Method for the determination of thyreostats in milk samples using LC-MS/MS

Area of Science:

• Analytical Chemistry
• Food Safety Analysis
• Veterinary Pharmacology

Background:

• Thyreostats are used in veterinary medicine but can contaminate milk.
• Accurate detection methods are crucial for ensuring milk product safety and regulatory compliance.
• Existing methods may lack the sensitivity or selectivity required for trace-level detection in complex matrices.

Purpose of the Study:

• To develop and validate a highly sensitive and selective analytical method for determining four specific thyreostats in various milk types.
• To establish a reliable method for monitoring thyreostat residues in cow's, lamb's, and goat's milk.
• To ensure compliance with stringent European Union regulatory criteria (2002/657/EC).

Main Methods:

• Milk protein precipitation using acetonitrile.
• Derivatization of thyreostats with 3-iodobenzylbromide.
• Liquid-liquid extraction with ethyl acetate for matrix separation.
• Analysis via Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) in positive electrospray ionization mode.

Main Results:

• The developed LC-MS/MS method demonstrated high sensitivity for all four target thyreostats.
• Decision limits (CCα) were below 1 ng/mL for all analytes.
• Detection capabilities (CCβ) were below 1.5 ng/mL for all analytes.
• Analyte stability in sample extracts under various storage conditions was successfully evaluated.

Conclusions:

• The validated analytical method is suitable for the sensitive and selective determination of thyreostats in cow's, lamb's, and goat's milk.
• The method meets the rigorous validation requirements set by 2002/657/EC.
• This method provides a reliable tool for food safety authorities to monitor thyreostat residues in milk products.