Quantification of staphylococcal enterotoxin type A in cow milk by using a stable isotope-labelled peptide via liquid chromatography-tandem mass spectrometry.
Food Addit Contam Part A Chem Anal Control Expo Risk Assess
; 36(7): 1098-1108, 2019 Jul.
Article
em En
| MEDLINE
| ID: mdl-31094669
ABSTRACT
In this study, the staphylococcal enterotoxin type A (SEA) contaminant was quantified in cow milk by liquid chromatography-tandem mass spectrometry (LC-MS/MS) with the use of a stable isotope-labelled peptide of SEA as an internal standard. SEA was cleaned up in a two-step process that included pH control and trichloroacetic acid (TCA) precipitation. The pH control phase eliminated other proteins. TCA precipitation cleaned up SEA without special equipment. An appropriate enzyme-to-protein ratio maximised tryptic digestion. A desalting process guaranteed the stable retention of SEA-digested peptides. The coverage of amino-acid sequences (>10%) clearly identified the toxin's presence. SEA was accurately quantified using LC-MS/MS based on a multiple-reaction monitoring mode. The developed method was validated based on spiked recovery tests at 50 and 100 µg kg-1 conducted with two samples collected on a daily basis for five days based on Japanese validation guidelines. The new method exhibited good accuracy which ranged from 80% to 82%. The relative standard deviations of repeatability were 13-14% and the relative standard deviations of within-laboratory reproducibility were 13-18%. These standard deviations satisfied the criteria of the Japanese validation guidelines. The quantification limit was estimated to be 10 µg kg-1.
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Base de dados:
MEDLINE
Assunto principal:
Peptídeos
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Contaminação de Alimentos
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Leite
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Enterotoxinas
Idioma:
En
Ano de publicação:
2019
Tipo de documento:
Article