Certification of Ochratoxin A Reference Materials: Calibration Solutions OTAN-1 and OTAL-1 and a Mycotoxin-Contaminated Rye Flour MYCO-1

Bates, Jennifer; Bahadoor, Adilah; Cui, Yi; Meija, Juris; Windust, Anthony

doi:10.5740/jaoacint.19-0086

Cited by 6 publications

(15 citation statements)

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“…S36–S39). Although the reported certified concentration for OTAL-1 was obtained by qHNMR, without backup data from qH{ 13 C}NMR, these results would bear less confidence. As such, the 13 C 6 -ochratoxin A case study underscored the importance of 13 C-decoupling methods when quantifying tautomeric compounds and as a simplifying tool in the analysis and measurement of 13 C-labeled compounds.…”

Section: Resultsmentioning

confidence: 98%

“…Certified reference materials of isotopically labeled compounds provide a reliable means to produce accurate measurements when used as internal standards . To produce an isotopically labeled certified reference material for 13 C 6 -ochratoxin A (OTAL-1), its absolute concentration was certified by qHNMR using maleic acid as the external standard .…”

Section: Resultsmentioning

confidence: 99%

“…Multiple tautomers of ochratoxin A have been documented. , Our NMR experiments corroborated these reports and at the same time showed that tautomerization was minimized with CD 3 OD as a solvent rather than CD 3 CN + 0.1% DCOOH (Supporting Information Figure S21). Bound by the unsurmountable requirement of preparing the OTAL-1-certified reference material, the only NMR solvent that could be used for the qNMR measurement of 13 C 6 -ochratoxin A was CD 3 CN + 0.1% DCOOH . To make it work, rigorous monitoring first established that the tautomerization of 13 C 6 -ochratoxin A in CD 3 CN + 0.1% DCOOH did not lead to unwanted decomposition pathways (Supporting Information Figure S22).…”

Section: Resultsmentioning

confidence: 99%

“…An ANOVA comparison confirmed that both produced statistically similar data (Table 2 and Supporting Information pg. 35). As such, this example validates yet another versatile aspect of 13 C-decoupling methods for small molecules.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Certified reference materials of isotopically labeled compounds provide a reliable means to produce accurate measurements when used as internal standards. 35 To produce an isotopically labeled certified reference material for 13 C 6 -ochratoxin A (OTAL-1), its absolute concentration was certified by qHNMR using maleic acid as the external standard. 35 However, preliminary NMR studies on the 13 C 6 -ochratoxin A material used to produce OTAL-1 had revealed that the material was tautomerizing in solution, due to a limited amount of material, the NMR sample would be dilute enough that 13 C-satellites were not likely to be visible, and lastly the 1 H− 13 C signal for H (16−20) was very broad to potentially mask impurities and/or tautomers along its broad span (Figure 4).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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¹³C-Satellite Decoupling Strategies for Improving Accuracy in Quantitative Nuclear Magnetic Resonance

Bahadoor

Brinkmann

2020

Anal. Chem.

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Quantitative 1 H nuclear magnetic resonance (qHNMR) with an appropriate internal standard is a wellestablished quantitation method for assigning purity to organic molecules. For accurate measurements, the premise of qHNMR relies on the careful selection of integrals, for both the analyte and the standard, in such a way that the selected integrals are free from interferences. The 13 C-satellite signals of adjacent integrals, low-level impurities, and tautomer signals are among the common integral interferences that are typically encountered. One of the simplest ways to identify and avoid these interferences is to decouple the 13 Csatellites. Two decoupling schemes were explored to illustrate the benefits of 13 C-decoupling for qHNMR or qH{ 13 C}NMR: GARP and bilevel adiabatic broadband decoupling. Unwanted sample heating and nuclear Overhauser effect (NOE) enhancements are the two main drawbacks of decoupling schemes. We show that with careful optimization of acquisition parameters and decoupling power, no excessive sample heating occurred during acquisition at 400 MHz. At 900 MHz, only bilevel adiabatic decoupling could be safely implemented. Furthermore, any undesirable NOE enhancements were completely avoided if acquisition was executed with an inverse-gated pulse sequence. We explored and confirmed the benefits of qH{ 13 C}NMR through the quantitation of a diverse set of compounds, namely, small molecules (dimethyl terephthalate and zearalenone), a 13 C-labeled compound ( 13 C 6 -ochratoxin A), and an octapeptide (angiotensin II). Statistical comparisons confirmed that qH{ 13 C}NMR produced comparable data to qHNMR. However, with qH{ 13 C}NMR data providing added clarity about the presence of overlapping 13 C-satellites, impurities, and tautomers, it has an edge over qHNMR for accurate measurements. 13 C-decoupled proton spectra have become a routine. By far, the most commonly employed pulse sequence to decouple 13 C-satellites is GARP (globally optimized alternating phase rectangular pulses). 2−7 We have employed GARP-mediated 13

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

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¹³C-Satellite Decoupling Strategies for Improving Accuracy in Quantitative Nuclear Magnetic Resonance

Bahadoor

Brinkmann

2020

Anal. Chem.

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Production and certification of BOTS-1: bovine muscle–certified reference material for incurred veterinary drug residues

et al. 2023

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A freeze-dried bovine muscle–certified reference material (CRM), known as BOTS-1 (DOI: https://doi.org/10.4224/crm.2018.bots-1), containing incurred residues of commonly used veterinary drugs was produced and certified for the mass fraction of eight veterinary drug residues. Value assignment was carried out using liquid chromatography tandem mass spectrometry (LC–MS/MS) methods in conjunction with isotope dilution and standard addition approaches involving stable isotope internal standards. Data from the National Research Council of Canada (NRC), Canadian Food Inspection Agency (CFIA), United States Department of Agriculture (USDA), and the Federal Office of Consumer Protection and Food Safety in Germany (BVL) were used for value assignment. Results for two drug residues were also obtained through an international inter-laboratory comparison CCQM-K141/P178 organized under the auspices of the International Bureau of Weights and Measures (BIPM). Quantitative NMR (1H-qNMR) was used to characterize primary standards of all veterinary drugs certified. The certified mass fractions of the veterinary drug residues were 490 ± 100 µg/kg for chlorpromazine, 44 ± 4.4 µg/kg for ciprofloxacin, 3.3 ± 1.4 µg/kg for clenbuterol, 9.5 ± 0.8 µg/kg for dexamethasone, 57 ± 4.8 µg/kg for enrofloxacin, 3.0 ± 0.4 µg/kg for meloxicam, 12.4 ± 1.2 µg/kg for ractopamine, and 2290 ± 120 µg/kg for sulfadiazine with expanded uncertainties quoted (95% confidence) which include the effects due to between-bottle inhomogeneity, instability during long-term storage and transportation, and characterization.

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Comparison of calibration strategies for accurate quantitation by isotope dilution mass spectrometry: a case study of ochratoxin A in flour

Bates,

Bahadoor,

Tittlemier

et al. 2023

Anal Bioanal Chem

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Analysis of low-level organic contaminants in complex matrices is essential for monitoring global food safety. However, balancing sample throughput with complex experimental designs and/or sample clean-up to best reduce matrix effects is a constant challenge. Multiple strategies exist to mitigate these effects, with internal standard-based methods such as isotope dilution mass spectrometry (IDMS) being the most advantageous. Here, multiple internal calibration strategies were investigated for the quantification of ochratoxin A (OTA) in wheat samples by liquid chromatography-mass spectrometry (LC-MS). Internal standard-based quantitation methods such as single (ID1MS), double (ID2MS), and quintuple (ID5MS) isotope dilution mass spectrometry, as well as external standard calibration, were explored and compared. A certified reference material (CRM) of OTA in flour, MYCO-1, was used to evaluate the accuracy of each method. External calibration generated results 18–38% lower than the certified value for MYCO-1, largely due to matrix suppression effects. Concurrently, consistently lower OTA mass fractions were obtained for the wheat samples upon quantitation by external calibration as opposed to ID1MS, ID2MS, and ID5MS. All isotope dilution methods produced results that fell within the expected range for MYCO-1 (3.17–4.93 µg/kg), validating their accuracy. However, an average 6% decrease in the OTA mass fraction was observed from results obtained by ID1MS compared to those by ID2MS and ID5MS. Upon scrutiny, these differences were attributed to an isotopic enrichment bias in the isotopically labelled internal standard [13C6]-OTA that was used for ID1MS, the OTAL-1 CRM. The advantages and limitations of each isotopic method are illustrated.

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Certification of Ochratoxin A Reference Materials: Calibration Solutions OTAN-1 and OTAL-1 and a Mycotoxin-Contaminated Rye Flour MYCO-1

Cited by 6 publications

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¹³C-Satellite Decoupling Strategies for Improving Accuracy in Quantitative Nuclear Magnetic Resonance

¹³C-Satellite Decoupling Strategies for Improving Accuracy in Quantitative Nuclear Magnetic Resonance

Production and certification of BOTS-1: bovine muscle–certified reference material for incurred veterinary drug residues

Comparison of calibration strategies for accurate quantitation by isotope dilution mass spectrometry: a case study of ochratoxin A in flour

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Certification of Ochratoxin A Reference Materials: Calibration Solutions OTAN-1 and OTAL-1 and a Mycotoxin-Contaminated Rye Flour MYCO-1

Cited by 6 publications

References 0 publications

13C-Satellite Decoupling Strategies for Improving Accuracy in Quantitative Nuclear Magnetic Resonance

13C-Satellite Decoupling Strategies for Improving Accuracy in Quantitative Nuclear Magnetic Resonance

Production and certification of BOTS-1: bovine muscle–certified reference material for incurred veterinary drug residues

Comparison of calibration strategies for accurate quantitation by isotope dilution mass spectrometry: a case study of ochratoxin A in flour

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Product

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About

¹³C-Satellite Decoupling Strategies for Improving Accuracy in Quantitative Nuclear Magnetic Resonance

¹³C-Satellite Decoupling Strategies for Improving Accuracy in Quantitative Nuclear Magnetic Resonance