Internal quality control samples for hair testing.

Area of Science:

• Forensic Toxicology
• Analytical Chemistry

Background:

• Authentic hair samples for multi-analyte drug testing are often unavailable as reference material.
• Quality assurance is crucial for accurate detection of chronic drug use and single-dose intake via hair analysis.

Purpose of the Study:

• To investigate the efficacy of a soaking technique using drug-free hair as a substitute for quality assurance in hair testing.
• To evaluate the incorporation, retention, and stability of 29 common pharmaceuticals and drugs of abuse in soaked hair samples.

Main Methods:

• Drug-free hair samples were exposed to reference standard solutions of 29 drugs for several hours.
• Incorporation amounts were quantified before and after standard washing procedures.
• Homogeneity, method imprecision, and stability of soaked samples were assessed over a one-year period.

Main Results:

• Incorporated drug amounts ranged from 0.27-4.5 ng/mg (unwashed) after 1-hour exposure.
• 27%-70% of incorporated drugs remained after washing, indicating penetration into hair cells.
• Soaked samples showed good homogeneity and method imprecision (<20% at low level, <17% at high level) over one year, with chlordiazepoxide and zopiclone being exceptions.

Conclusions:

• Soaked hair samples are suitable substitutes for quality assurance in multi-analyte hair testing when authentic samples are unavailable.
• The soaking technique facilitates drug incorporation and retention, mimicking natural drug uptake.
• Prepared hair samples offer reliable quality control for up to a year, with noted instability for specific analytes.