|SOFT - TIAFT 1998||Poster Session 3||Thursday October 8, 1998|
LONG TERM STABILITY OF ABUSED DRUGS AND ANTI-ABUSE CHEMOTHERAPEUTICAL AGENTS STORED AT -20°C|
David E. Moody, Kim Monti and Alan C. Spanbauer
Center for Human Toxicology, University of Utah, Salt Lake City, UT 84112, USA
|Stability is an important consideration in the use of specimens for accurate determination of analyte concentrations. To determine the long-term stability for analytes routinely analyzed by mass spectrometry in this laboratory, quality control (QC) results were plotted versus time. The time required for the initial concentration to reach a specified level of deviation (i.e. 10%) was then determined from the slopes. QCs were prepared at 3 concentrations in drug-free matrix and stored at approximately -20°C; urines were fortified with 2% sodium fluoride; plasmas (except for those containing cocaine) were prepared with heparin; those used for cocaine and metabolites were fortified with sodium flouride and potassium citrate. Data are summarized below for the low concentration QCs.|
Both positive and negative slopes were found. With the exception of EDDP concentrations were within 10% of initial for at least one year, and in many cases, several years.