title: Absolute Quantification of Lipophilic Shellfish Toxins by Quantitative Nuclear Magnetic Resonance Using Removable Internal Reference Substance with SI Traceability.
abstract: Okadaic acid (OA), a lipophilic shellfish toxin, was accurately quantified using quantitative nuclear magnetic resonance with internal standards for the development of an authentic reference standard. Pyridine and the residual proton in methanol-d4 were used as removable internal standards to limit any contamination. They were calibrated based on a maleic acid certified reference material. Thus, the concentration of OA was traceable to the SI units through accurate quantitative NMR with an internal reference substance. Signals from the protons on the oxygenated and unsaturated carbons of OA were used for quantification. A reasonable accuracy was obtained by integrating between the lower and upper (13)C satellite signal range when more than 4 mg of OA was used. The best-determined purity was 97.4% (0.16% RSD) when 20 mg of OA was used. Dinophysistoxin-1, a methylated analog of OA having an almost identical spectrum, was also quantified by using the same methodology.
authors.affiliation: Japan Food Research Laboratories, Tama Laboratory.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kato
authors.forename: Maki
authors.initials: M
authors.lastname: Saito
authors.forename: Mika
authors.initials: M
authors.lastname: Nagae
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Fujita
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Watai
authors.forename: Tomoji
authors.initials: T
authors.lastname: Igarashi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yasumoto
authors.forename: Minoru
authors.initials: M
authors.lastname: Inagaki
mesh_terms: D002138:Calibration; D004141:Dinoflagellida / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008387:Marine Toxins / Q000032:analysis*; D019319:Okadaic Acid / Q000032:analysis* / Q000031:analogs & derivatives; D011714:Pyrans / Q000032:analysis*; D012015:Reference Standards; D012680:Sensitivity and Specificity; D012758:Shellfish / Q000032:analysis*
chemical_list: D008387:Marine Toxins; D011714:Pyrans; D019319:Okadaic Acid; C051904:dinophysistoxin 1