Detection and Quantification of Ricin in Beverages Using Isotope Dilution Tandem Mass Spectrometry

• Published in: Analytical chemistry (Washington) Vol. 83; no. 8; pp. 2897 - 2905
• Main Authors: McGrath, Sara C, Schieltz, David M, McWilliams, Lisa G, Pirkle, James L, Barr, John R
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.04.2011
• Subjects: Analytical chemistry; Beverages; Beverages - analysis; Chemistry; Exact sciences and technology; Food contamination & poisoning; Humans; Isotope Labeling - methods; Isotopes; Mass spectrometry; Proteins; Ricin - analysis; Spectrometric and optical methods; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Identification; Matrix assisted laser desorption ionization; Oligomer; Ion trap; Plant; Sample preparation; Castor (seed); Detection limit; Beverage; Monitoring; Quantitative analysis; Milk; Vegetals; Antibody; Isotope dilution; Foodstuff; Tap water; Contamination; Protein; Substrate; Apple; Time of flight method; Mass spectrometry MS/MS; Simultaneous measurement; Mass spectrometry
• DOI: 10.1021/ac102571f
• ISSN: 0003-2700

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).