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1.
J AOAC Int ; 97(3): 946-55, 2014.
Article in English | MEDLINE | ID: mdl-25051649

ABSTRACT

An analytical method to speciate two inorganic As forms [arsenite, As(lll) and arsenate, As(V)] in indica and japonica types of rice (both husked and polished) and determine the inorganic As concentration as the sum of these two was internationally validated. The method can additionally determine two organic As compounds, monomethylarsonic acid and dimethylarsinic acid, in rice as separate LC peaks. The method is based on LC separation and inductively coupled plasma (ICP)-MS detection. The method was evaluated through the International Union of Pure and Applied Chemistry/lnternational Organization for Standardization/AOAC harmonized protocol. Sixteen laboratories from four countries participated in the study, and 13 laboratories returned valid data. Twenty test portions of 10 blind duplicates of indica and japonica type rice samples (both husked and polished) were used in this study. Repeatability RSD (RSDr) and reproducibility RSD (RSDR) were calculated at five concentrations of total inorganic As between 0.03 and 0.68 mg/kg. The RSDr was in a range of 3.8 to 7.7% and the RSDR was in a range of 10 to 36%. These performance characteristics were found to be sufficient for determination of inorganic As at or higher than 0.03 mg/kg. Applicability of the method was estimated to be in a range of 0.02-2.0 mg/kg.


Subject(s)
Arsenates/analysis , Arsenites/analysis , Chromatography, Liquid/methods , Mass Spectrometry/methods , Oryza/chemistry , Cooperative Behavior , Limit of Detection , Spectrophotometry, Atomic
2.
Rapid Commun Mass Spectrom ; 16(24): 2387-93, 2002.
Article in English | MEDLINE | ID: mdl-12478585

ABSTRACT

Negative-ion fast-atom bombardment collision-induced dissociation tandem mass spectrometric (FAB-CID-MS/MS) methodology was successfully applied to verify the highly complex structure of ostreocin-D (MW 2633), a new palytoxin analog isolated from the marine dinoflagellate Ostreopsis siamensis and proposed to be 42-hydroxy-3,26-didemethyl-19,44-dideoxypalytoxin based on NMR data. The charge-remote fragmentations were facilitated by a negative charge introduced to a terminal amino group or to a hydroxyl group at the other terminus by a reaction with 2-sulfobenzoic acid cyclic anhydride. Product ions generated from the [M - H](-) ions provided information on the structural details of ostreocin-D. Comparisons between the spectral data for ostreocin-D and palytoxin also provided a rational basis for the assignments of product ions.


Subject(s)
Bridged Bicyclo Compounds, Heterocyclic/chemistry , Dinoflagellida/chemistry , Pyrans/chemistry , Spectrometry, Mass, Fast Atom Bombardment/methods , Acrylamides/chemistry , Animals , Bridged Bicyclo Compounds, Heterocyclic/isolation & purification , Cnidarian Venoms , Ions , Marine Toxins/chemistry , Molecular Structure , Pyrans/isolation & purification
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