Analytical performance of feline plasma on current Heska and IDEXX point-of-care biochemistry analyzers compared with a commercial laboratory analyzer.

BACKGROUND: Point-of-care (POC) biochemistry analyzers are widely used in small animal clinical practice but infrequently independently assessed for performance. OBJECTIVE: To assess the performance of two current model point-of-care biochemistry analyzers (Heska Element DC and IDEXX Catalyst) compared with a commercial laboratory analyzer (Cobas 8000). METHODS: One hundred twenty-one cats from a feline hospital population were sampled with plasma results from a single lithium heparin tube assessed on all three analyzers. Plasma biochemistry results from each POC analyzer were compared with the commercial laboratory analyzer using Bland-Altman difference plots and by determining whether the limits of agreement (LOAs) (95% of differences) fell within various quality goals after correcting for inherent bias. RESULTS: Only 7 of 14 analytes on the Heska analyzer and 2 analytes on the IDEXX analyzer attained the most stringent LOA quality goal, which was being within desirable total error based on biologic variation (TEdes ). The number of analytes achieving quality goals increased with less stringent standards such as American Society of Veterinary Clinical Pathologists allowable total error (ASVCP TEA ) guidelines or if <95% of clinical comparisons reaching these quality goals is considered acceptable. Widespread bias was found between both POC analyzers and the commercial laboratory analyzer. CONCLUSIONS: The performance of both POC biochemistry analyzers was variable compared with a commercial laboratory analyzer. Performance goals were only able to be attained after the bias for each analyzer was accounted for by offsetting the LOAs and quality goals set by the mean bias for each analyte on each analyzer.

Lipoprotein profiles in Miniature Schnauzer dogs with idiopathic hypertriglyceridemia and hypercortisolism.

Miniature Schnauzer dogs (MSs) are predisposed to both idiopathic hypertriglyceridemia (iHTG) and hypercortisolism (HCort). To our knowledge, the lipoprotein profiles of MSs with iHTG have not been compared to those with HCort. We analyzed cholesterol and triglyceride concentrations and lipoprotein fractions in 4 groups of MSs: normotriglyceridemia (NTG) without concurrent disease (Healthy-NTG), HCort and NTG (HCort-NTG), HCort and HTG (HCort-HTG), and iHTG. Lipoprotein fractions were assessed by lipoprotein electrophoresis and compared between groups. Fifty-one plasma samples were analyzed. Twenty-five dogs had NTG (16 Healthy-NTG, 9 HCort-NTG) and 26 dogs had HTG (7 iHTG, 19 HCort-HTG). Dogs with iHTG or HCort-HTG had significantly higher cholesterol concentrations than Healthy-NTG dogs. Dogs with HCort-HTG had higher cholesterol than HCort-NTG dogs. There was a significantly higher low-density lipoprotein (LDL) percentage in iHTG and HCort-HTG dogs than HCort-NTG dogs. HCort-HTG dogs also had lower high-density lipoproteins (HDL) than HCort-NTG dogs. It was not possible to readily distinguish MSs with iHTG from MSs with HCort-HTG or Healthy-NTG using lipoprotein electrophoresis fractions. The diagnosis of iHTG remains a diagnosis by exclusion.

Angie-LAMP for diagnosis of human eosinophilic meningitis using dog as proxy: A LAMP assay for Angiostrongylus cantonensis DNA in cerebrospinal fluid.

BACKGROUND: Angiostrongylus cantonensis (rat lungworm) is recognised as the leading cause of human eosinophilic meningitis, a serious condition observed when nematode larvae migrate through the CNS. Canine Neural Angiostrongyliasis (CNA) is the analogous disease in dogs. Both humans and dogs are accidental hosts, and a rapid diagnosis is warranted. A highly sensitive PCR based assay is available but often not readily accessible in many jurisdictions. An alternative DNA amplification assay that would further improve accessibility is needed. This study aimed to assess the diagnostic utility of a newly designed LAMP assay to detect DNA of globally distributed and invasive A. cantonensis and Angiostrongylus mackerrasae, the other neurotropic Angiostrongylus species, which is native to Australia. METHODOLOGY/PRINCIPAL FINDINGS: Cerebrospinal fluid (CSF) from dogs with a presumptive diagnosis of A. cantonensis infection (2020-2022) were received for confirmatory laboratory testing and processed for DNA isolation and ultrasensitive Angiostrongylus qPCR targeting AcanR3390. A newly designed LAMP assay targeting the same gene target was directly compared to the reference ultrasensitive qPCR in a diagnostic laboratory setting to determine the presence of A. cantonensis DNA to diagnose CNA. The LAMP assay (Angie-LAMP) allowed the sensitive detection of A. cantonensis DNA from archived DNA specimens (Kappa = 0.81, 95%CI 0.69-0.92; n = 93) and rapid single-step lysis of archived CSF samples (Kappa = 0.77, 95%CI 0.59-0.94; n = 52). Only A. cantonensis DNA was detected in canine CSF samples, and co-infection with A. mackerrasae using amplicon deep sequencing (ITS-2 rDNA) was not demonstrated. Both SYD.1 and AC13 haplotypes were detected using sequencing of partial cox1. CONCLUSIONS/SIGNIFICANCE: The Angie-LAMP assay is a useful molecular tool for detecting Angiostrongylus DNA in canine CSF and performs comparably to a laboratory Angiostrongylus qPCR. Adaptation of single-step sample lysis improved potential applicability for diagnosis of angiostrongyliasis in a clinical setting for dogs and by extension, to humans.

New approach for removing co-extracted lipids before mass spectrometry measurement of persistent of organic pollutants (POPs) in foods.

Persistent organic pollutants (POPs) methods for foods and animal feeds require sufficient sample intake followed by an extensive removal of interfering matrix components and concentration before a gas chromatographic mass spectrometry (GC-MS) method can be applied. The extraction dissolves associated lipids in animal foods or feeds. Methods must eliminate all co-extracted lipids before determination by GC-MS. A new approach for removing lipids is presented using basic silica gel or metal ion immobilized silica gel (Ag+) in a single step. Absorbent order, adsorbent amounts, and flow rates were found to be essential for consistent results. KOH/silica gel or Ag+ ion (AgNO3) silica gel were both shown to retain 75-85% of the co-extracted lipids without using sulfuric acid. KOH/silica gel method applied to butter fortified at 7.3 pg TEQ/g lipid with polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) produced accurate results for all fortified congeners with 20% of predicted (n = 6). Ag+ silica gel incorporated into the Miura GO-EHT automated system produced similar results fortified at 3 pg TEQ/g lipid. During PCDD/F fortifications of butter with PCDD/Fs (n = 6), labeled standard recoveries for PCDD/Fs and planar polychlorinated biphenyls (PCBs) were all acceptable (52-99%) averaging 77% using the Miura system. A reduction in the amounts of sulfuric acid silica gel needed was possible in the completion of co-extractant removal. PCDD/F spikes into butter and for a spiked sunflower oil (PCDD/Fs and coplanar PCBs) were within ± 20% of the predicted using the Miura system; suitable for current methods criteria for foods including criteria in EU legislation.

Social Signaling and the Warrior-Big-Man among the Western Dani : A Man Called Tibenuk.

We employ the Social Signaling Model (SSM) and life history of a Western Dani big-man, Tibenuk, to analyze a neglected curiosity in the career of the big-man type. The big-man is renowned as an economic entrepreneur, the master of material displays. In New Guinea, however, big-men had invariably first gained fame and some influence as eminent warriors. The SSM accounts for this two-part career path by proposing that small-scale social organization rests on honest, competitive signaling of individual and collective fighting strength, with leaders being those who excel in these contests. The performances for which big-men are already known, conspicuous ceremonial displays, broadcast this strength indirectly. Explicitly conceptualized as symbolic fighting, they constituted indexical proxies for their sponsors' individual and collective willingness and ability to fight. Success on the battlefield, though, signaled fighting strength more directly. Men therefore had to demonstrate strength on both the battlefield and the ceremonial ground if they were to become big-men. This was Tibenuk's achievement. When he was young and at his physical peak, he demonstrated outstanding capability in war. War is a young man's game, however, and as his physical capacities waned, he shifted to politics, an older man's game, honing his political talents and developing extensive political networks that allowed him to sponsor massive pig feasts, the principal form of conspicuous ceremonial display. Tibenuk's career also reveals synergies between warrior and political talents that hitherto have been overlooked in big-man analysis.

Application of a High-Resolution Quadrupole/Orbital Trapping Mass Spectrometer Coupled to a Gas Chromatograph for the Determination of Persistent Organic Pollutants in Cow's and Human Milk.

A quadrupole/orbital trapping mass spectrometer or Q-Exactive (QE) interfaced with a gas chromatograph (GC) was optimized for measuring polychlorinated dibenzo- p-dioxins, dibenzofurans (PCDD/Fs), and polychlorinated biphenyls (PCBs) in foods. Figures of merit include (1) an instrument detection limit (IDL) for 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) of 9 femtograms (fg), (2) quantitative mass resolution from PCDD interferences (e.g., PCBs, methoxy-PCBs DDTs, polychlorodibenzylphenyl ethers, polychloroxanthenes, methyl-polychlorodibenzofuran, and polychlorodibenzothiophenes), and (3) mass accuracy <1 ppm at the IDL. The QE measured the concentrations of PCDD/Fs and PCBs in whole cow's milk with no known source of contamination (e.g., TCDD 33 fg/g fat). A National Institute of Standards and Technology (NIST) unfortified human milk standard reference material (SRM) 1953 was measured determining 27 PCDD/F and PCB congeners with an average difference of 7.6% from the certified results. The QE-GC is a benchtop instrument, easy to service, easy to operate, and requires no lock masses, mass preselection, or chemical ionization conditions. The QE-GC demonstrated that it can be an alternative to the double focusing magnetic sector instruments (sector) for the high-resolution measurement of PCDD/Fs and PCBs in dairy products.

Perspectives on Liquid Chromatography-High-Resolution Mass Spectrometry for Pesticide Screening in Foods.

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 high-resolution 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.

Determination of Multiresidue Pesticides in Botanical Dietary Supplements Using Gas Chromatography-Triple-Quadrupole Mass Spectrometry (GC-MS/MS).

A simplified sample preparation method in combination with gas chromatography-triple-quadrupole mass spectrometry (GC-MS/MS) analysis was developed and validated for the simultaneous determination of 227 pesticides in green tea, ginseng, gingko leaves, saw palmetto, spearmint, and black pepper samples. The botanical samples were hydrated with water and extracted with acetonitrile, magnesium sulfate, and sodium chloride. The acetonitrile extract was cleaned up using solid phase extraction with carbon-coated alumina/primary-secondary amine with or without C18. Recovery studies using matrix blanks fortified with pesticides at concentrations of 10, 25, 100, and 500 µg/kg resulted in average recoveries of 70-99% and relative standard deviation of 5-13% for all tested botanicals except for black pepper, for which lower recoveries of fortified pesticides were observed. Matrix-matched standard calibration curves revealed good linearity (r(2) > 0.99) across a wide concentration range (1-1000 µg/L). Nine commercially available tea and 23 ginseng samples were analyzed using this method. Results revealed 36 pesticides were detected in the 9 tea samples at concentrations of 2-3500 µg/kg and 61 pesticides were detected in the 23 ginseng samples at concentrations of 1-12500 µg/kg.

Determinations for Pesticides on Black, Green, Oolong, and White Teas by Gas Chromatography Triple-Quadrupole Mass Spectrometry.

Black, green, white, and Oolong teas, all derived from leaves of Camellia sinensis, are widely consumed throughout the world and represent a significant part of the beverages consumed by Americans. A gas chromatography-triple quadrupole-based method, previously validated for pesticides on dried botanical dietary supplements, including green tea, was used to measure pesticides fortified into black and green teas at 10, 25, 100, and 500 µg/kg. Teas from 18 vendors of tea products were then surveyed for pesticides. Of 62 black, green, white, and Oolong tea products, 31 (50%) had residues of pesticides for which no United States Environmental Protection Agency tolerances are established for tea. The following pesticides were identified on tea leaves, with concentrations between 1 and 3200 µg/kg: anthraquinone, azoxystrobin, bifenthrin, buprofesin, chlorpyrifos, cyhalothrin, cypermethrin, DDE-p,p', DDT-o,p, DDT-p,p', deltamethrin, endosulfan, fenvalerate, heptachlor, hexachlorocyclohexanes (α,ß,γ,δ), phenylphenol, pyridaben, tebuconazole, tebufenpyrad, and triazophos. DDT-p,p' was found at much higher concentrations than DDE-p,p' or DDT-o,p' in 9 of 10 teas with DDTs. A comparison between three commercially available solid-phase extraction (SPE) column brands of the same type revealed that two brands of SPE columns could be interchanged without modification of the tea method.

Multi-mycotoxin Analysis of Finished Grain and Nut Products Using Ultrahigh-Performance Liquid Chromatography and Positive Electrospray Ionization-Quadrupole Orbital Ion Trap High-Resolution Mass Spectrometry.

Ultrahigh-performance liquid chromatography using positive electrospray ionization and quadrupole orbital ion trap high-resolution mass spectrometry was evaluated for analyzing mycotoxins in finished cereal and nut products. Optimizing the orbital ion trap mass analyzer in full-scan mode using mycotoxin-fortified matrix extracts gave mass accuracies, δM, of < ± 2.0 ppm at 70,000 full width at half maximum (FWHM) mass resolution (RFWHM). The limits of quantitation were matrix- and mycotoxin-dependent, ranging from 0.02 to 11.6 µg/kg. Mean recoveries and standard deviations for mycotoxins from acetonitrile/water extraction at their relevant fortification levels were 91 ± 10, 94 ± 10, 98 ± 12, 91 ± 13, 99 ± 15, and 93 ± 17% for corn, rice, wheat, almond, peanut, and pistachio, respectively. Nineteen mycotoxins with concentrations ranging from 0.3 (aflatoxin B1 in peanut and almond) to 1175 µg/kg (fumonisin B1 in corn flour) were found in 35 of the 70 commercial grain and nut samples surveyed. Mycotoxins could be identified at δM < ± 5 ppm by identifying the precursor and product ions in full-scan MS and data-dependent MS/MS modes. This method demonstrates a new analytical approach for monitoring mycotoxins in finished grain and nut products.

Determination of mycotoxins in milk-based products and infant formula using stable isotope dilution assay and liquid chromatography tandem mass spectrometry.

A stable isotope dilution assay and liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of 12 mycotoxins, aflatoxins B1, B2, G1, G2, and M1, deoxynivalenol, fumonisins B1, B2, and B3, ochratoxin A, T-2 toxin, and zearalenone, in milk-based infant formula and foods. Samples were fortified with 12 ¹³C uniformly labeled mycotoxins ([¹³C]-mycotoxins) that correspond to the 12 target mycotoxins and prepared by dilution and filtration, followed by LC-MS/MS analysis. Quantitation was achieved using the relative response factors of [¹³C]-mycotoxins and target mycotoxins. The average recoveries in fortified milk, milk-based infant formula, milk powder, and baby yogurt of aflatoxins B1, B2, G1, and G2 (2, 10, and 50 µg/kg), aflatoxin M1 (0.5, 2.5, and 12.5 µg/kg), deoxynivalenol, fumonisins B1, B2, and B3 (40, 200, and 1000 µg/kg), ochratoxin A, T-2 toxin, and zearalenone (20, 100, and 500 µg/kg), range from 89 to 126% with RSDs of <20%. The individual recoveries in the four fortified matrices range from 72% (fumonisin B3, 20 µg/kg, milk-based infant formula) to 136% (T-2 toxin, 20 µg/kg, milk powder), with RSDs ranging from 2 to 25%. The limits of quantitation (LOQs) were from 0.01 µg/kg (aflatoxin M1) to 2 (fumonisin B1) µg/kg. Aflatoxin M1 was detected in two European Reference materials at 0.127 ± 0.013 µg/kg (certified value = 0.111 ± 0.018 µg/kg) and 0.46 ± 0.04 µg/kg (certified value = 0.44 ± 0.06 µg/kg), respectively. In 60 local market samples, aflatoxins B1 (1.14 ± 0.10 µg/kg) and B2 (0.20 ± 0.03 µg/kg) were detected in one milk powder sample. Aflatoxin M1 was detected in three imported samples (condensed milk, milk-based infant formula, and table cream), ranging from 0.10 to 0.40 µg/kg. The validated method provides sufficient selectivity, sensitivity, accuracy, and reproducibility to screen for aflatoxin M1 at nanograms per kilogram concentrations and other mycotoxins, without using standard addition or matrix-matched calibration to compensate for matrix effects.

Multi-mycotoxin analysis of finished grain and nut products using high-performance liquid chromatography-triple-quadrupole mass spectrometry.

Mycotoxins in foods have long been recognized as potential health hazards due to their toxic and carcinogenic properties. A simple and rapid method was developed to detect 26 mycotoxins (aflatoxins, ochratoxins, fumonisins, trichothecenes, and ergot alkaloids) in corn, rice, wheat, almond, peanut, and pistachio products using high-performance liquid chromatography-triple-quadrupole mass spectrometry. Test portions of homogenized grain or nut products were extracted with acetonitrile/water (85:15, v/v), followed by high-speed centrifugation and dilution with water. Mean recoveries (± standard deviations) were 84 ± 6, 89 ± 6, 97 ± 9, 87 ± 12, 104 ± 16, and 92 ± 18% from corn, rice, wheat, almond, peanut, and pistachio products, respectively, and the matrix-dependent instrument quantitation limits ranged from 0.2 to 12.8 µg/kg, depending on the mycotoxin. Matrix effects, as measured by the slope ratios of matrix-matched and solvent-only calibration curves, revealed primarily suppression and were more pronounced in nuts than in grains. The measured mycotoxin concentrations in 11 corn and wheat reference materials were not different from the certified concentrations. Nineteen mycotoxins were identified and measured in 35 of 70 commercial grain and nut products, ranging from 0.3 ± 0.1 µg/kg (aflatoxin B1 in peanuts) to 1143 ± 87 µg/kg (fumonisin B1 in corn flour). This rapid and efficient method was shown to be rugged and effective for the multiresidue analysis of mycotoxins in finished grain and nut products.

Multiresidue pesticide analysis of botanical dietary supplements using salt-out acetonitrile extraction, solid-phase extraction cleanup column, and gas chromatography-triple quadrupole mass spectrometry.

Dietary supplements form an increasing part of the American diet, yet broadly applicable multiresidue pesticide methods have not been evaluated for many of these supplements. A method for the analysis of 310 pesticides, isomers, and pesticide metabolites in dried botanical dietary supplements has been developed and validated. Sample preparation involved acetonitrile:water added to the botanical along with anhydrous magnesium sulfate and sodium chloride for extraction, followed by cleanup with solid-phase extraction using a tandem cartridge consisting of graphitized carbon black (GCB) and primary-secondary amine sorbent (PSA). Pesticides were measured by gas chromatography-tandem mass spectrometry. Accuracy and precision were evaluated through fortifications of 24 botanicals at 10, 25, 100, and 500 µg/kg. Mean pesticide recoveries and relative standard deviations (RSDs) for all botanicals were 97%, 91%, 90%, and 90% and 15%, 10%, 8%, and 6% at 10, 25, 100, and 500 µg/kg, respectively. The method was applied to 21 incurred botanicals. Quinoxyfen was measured in hops (100-620 µg/kg). Tetraconazole (48 µg/kg), tetramethrin (15 µg/kg), methamidophos (50 µg/kg), and chlorpyrifos (93 µg/kg) were measured in licorice, mallow, tea, and tribulus, respectively. Quintozene, its metabolites and contaminants (pentachloroaniline, pentachlorobenzene, pentachloroanisole, and pentachlorothioanisole and hexachlorobenzene and tecnazene, respectively), with hexachlorocyclohexanes and DDT were identified in ginseng sources along with azoxystrobin, diazinon, and dimethomorph between 0.7 and 2800 µg/kg. Validation with these botanicals demonstrated the extent of this method's applicability for screening 310 pesticides in a wide array of botanical dietary supplements.

Multiresidue pesticide analysis of dried botanical dietary supplements using an automated dispersive SPE cleanup for QuEChERS and high-performance liquid chromatography-tandem mass spectrometry.

An automated dispersive solid phase extraction (dSPE) cleanup procedure as part of the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method, coupled with liquid chromatography-tandem mass spectrometry using electrospray ionization in positive mode, was used for the simultaneous analysis of 236 pesticides in three dried powdered botanical dietary supplements (ginseng, saw palmetto, and gingko biloba). The procedure involved extraction of the dried powdered botanical samples with salt-out acetonitrile/water extraction using anhydrous magnesium sulfate and sodium chloride, followed by an automated dSPE cleanup using a mixture of octadodecyl- (C18) and primary-secondary amine (PSA)-linked silica sorbents and anhydrous MgSO4 and online LC-MS/MS analysis. Dynamic multiple-reaction monitoring (DMRM) based on the collection of two precursor-to-product ion transitions with their retention time windows was used for all of the targeted pesticides and the internal standard. Matrix-matched calibration standards were used for quantitation, and standard calibration curves showed linearity (r(2) > 0.99) across a concentration range of 0.2-400 ng/mL for the majority of the 236 pesticides evaluated in the three botanical matrices. Mean recoveries (average %RSD, n = 4) were 91 (6), 93 (4), 96 (3), and 99 (3)% for ginseng, 101 (9), 98 (6), 99 (4), and 102 (3)% for gingko biloba, and 100 (9), 98 (6), 96 (4), and 96 (3)% for saw palmetto at fortification concentrations of 25, 100, 250, and 500 µg/kg, respectively. The geometric mean matrix-dependent instrument detection limits were 0.17, 0.09, and 0.14 µg/kg on the basis of the studies of 236 pesticides tested in ginseng roots, gingko biloba leaves, and saw palmetto berries, respectively. The method was used to analyze incurred ginseng samples that contained thermally labile pesticides with a concentration range of 2-200 µg/kg, indicating different classes of pesticides are being applied to these botanicals other than the traditional pesticides that are commonly used and analyzed by gas chromatography techniques. The method demonstrates the use of an automated cleanup procedure and the LC-MS/MS detection of multiple pesticide residues in dried, powdered botanical dietary supplements.

Protocol for an electrospray ionization tandem mass spectral product ion library: development and application for identification of 240 pesticides in foods.

Modern determination techniques for pesticides must yield identification quickly with high confidence for timely enforcement of tolerances. A protocol for the collection of liquid chromatography (LC) electrospray ionization (ESI)-quadruple linear ion trap (Q-LIT) mass spectrometry (MS) library spectra was developed. Following the protocol, an enhanced product ion (EPI) library of 240 pesticides was developed by use of spectra collected from two laboratories. A LC-Q-LIT-MS workflow using scheduled multiple reaction monitoring (sMRM) survey scan, information-dependent acquisition (IDA) triggered collection of EPI spectra, and library search was developed and tested to identify the 240 target pesticides in one single LC-Q-LIT MS analysis. By use of LC retention time, one sMRM survey scan transition, and a library search, 75-87% of the 240 pesticides were identified in a single LC/MS analysis at fortified concentrations of 10 ng/g in 18 different foods. A conventional approach with LC-MS/MS using two MRM transitions produced the same identifications and comparable quantitative results with the same incurred foods as the LC-Q-LIT using EPI library search, finding 1.2-49 ng/g of either carbaryl, carbendazim, fenbuconazole, propiconazole, or pyridaben in peaches; carbendazim, imazalil, terbutryn, and thiabendazole in oranges; terbutryn in salmon; and azoxystrobin in ginseng. Incurred broccoli, cabbage, and kale were screened with the same EPI library using three LC-Q-LIT and a LC-quadruple time-of-flight (Q-TOF) instruments. The library search identified azoxystrobin, cyprodinil, fludioxinil, imidacloprid, metalaxyl, spinosyn A, D, and J, amd spirotetramat with each instrument. The approach has a broad application in LC-MS/MS type targeted screening in food analysis.

Determination of siloxanes in silicone products and potential migration to milk, formula and liquid simulants.

A pressurised solvent extraction procedure coupled with a gas chromatography-mass spectrometry-selective ion monitoring (GC-MS-SIM) method was developed to determine three cyclic siloxanes, octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6) and three linear siloxanes, octamethyltrisiloxane (L3), decamethyltetrasiloxane (L4), dodecamethylpentasiloxane (L5), in silicone products. Additionally, two different extraction methods were developed to measure these siloxanes migrating into milk, infant formula and liquid simulants (50 and 95% ethanol in water). The limits of quantification (LOQs) of the six siloxanes ranged from 6 ng/g (L3) to 15 ng/g (D6). Silicone nipples and silicone bakewares were extracted using pressurised solvent extraction (PSE) and analysed using the GC-MS-SIM method. No linear siloxanes were detected in the silicone nipple samples analysed. The three cyclic siloxanes (D4, D5 and D6) were detected in all silicone nipple samples with concentrations ranging from 0.5 to 269 µg/g. In the bakeware samples, except for L3, the other five siloxanes were detected with concentrations ranging from 0.2 µg/g (L4) to 7030 µg/g (D6). To investigate the potential migration of the six siloxanes from silicone nipples to milk and infant formula, a liquid extraction and dispersive clean-up procedure was developed for the two matrices. The procedure used a mix of hexane and ethyl acetate (1 : 1, v/v) as extraction solvent and C18 powder as the dispersive clean-up sorbent. For the liquid simulants, extraction of the siloxanes was achieved using hexane without any salting out or clean-up procedures. The recoveries of the six siloxanes from the milk, infant formula and simulants fortified at 50, 100, 200, 500 and 1000 µg/l ranged from 70 to 120% with a relative standard derivation (RSD) of less than 15% (n = 4). Migration tests were performed by exposing milk, infant formula and the liquid simulants to silicone baking sheets with known concentrations of the six siloxanes at 40°C. No siloxanes were detected in milk or infant formula after 6 h of direct contact with the silicone baking sheet plaques, indicating insignificant migration of the siloxanes to milk or infant formula. Migration tests in the two simulants lasted up to 72 h and the three cyclic siloxanes were detected in 50% ethanol after an 8-h exposure and after 2 h in 95% ethanol. The highest detected concentrations of D4, D5 and D6 were 42, 36 and 155 ng/ml, respectively, indicating very limited migration of D4, D5 or D6 into the two simulants.

Multiresidue pesticide analysis by capillary gas chromatography-mass spectrometry.

A multiresidue pesticide method using a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) procedure and capillary gas chromatography-mass spectrometry (GC-MS) is described for the determination of 166 organochlorine, organophosphorus, and pyrethroid pesticides, metabolites, and isomers in spinach. The pesticides from spinach were extracted using acetonitrile saturated with magnesium sulfate and sodium chloride, followed by solid-phase dispersive cleanup using primary-secondary amine and graphitized carbon black sorbents and toluene. Analysis is performed using different GC-MS techniques emphasizing the benefits of non-targeted acquisition and targeted screening procedures. Non-targeted data acquisition of pesticides in the spinach was demonstrated using GC coupled to a single quadrupole mass spectrometery (GC-MS) in full scan mode or multidimensional GC-time-of-flight mass spectrometery (GC × GC-TOF/MS), along with deconvolution software and libraries. Targeted screening was achieved using GC-single quadrupole mass spectrometry in selective ion monitoring (GC-MS/SIM) mode or -tandem mass spectrometry (GC-MS/MS) in multiple reaction monitoring mode. The development of these techniques demonstrates the powerful use of GC-MS for the screening, identification, and quantitation of pesticide residues in foods.

Multiresidue pesticide analysis of agricultural commodities using acetonitrile salt-out extraction, dispersive solid-phase sample clean-up, and high-performance liquid chromatography-tandem mass spectrometry.

A multiresidue method analyzing 209 pesticides in 24 agricultural commodities has been developed and validated using the original Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) procedure and high performance liquid chromatography-positive electrospray ionization-tandem mass spectrometry (LC-MS/MS) analysis. Using solvent-only calibration standards (SOCSs) and matrix-matched calibration standards (MMCSs), it was demonstrated that a minimal concentration of 5-10 µg/kg (part per billion, ppb) of analytes in matrix is required for the consistent identification of targeted pesticides with two MRM transitions. Method performance was validated by the precision and accuracy results obtained from fortification studies at 10, 25, 100, and 500 ppb and MMCSs. The method was demonstrated to achieve an average recovery of 100 ± 20% (n = 4) for >75% of evaluated pesticides at the low fortification level (10 ppb) and improved to >84% at the higher fortification concentrations in all 24 matrices. Matrix effects in LC-MS/MS analysis were studied by evaluating the slope ratios of calibration curves (1.0-100 ng/mL) obtained from the SOCSs and MMCSs. Principal component analysis (PCA) of LC-MS/MS and method validation data confirmed that each matrix exerts its specific effect during the sample preparation and LC-MS/MS analysis. The matrix effect is primarily dependent on the matrix type, pesticide type and concentration. Some caution is warranted when using matrix matched calibration curves for the quantitation of pesticides to alleviate concerns on matrix effects. The QuEChERS method with LC-MS/MS was used to identify and quantitate pesticides residues, with concentrations ranging from 2.5 to >1000 ppb in a variety of agricultural samples, demonstrating fitness for screening and surveillance applications.

Multiresidue pesticide analysis in ginseng and spinach by nontargeted and targeted screening procedures.

Five different mass spectrometers interfaced to GC or LC were evaluated for their application to targeted and nontargeted screening of pesticides in two foods, spinach and ginseng. The five MS systems were capillary GC/MS/MS, GC-high resolution time-of-flight (GC/HR-TOF)-MS, TOF-MS interfaced with a comprehensive multidimensional GC (GCxGC/TOF-MS), an MS/MS ion trap hybrid mass (qTrap) system interfaced with an ultra-performance liquid chromatograph (UPLC-qTrap), and UPLC interfaced to an orbital trap high resolution mass spectrometer (UPLC/Orbitrap HR-MS). Each MS system was tested with spinach and ginseng extracts prepared through a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure. Each matrix was fortified at 10 and 50 ng/g for spinach or 25 and 100 ng/g for ginseng with subsets of 486 pesticides, isomers, and metabolites representing most pesticide classes. HR-TOF-MS was effective in a targeted search for characteristic accurate mass ions and identified 97% of 170 pesticides in ginseng at 25 ng/g. A targeted screen of either ginseng or spinach found 94-95% of pesticides fortified for analysis at 10 ng/g with GC/MS/MS or LC/MS/MS using multiple reaction monitoring (MRM) procedures. Orbitrap-MS successfully found 89% of 177 fortified pesticides in spinach at 25 ng/g using a targeted search of accurate mass pseudomolecular ions in the positive electrospray ionization mode. A comprehensive GCxGC/TOF-MS system provided separation and identification of 342 pesticides and metabolites in a single 32 min acquisition with standards. Only 67 or 81% of the pesticides were identified in ginseng and spinach matrixes at 25 ng/g or 10 ng/g, respectively. MS/MS or qTrap-MS operated in the MRM mode produced the lowest false-negative rates, at 10 ng/g. Improvements to instrumentation, methods, and software are needed for efficient use of nontargeted screens in parallel with triple quadrupole MS.