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Low‐cost isotope dilution made easy: An alternate reaction of an analyte in a matrix and in a standard solution with isotope‐labeled or unlabeled derivatizing reagents allows quantification of zearalenone in maize flour without the need for a calibration curve. This is possible by direct calculation of the relative response factor for the analyte/internal standard ratio of the sample (see picture).

Zearalenone is a mycotoxin mainly produced by severalFusarium species, which are known to colonize grains in temperate climates. The purpose of the study is to provide a reliable isotope dilution method for the quantification of this mycotoxin. A derivative of the analyte to be used as standard is obtained by reaction with acetic anhydride, which is available in two pure isotopic forms, a protonated ("light") and a hexadeuterated ("heavy"). The derivatized standards are added to the matrix split intwo parts. Then, the derivatization procedure is repeated on both matrices derivatizing the part containing the "heavy" labelled standard with the "light" acetic anhydride and the part containing the "light" labelled standard with the "heavy" acetic anhydride. Both extracted mixtures are analyzed by LC/MS, monitoring the "light" and the "heavy" labelled analytes and using the former as standard for the latter in one case and viceversa in the other case. The method allowed to obtain very good results, without the need of IAC purification.

Die preiswerte Isotopenverdünnung leicht gemacht: Über die Reaktion eines Analyten in einer Matrix und in einer Standardlösung mit isotopenmarkierten oder nichtmarkierten Derivatisierungsreagentien gelingt die Quantifizierung von Zearalenon in Maismehl, ohne dass eine Kalibrierungskurve erforderlich ist. Dazu wird der relative Antwortfaktor für das Verhältnis Analyt/interner Standard der Probe berechnet (siehe Bild).