Author(s): Dan Li; Justin A. Steimling; Joseph D. Konschnik, Scott L. Grossman; Ty W. Kahler
Published By: Journal of AOAC International
Year of Publication: 2019
Abstract: Background: Mycotoxins are big concerns in food safety. Analytical methods are important for the evaluation of mycotoxins in different food commodities. Objective: In this study, stable isotope dilution assay (SIDA) was compared with a matrix-matched calibration method for the quantification of mycotoxins in four different commercially available commodities and two reference materials. Methods: All samples were extracted with water–acetonitrile (50+50, v/v), followed by filtration and LC–tandem MS analysis. Results: SIDA calibration accuracies ranged from 78.6 to 112% with relative SDs (RSDs) ≤16% across all four matrices. The majority of the recoveries across all matrices ranged from 70 to 120% with RSDs <11%. Of the four mycotoxins in the reference materials analyzed, only three had 13C-internal standard (IS), whereas the fourth was quantified using a closely eluting 13C-IS for a different mycotoxin. Mycotoxins paired with their corresponding 13C-IS had accuracies >90%, whereas accuracies for the mismatched mycotoxin/13C-IS were <14%. Conclusions: When 13C-IS are not available, matrix-matched calibration was also evaluated as an alternative to quantitating target mycotoxins. The use of 13C-IS is the best way to dynamically account for prevalent matrix effects, but matrix matching provides a viable alternative. Highlights: The study compared SIDA and matrix-matched calibration methods in terms of recovery, efficiency, advantages, and limitations for LC-MS based mycotoxin analysis
Author(s): Sharon Lupo
Published By: LCGC North America
Issue: Volume 36, Issue 9
Year of Publication: 2018
Abstract: Liquid chromatography–mass spectrometry (LC–MS) has become the preferred analytical technique for many challenging assays based on its selectivity, sensitivity, and broad applicability to compounds of varying polarity. Despite the advantages of the technique, the complexity of LC–MS systems often leaves analysts struggling to meet method detection limits. In this installment of “Column Watch,” several strategies are discussed to improve method sensitivity through the reduction of contaminants, the careful selection of LC method conditions, and the optimization
of MS interface settings. By understanding the relationship between these parameters and ionization efficiency, analysts can enhance their signal-to-noise ratio and realize the hidden potential of the LC–MS technique.
Author: James Watterson
Published By: SelectScience
Year of Publication: 2016
Dr. James Watterson, Associate Professor, Department of Forensic Science at Laurentian University in Ontario, told SelectScience about his forensic toxicology research and the technologies he utilizes in his work. Dr. Watterson’s primary interest is the characterization of drug and metabolite disposition in skeletal remains, and he has employed a variety of chromatography and mass spectrometry-based analyses. The team is now investigating the probative power of quantitative drug-metabolite relationships in bone using LC-MS techniques, which offer greater sensitivity and selectivity for analyses of a number of different metabolites. As Dr. Watterson explains, “Now that we have switched to UPLC-qTOF-MS as our primary analytical approach, the advantages are absolute: substantially reduced sample preparation requirements, vastly improved sensitivity and selectivity, and a much greater of analytes that may be assayed.” The choice of LC column for such analyses is also of critical importance, the correct column chemistry is essential for efficient separation. For example, the team used Raptor Biphenyl columns, with long column geometry and small particle/fused-core stationary phase, to maximize resolution of polar metabolites of phenothiazine drugs, using UPLC-PDA. This approach was critical in the characterization of these metabolites and of the phenothiazine oxidation products, which are produced during sample preparation. Dr. Watterson comments that, “the biphenyl column has been very helpful in resolving those compounds too, as we applied this method to UPLC-qTOF-MS.” Dr. Watterson advises choosing reagents and columns carefully, as background impurities are much more visible using current technologies.