title: Detection and quantification of ricin in beverages using isotope dilution tandem mass spectrometry.
abstract: The toxic plant protein ricin has gained notoriety due to wide availability and potential use as a bioterrorism agent, with particular concern for food supply contamination. We have developed a sensitive and selective mass spectrometry-based method to detect ricin in tap water, 2% milk, apple juice, and orange juice. Ricin added to beverage matrices was extracted using antibody-bound magnetic beads and digested with trypsin. Absolute quantification was performed using isotope dilution mass spectrometry with a linear ion trap operating in product-ion-monitoring mode. The method allows for identification of ricin A chain and B chain and for distinction of ricin from ricin agglutinin within a single analytical run. Ricin-bound beads were also tested for deadenylase activity by incubation with a synthetic ssDNA oligomer. Depurination of the substrate by ricin was confirmed by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOFMS). This method was used successfully to extract ricin from each beverage matrix. The activity of recovered ricin was assessed, and quantification was achieved, with a limit of detection of 10 fmol/mL (0.64 ng/mL).
authors.affiliation: Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, 4770 Buford Highway, Atlanta, Georgia 30341, USA.
authors.forename: Sara C
authors.initials: SC
authors.lastname: McGrath
authors.forename: David M
authors.initials: DM
authors.lastname: Schieltz
authors.forename: Lisa G
authors.initials: LG
authors.lastname: McWilliams
authors.forename: James L
authors.initials: JL
authors.lastname: Pirkle
authors.forename: John R
authors.initials: JR
authors.lastname: Barr
mesh_terms: D001628:Beverages / Q000032:analysis*; D006801:Humans; D007553:Isotope Labeling / Q000379:methods*; D012276:Ricin / Q000032:analysis*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D012276:Ricin