Reference materials for analytical toxicology including doping control: freeze-dried urine samples.

Area of Science:

• Forensic Toxicology
• Analytical Chemistry
• Biochemistry

Background:

• Accurate detection of doping agents is crucial for sports integrity.
• Standardized reference materials are essential for reliable intercomparison exercises in doping control.

Purpose of the Study:

• To evaluate the feasibility of using freeze-dried urine samples as reference materials for doping agent analysis.
• To assess the stability and integrity of various doping agents in freeze-dried urine over time.

Main Methods:

• Preparation of urine samples fortified with specific doping agents (caffeine, ephedrines, amphetamines, steroids).
• Lyophilization of prepared urine samples.
• Stability assessment of freeze-dried samples stored at 4-8°C for up to 18 months.
• Comparison of analyte concentrations between freeze-dried and frozen (-80°C) samples.

Main Results:

• Freeze-dried urine samples demonstrated good feasibility as reference materials.
• Minimal analyte loss (<5%) was observed for most compounds, except for amphetamine (up to 18%) and norpseudoephedrine (up to 10%).
• Observed analyte losses were attributed to volatility during the lyophilization process and remained constant over 18 months.
• A slight increase in pH was noted upon reconstitution of samples.

Conclusions:

• Freeze-dried urine samples are a viable option for reference materials in doping control.
• The stability of most doping agents in freeze-dried urine is adequate for intercomparison exercises.
• Volatile compounds require careful consideration due to potential losses during lyophilization.