Analysis of dexamethasone and betamethasone in bovine urine by purifbation with an "on-line" immunoaffinity chromatography-high-performance liquid chromatography system and determination by gas chromatography-mass spectrometry

Rezo Bagnati, Vittorio Ramazza, Maurizio Zucchi, Anselmo Simonella, Flora Leone, Alberto Bellini, Roberto Fanelli

Research output: Contribution to journalArticle

Abstract

A method, for the immunoaffinity extraction of dexamethasone and betamethasone in bovine urine, followed by high-pressure liquid chromatography (HPLC) fractionation and gas chromatography-mass spectrometry determination, is described. A commercial immunoaffinity gel, containing antibodies raised against dexamethasone, was used to prepare an immunoaffinity cartridge which was inserted in an automatic HPLC system for on-line extraction and purification. By injecting urine samples (spiked with flumethasone as internal standard) directly into the system, it was possible to collect purified fractions, containing the analytes of interest. The fractions were dried and derivatized to yield the tetra-trimethylsilyl derivatives of the three corticosteroids, which were analyzed by selected ion monitoring gas chromatography-mass spectrometry. The method allowed a very good purification of samples and reached a detection limit of 0.1 ng/ml for dexamethasone and 0.2 ng/ml for betamethasone. Several samples, coming from a steer treated with dexamethasone and from other bovines coming from breedings in northern Italy, were analyzed with the method described. Dexamethasone levels ranged from 0.12 to 146 ng/ml.

Original languageEnglish
Pages (from-to)119-126
Number of pages8
JournalAnalytical Biochemistry
Volume235
Issue number2
DOIs
Publication statusPublished - Mar 15 1996

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology

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