. Today’s comprehensive pesticide analysis involves the use of both gas and liquid chromatography coupled to mass spectrometry (GC−MS and LC−MS) as highly sensitive and selective methods for targeted analysis of pesticides.
chromatography coupled to a triple quadrupole (QqQ) mass spectrometer with electrospray ionization (ESI) are the most common instruments used for multiresidue pesticide analysis in foods. Single quadrupole instruments in pesticide analysis usually operate in selective ion monitoring (SIM) mode, which rely on the detection of selected precursors and primarily fragment ions (produced via EI) associated with the targeted analyte of interest. More selective than SIM, a triple quadrupole mass analyzer can perform a tandem mass spectrometry (MS/ MS) scan by operating in selected (or multiple) reaction monitoring (SRM or MRM) mode. In MS/MS mode, the background as a result of the presence of isobaric compounds is significantly reduced to increase the signal-to-noise ratio and only the acquisition of product ions being formed from the selected precursor ions are being monitored and detected. This is illustrated in Figure 1. In GC−MS/MS or LC−MS/MS, the pesticide analyte is separated from other components in the mixture by chromatography, followed by ionization in the ion source, and the charged analyte (precursor) enters the mass analyzer, where the precursor is selected in the first quadrupole
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CHROMATOGRAPHY−TRIPLE QUADRUPOLE MASS SPECTROMETRY: CURRENT AND STANDARD PROCEDURES FOR PESTICIDE ANALYSIS Gas chromatography coupled to single or triple quadrupole mass spectrometry with electron impact ionization (EI) and liquid © 2018 American Chemical Society
Received: Revised: Accepted: Published: 9573
July 2, 2018 August 24, 2018 August 31, 2018 August 31, 2018 DOI: 10.1021/acs.jafc.8b03468 J. Agric. Food Chem. 2018, 66, 9573−9581
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Figure 1. LC−QqQ−MS operating in MS/MS mode.
[or first MS stage (MS1)] from a targeted list. The precursor undergoes fragmentation via collision-induced dissociation in the collision cell (formerly the second quadrupole) to produce product or fragment ions. The resulting product ion characteristics of the pesticide analyte are then pre-selected by the third quadrupole [or second MS stage (MS2)] and detected. Typically, two precursor-to-product transitions are used for quantitation and identification; the more dominant transition for quantitation and the ratio of second to first transition are often compared to a reference standard. Optimized multiresidue pesticide methods consist of MS/MS scans that are sensitive, selective, and provide quantitation and identification for hundreds of the pesticides in one injection. All multiresidue pesticide methods use this targeted MS/MS approach on triple quadrupole instruments.1−4 However, these SRM procedures have their limitations in analyzing so many potential pesticide targets in a wide variety of food matrices. The development of these methods requires management of chromatographic and mass spectrometric parameters, such as retention times, precursor ions, MS/MS product transitions, and their collision energies, to optimize the detection of the targeted analyte. GC− MS/MS and LC−MS/MS are a priori approaches, requiring characteristic information on the pesticide analytes that must be built into the MS/MS target or inclusion list, so that they can be detected and analyzed. These approaches will not be able to detect the presence of other pesticide analytes if they are not included in the target or inclusion list.
mass measurements with MS/MS confirmation. In non-targeted approaches, retroactive or retrospective analysis (a topic for future discussion or perspective) can be performed to analyze additional pesticides and other chemicals that were not identified the first time that the food sample was analyzed. Modern quadrupole−HRMS instruments offer different opportunities and approaches over SRM approaches (shown in Figure 1) performed by triple quadrupole or hybrid quadrupole− linear ion trap (QqLIT) platforms, such as data-dependent (DDA) and data-independent acquisitions (DIA; Figures 2−4). Previous interest in DDA [also known as information-dependent acquisition (IDA)] was demonstrated by the use of highperformance liquid chromatography coupled with QqLIT mass spectrometry to produce mass spectral libraries for the analysis of pesticides in fruits and vegetables.6 Although the work was successful in generating data-dependent MS/MS scans, there were some deficiencies because the unit mass resolution of precursor and product ions could not provide unambiguous identification of pesticides when comparing experimental MS/ MS results against the library results. Earlier studies performed by Wang et al.1,7 used full-scan HRMS (FS-HRMS) and datadependent high-resolution MS/MS (dd-HR MS/MS) scans using ultrahigh-performance liquid chromatography−positive electrospray ionization−quadrupole time-of-flight mass spectrometry [UHPLC−ESI(+)−QTOF] to analyze 138 pesticides in fruits and vegetables. Although the precursor sensitivity in the FS-HRMS was adequate for the detection of pesticides at the 10 μg/kg level, HR MS/MS was less sensitive and was separately performed for identification purposes in early generation QTOF instruments. Current QTOFs and QOrbitraps are more sensitive than their predecessors as a result of faster electronics, enhanced ion optics, and improved detector technologies.8 Recently, the use of FSHRMS/dd-HR MS/MS using UHPLC−QOrbitrap mass spectrometry was successfully used for multiresidue pesticide analysis.9 Although not all DDA experiments are targeted, the acquisition as illustrated in Figure 2 is coupled to a target or inclusion list of ions and their corresponding retention time windows. The acquisition initially performs in FS-HRMS mode until a precursor ion from the inclusion list is detected above an intensity threshold, triggering a HR MS/MS scan. Once the dd-HR MS/MS scan is complete, the acquisition returns to FS-HRMS until the next ion on the inclusion list is detected. The method performance of the HRMS procedure, including overall recovery, intermediate precision, and measurement uncertainty, was evaluated for 451 pesticides. For the 10 fruit and vegetable matrices studied, 94% of the pesticides in fruits and 91% of the pesticides in vegetables had recoveries between 81 and 110%, 99% of the pesticides in fruits and 99% of the pesticides in vegetables had an intermediate precision of ≤20%, and 98% of the pesticides in fruits and 96% of the pesticides in vegetables showed measurement uncertainty of ≤50%. Overall, the UHPLC−ESI(+)−QOrbitrap demonstrated acceptable performance for the quantification of pesticide residues in fruits
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HIGH-RESOLUTION MASS SPECTROMETRY (HRMS): NEW CONCEPTS FOR PESTICIDE ANALYSIS In the last 15 years, food safety laboratories have evaluated the use of gas and liquid chromatography−high-resolution mass spectrometry (GC−HRMS and LC−HRMS) for the analysis of pesticides and other chemical residues, contaminants, and toxins that may be present in foods. Although there are single-stage time-of-flight (TOF) and Orbitrap mass analyzers commercially available, they have limitations and can only operate in full-scan mode. The single-stage Orbitrap mass analyzer does consist of a high-energy collisional dissociation (HCD) cell that can produce fragmentation, but without a quadrupole, there is no precursor ion selection. This procedure is known as all-ion fragmentation (AIF), and because all precursor ions formed in the ion source are subjected to fragmentation without discrimination, the resulting MS/MS spectra lack specificity as a result of interfering and co-eluting matrix components.5 The work on HRMS has been primarily focused on LC−HRMS because most of the advancement on HRMS originated from protein chemistry and proteomics. The implementation of hybrid high-resolution mass spectrometers [i.e., quadrupole time of flight (QTOF) and quadrupole Orbitrap (QOrbitrap)] offers an advantage over singlestage analyzers in that both full MS and MS/MS scans can be achieved in a single injection, providing high-resolution accurate 9574
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Figure 2. Liquid chromatography−full scan coupled with data-dependent acquisition mass spectrometry (UHPLC−FS-HRMS/dd-HR MS/MS), in this example, consists of a defined list (inclusion list) of precursor ions and their corresponding retention time windows. During LC−MS analysis, the acquisition is initially performed in full-scan MS mode, and if the scan detects any of the precursor ions from the inclusion list at a set intensity threshold, the mass spectrometer is triggered to perform a MS/MS scan. The instrument returns to full-scan mode after the MS/MS task is accomplished and will return to MS/MS mode once it detects the next precursor ion on the inclusion list. If the HRMS has an Orbitrap as the mass analyzer, the C-trap controls the flow of ions between the quadrupole, HCD cell, and Orbitrap. Note some of the precursors may be separated chromatographically; therefore, not all ions are present at the defined retention time.
weight range of m/z 200−500 and the smaller windows provide better selectivity of the precursors to undergo MS/MS fragmentation. The disadvantage of DIA is the long cycle time, which limits the number of data points that define the chromatographic peak shapes and may not be reliable for quantitation. The DIA-HR MS/MS spectra are more complex than dd-HR MS/MS spectra as a result of the larger isolation windows, allowing for matrix interferants of the same mass range to undergo fragmentation along with the analytes of interest. The vDIA experiment was initially developed for protein analysis but Zomer and Mol,17 demonstrated a FS-HRMS/ vDIA-HR MS/MS procedure for the analysis of pesticides in fruits and vegetables. Wang et al.18 expanded the procedure and developed a more comprehensive compound database for the screening of 448 pesticides for the analysis of fruit and vegetable matrices fortified with pesticides at 10 and 100 μg/kg. The validated screening method is capable of screening at least 94 and 99% of 448 pesticides at 10 and 100 μg/kg, respectively, in fruits and vegetables without having to evaluate every compound manually during data processing, which significantly reduced the workload in routine practice. Goon et al.19 and Rajski et al.20 have also successfully demonstrated the capabilities and effectiveness of vDIA acquisition using consecutive variable mass window fragmentation events for the analysis of 199 and 166 pesticides in spices and fruit/vegetables, respectively. DIA can come in other versions, such as multiplex DIA (mDIA).21 In mDIA, the precursor ions that fall within a selected number of mass windows are subject to fragmentation and simultaneous detection of the product ions. Wang et al.22 demonstrated the use of a FS-HRMS/mDIA-HR MS/MS experiment using an UHPLC−QOrbitrap MS platform for the
and vegetables. A recent HRMS quantitative approach, parallel reaction monitoring (PRM), originally developed for proteomics applications, became available for both QOrbitrap and QTOF platforms.10,11 PRM on a HRMS analyzer is very similar to SRM (MRM) on a QqQ, such that the precursor ion is isolated in the quadrupole for fragmentation in the collision cell and the resulting product ions are detected in the HR mass analyzer. PRM differentiates from targeted DDA and unit mass SRM because the signal intensities of the product ions with high mass accuracies can be used for quantitation.12 UHPLC−FS-HRMS coupled with data-independent acquisition mass spectrometry (DIA-HR MS/MS) is a non-targeted procedure that combines the advantages of SRM and DDA.13 DIA was performed on an ion trap14 and is also known as sequential window acquisition of all theoretical mass spectra (SWATH)15 or MSE,16 when it is performed on a QTOF platform. UHPLC−FS-HRMS/DIA-HR MS/MS consists of fragmentation events based on segmented mass isolation windows to cover the entire range sequentially of all precursor ions of interest. The advantage of DIA is that it does not require any prior information about the precursors, all ions within the mass range undergo fragmentation, and fragmentation is retention-time-independent. As shown in the DIA experiment in Figure 3, acquisition is initially performed in FS-HRMS mode from m/z 100 to 1000, followed by segmented mass isolation windows of m/z 25 wide from m/z 100 to 500 and m/z 100 wide from m/z 600 to 1000. Because there are different segmented mass isolation windows (m/z 25 and 100 in the example shown in Figure 3), this is referred to as a variable DIA (vDIA) experiment. The advantage for having variable segmented mass isolation windows is that most pesticides fall within a molecular 9575
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Figure 3. Liquid chromatography−full scan coupled with variable data-independent acquisition mass spectrometry (UHPLC−FS-HRMS/vDIA HR MS/MS) consists of fragmentation events based on segmented mass isolation windows to cover the range of precursor ions. Acquisition is initially performed in full-scan MS mode (m/z 100−1000), followed by variable segmented ranges of m/z 25 (m/z 100−500) and m/z 100 (m/z 500−900), and returns to full scan after the cycle is completed. This figure was adapted with permission from ref 45. Copyright 2014 LabX Media Group.
Figure 4. In multiplexed DIA acquisition (UHPLC−FS-HRMS/mDIA HR MS/MS), a full-scan MS (m/z 100−1000) is first completed, followed by fragmentation events based on mass isolation windows of m/z 50 wide. After HRMS isolates the analytes from m/z 100 to 500 for MS/MS analysis, four mass windows (m/z 500−550, 600−650, 700−750, and 800−850) are selected and the analytes within those defined masses from each window are subjected to fragmentation and detection of all of the product ions simultaneously. This is followed by the next set of four mass windows (m/z 550−650, 650−700, 750−800, and 850−900) to undergo simultaneous fragmentation and detection before completing the cycle and returning to full-scan mode. This figure was adapted with permission from ref 45. Copyright 2014 LabX Media Group.
mDIA consists of 10 loop counts and 4 multiplex counts. For loop counts 1−8, a collection of ions isolated by the quadrupole at every m/z 50 mass increment from m/z 100 to 500 are sent to
analysis of veterinary drugs in milk. From the example illustrated in Figure 4, a FS-HRMS is performed from m/z 100 to 1000, followed by mDIA-HR MS/MS from m/z 100 to 900. The 9576
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in the database. The software and database search resulted in the identification of griseofulvin, an antifungal medication present in the tomatillo sample. Panels A and B of Figure 5 illustrate the comparisons of the extracted ion chromatograms (XICs) from FS-HRMS and dd-HR MS/MS scans and the dd-HR MS/MS spectrum obtained from the tomatillo extract and griseofulvin standard, respectively. Retention times are a close match (4.69 versus 4.70 min), and five ions, including the protonated molecular ion m/z 353.07864 and four product ions m/z 285.05243, 215.01056, 165.0562, and 69.03349, in the tomatillo extract are a match to the griseofulvin standard within the ±5 ppm mass accuracies of the calculated precursor and product ions stored in the database. The tomatillo sample extract could also be easily screened in DIA, and the results are compared to the DDAgenerated compound database as well. It is suspected, although not confirmed, that the presence of griseofulvin could have been a result of a mold contamination in the tomatillo.29,30 The optimization of the software and compound databases can reduce or eliminate false positives and false negatives in screening applications.31 For the UHPLC−FS-HRMS/vDIAHR MS/MS studies, the accurate mass, retention time, and response threshold were three parameters in the compound database that were used to detect incurred pesticide residues in samples. The concepts and practical aspects of in-spectrum mass correction or solvent background lock-mass correction, retention time alignment, and response threshold adjustment were evaluated and integrated into a functional and working compound database for the targeted screening of pesticides with MS/MS identification. The default settings for the threshold in the compound database are typically not optimized because it requires experimental results for all pesticide entries in the database. If the default settings are set too low, this could increase the number of false positives as a result of peak interferences from a noisy baseline that is above the response threshold and potential column carryover. If the default settings are set too high, the screening results may lead to an increase in the number of false negatives because signals from the contributing pesticide are below the signal threshold and will go undetected. Response threshold values of each pesticide are determined by results obtained from the analysis of pesticide standards equivalent to 10 ppb (5 μg/L standard) of the pesticide in the food and analyzed by UHPLC−FS-HRMS/dd-HR MS/MS. However, complicating the situation is that most LC−MS applications use electrospray ionization and are susceptible to matrix effects, primarily ion suppression. With reliance on experience with QuEChERS extracts of various plant foods and their LC− MS/MS responses, a value based on 10% of the peak area response of a 5 μg/L standard was used as an estimate threshold response for the pesticide in the compound database. This improves the efficiency and effectiveness of the software and the compound database for screening applications. A substantial investment of resources and time are required to build a comprehensive database, and some pesticide standards may not be commercially available. However, once a database has been developed, established, and properly maintained, it can be implemented in any laboratory and expanded to include other pesticides, assuming that the same HRMS platform is being used.
the collision cell for fragmentation and the resulting products are scanned out for detection in the Orbitrap or TOF. For loop count 9 and a multiplex count of 4, a collection of ions isolated by the quadrupole for mass ranges in segments of m/z 500−550, 600−650, 700−750, and 800−850 were sent to the collision cell sequentially for fragmentation. The collected product ions were then sent to the Orbitrap (via the C-trap) or TOF and simultaneously detected. The process is continued with the next loop count of 10 and multiplex count of 4 for the mass ranges in segments of m/z 550−600, 650−700, 750−800, and 850−900, and again, these ions are sent to the collision cell for fragmentation. The product ions are then sent to the Orbitrap or TOF mass analyzer for detection. Another cycle begins by returning to FS-HRMS, followed by the loop counts 1−8 and the two nonoverlapping windows each containing the four mass segments. This mDIA experiment was evaluated to screen for veterinary drugs in milk but was also developed to demonstrate its equivalence to vDIA for pesticide screening.
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LC−HRMS SCREENING USING COMPOUND DATABASES AND SOFTWARE TOOLS Software tools and compound databases are used for routine residue screening of pesticides in foods using the targeted and non-targeted screening modes discussed in the previous sections. A compound database is a collection of chromatographic and mass spectral information, such as retention times, precursor and product ions, signal thresholds, and/or any relevant information on compounds that may be useful in software searching and information retrieval for identification purposes.23 Identification of pesticides is achieved by comparing experimental results to the results that were obtained from authentic standards and stored in a compound database. Various agencies, such as the United States Food and Drug Administration (U.S. FDA),24 European Union Reference Laboratories for Residues of Pesticides,25 and Codex Alimentarius,26 have established criteria guidelines or recommendations for the identification of pesticides in foods using mass spectrometry coupled to chromatography. Identification of the pesticide by LC−HRMS involves chromatographic retention time and the presence of at least two ions (preferably one being the molecular ion and at least one product ion) with a mass accuracy within ±5 or 10 ppm. Software tools provided by HRMS instrument manufacturers can be set up to screen samples and identify pesticides using these identification criteria. UHPLC−ESI(+)− QOrbitrap FS-HRMS/dd-HR MS/MS was used to analyze the tomatillo extract prepared by the commonly used pesticide procedure known as QuEChERS.27,28 A compound database was generated for 603 pesticides by the analysis of authentic pesticide standards using UHPLC−ESI(+)−QOrbitrap FSHRMS/dd-HR MS/MS to provide the chromatographic retention times and calculated product masses obtained from the experimental values of the MS/MS spectra. Calculated product masses were determined on the basis of the proposed product structures elucidated by fragmentation software (MassFrontier 7.0). The database and accompanying MS/MS spectra are provided in Table S1 and Figure S1 of the Supporting Information. Screening of the tomatillo extract was performed using the HRMS software (TraceFinder) and the pesticide compound database. The criteria for identification is incorporated in the software through matching the experimental UHPLC retention times and the extracted masses of the precursor (such as the protonated or ammoniated molecular ion) and product ions with mass accuracies of ±5 ppm with the pesticide entries stored
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SCREENING APPROACHES FOR OTHER RESIDUES, TOXINS, AND CONTAMINANTS The use of LC−HRMS applications has not only been applied to pesticides but to veterinary drugs in milk and mycotoxins in cereal grains and nuts using UHPLC−ESI(+)−QOrbitrap 9577
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Figure 5. Griseofulvin present in (A) tomatillo and (B) standard as analyzed by UHPLC−FS-HRMS/dd-HR MS/MS. The XICs used the extracted mass of [M + H]+ = 353.07864, dd-HR MS/MS scan, and the resulting dd-HR MS/MS spectrum. The mass accuracy, δM, is defined as (mexp − mcalc)/ mcalc × 106, where mexp and mcalc are the experimental and calculated masses, respectively, of precursor and product masses. Theoretical structure assignments are proposed for each chemical fragment. 9578
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Journal of Agricultural and Food Chemistry FS-HRMS/dd-HR MS/MS approaches.22,32 As mentioned earlier, a procedure for the analysis of veterinary drugs in milk using mDIA approaches was also created, which indicates that the procedures from different chemical classes could potentially be combined into a single generic procedure for LC−HRMS analysis. Similar approaches using chromatographic approaches combined with HRMS for small-molecule (i.e., non-protein chemicals) screening in other disciplines, such as forensic toxicology (drug testing and suspected poisoning), illegal chemicals in complex matrices, and chemical contaminants in environmental systems, have also been developed and demonstrated with promising success.31,33−37 These other fields have similar challenges or advancements, such as the development of optimized chromatography−high-resolution mass spectrometry approaches, need for advanced computer-based tools for screening complex data sets, creation and management of compound databases and MS/MS spectral libraries, availability and accessibility to small-molecule databases, such as MassBank,38,39 and alternatives to experimentally created databases, such as the use of in silico fragmentation, where no database entry is available for a compound. Currently, there is no single method that can universally screen for every pesticide type in a single injection. There are pesticides that perform better under negative electrospray ionization conditions and classes of polar, acidic, ionic, metallic, and gaseous pesticides that are not compatible to a nonpolar, multiresidue pesticide procedure. There is also a GC−MS component to analyze pesticides not amenable to LC−MS analysis. The use of GC−HRMS coupled to a QTOF or QOrbitrap for screening applications has also been investigated.40,41 Most GC−quadrupole−HRMS platforms are limited to just EI that do not generate molecular precursor ions, therefore preventing the use of HRMS/MS experiments and database searching workflows for screening applications. However, Portolés et al.42 and Cheng et al.43 were able to generate whole molecular ion precursors in the absence or presence of water to generate molecular ions by charge transfer or protonation, which allowed them to conduct MSE experiments on a GC−QTOF−MS platform equipped with an atmospheric pressure ionization source. Fifteen years ago, Klein and Alder44 demonstrated the monumental feat of screening and quantitating 100 pesticides in various crops by LC−MS/MS. We anticipate with separation methods coupled to HRMS, databases, and software tools, the number of screen pesticides will increase at least 10-fold in the near future. Currently, the non-target data acquisition and target analysis (nDATA) approach utilizing UHPLC− HR MS/MS-DIA and compound databases will continue to be applied to not only pesticides but also other residues and contaminants for screening and analysis in various foods. Improvements and advances in hardware UHPLC and HRMS technologies, software tools and approaches, availability of larger and expandable databases, experience and increased knowledge of the technologies, and improvement in the skill set will expand and advance the field further. The development of a high-throughput procedure to simultaneously screen, identify, and quantitate residues, contaminants, and other important chemicals in foods will be the next ideal accomplishment.
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Data-dependent MS/MS spectra of 603 pesticides (Figure S1) (PDF) Precursor and product masses of 603 pesticides (Table S1) (XLSX)
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Jon W. Wong: 0000-0003-0116-2880 Kai Zhang: 0000-0001-5668-9458 Douglas G. Hayward: 0000-0003-3063-1623 Present Address ⊥
Zhengwei Jia: Waters Technologies, Block 13 City of Elite, 1000 Jinhai Road, Pudong New District, Shanghai 201206, People’s Republic of China. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The authors acknowledge the United States Environmental Protection Agency National Pesticide Standard Repository for providing much of the pesticide standards required to build the pesticide compound database, Dr. Christine Parker [United States Food and Drug Administration (U.S. FDA)] for a critical review of this perspective, and James B. Wittenberg (formerly at the U.S. FDA, now at the Alcohol and Tobacco Tax and Trade Bureau) for the drawing of the figures. The authors appreciate the staff at The Scientist for Figures 3 and 4 to provide the inspiration for the visual illustration of the full-scan MS/vDIA MS/MS and full-scan MS/mDIA MS/MS workflows, respectively. Some of the work described in this perspective was a result of a collaborative research agreement between the U.S. FDA and the Canadian Food Inspection Agency.
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REFERENCES
(1) Wang, J.; Leung, D. Applications of ultra-performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry on analysis of 138 pesticides in fruit- and vegetable-based infant foods. J. Agric. Food Chem. 2009, 57, 2162−2173. (2) Wong, J. W.; Zhang, K.; Tech, K.; Hayward, D. G.; Makovi, C. M.; Krynitsky, A. J.; Schenck, F. J.; Banerjee, K.; Dasgupta, S.; Brown, D. Multiresidue pesticide analysis in fresh produce by capillary gas chromatography−mass spectrometry/selective ion monitoring (GC− MS/SIM) and -tandem mass spectrometry (GC−MS/MS). J. Agric. Food Chem. 2010, 58 (10), 5868−5883. (3) Zhang, K.; Wong, J. W.; Yang, P.; Tech, K.; Dibenedetto, A. L.; Lee, N. S.; Hayward, D. G.; Makovi, C. M.; Krynitsky, A. J.; Banerjee, K.; Jao, L.; Dasgupta, S.; Smoker, M. S.; Simonds, R.; Schreiber, A. Multiresidue pesticide analysis of agricultural commodities using acetonitrile salt-out extraction, dispersive solid-phase sample cleanup, and high performance liquid chromatography−tandem mass spectrometry. J. Agric. Food Chem. 2011, 59 (14), 7636−7646. (4) Hayward, D. G.; Wong, J. W.; Shi, F.; Zhang, K.; Lee, N. S.; DiBenedetto, A. L.; Hengel, M. J. Multiresidue pesticide analysis of botanical dietary supplements using salt-out acetonitrile extraction, solid-phase extraction cleanup column, and gas chromatography−triple quadrupole mass spectrometry. Anal. Chem. 2013, 85 (9), 4686−4939. (5) Zhu, X.; Chen, Y.; Subramanian, R. Comparison of informationdependent acquisition, SWATH, and MSALL techniques in metabolite identification study employing ultrahigh-performance liquid chromatography−quadrupole time-of-flight mass spectrometry. Anal. Chem. 2014, 86, 1202−1209.
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jafc.8b03468. 9579
DOI: 10.1021/acs.jafc.8b03468 J. Agric. Food Chem. 2018, 66, 9573−9581
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