Comparison of immunoaffinity chromatography combined with gas chromatography-negative ion chemical ionisation mass spectrometry and radioimmunoassay for screening dexamethasone in equine urine.

This study compares the effectiveness of two analytical methods – radioimmunoassay and immunoaffinity chromatography combined with gas chromatography-negative ion chemical ionisation mass spectrometry – for detecting dexamethasone in horse urine after the administration of the drug.

Methodologies Used

The research employed two distinct analytical methods:

• Radioimmunoassay (RIA): This is a sensitive in vitro assay technique used to measure concentrations of substances such as peptides, hormones, and drugs in biological samples.
• Immunoaffinity Chromatography (IAC) Combined with Gas Chromatography-Negative Ion Chemical Ionisation Mass Spectrometry: Immunoaffinity chromatography is a type of chromatography that utilizes the specific binding between an antigen and an antibody to separate these molecules from a mixture. The IAC is then coupled with Gas Chromatography-Negative Ion Chemical Ionisation Mass Spectrometry. The latter represents a special type of mass spectrometry that is highly selective and sensitive, making it particularly useful for the detection of specific substances.

Subject and Approach

The study used urine samples collected from a mare over a period of 144 hours after a 26 mg dose of dexamethasone sodium phosphate was administered. Dexamethasone is a potent anti-inflammatory and immunosuppressant, and its presence in sport horses can indicate unethical performance enhancement, equating doping in human sports.

Objective of Comparison

The object of the comparison was to determine which method:

• Was more sensitive in detecting the presence of dexamethasone.
• Provided more reliable results for the screening of dexamethasone in equine post-race urine.

The study hence contributes to the evolving practices and technologies used for fair and accurate drug testing in equestrian sports, providing crucial insight into the respective advantages of RIA and IAC methods in this context.