Stability of methylecgonidine and ecgonidine in sheep plasma in vitro

Background: Crack smokers are exposed to a pyrolysis product, methylecgonid ine (MEG), which can be used as an analytical marker for crack smoking. Ecg onidine (EC), a hydrolytic product of MEG, has been identified in urine of crack smokers. MEG undergoes conversion to EC, complicating analysis and pe rhaps explaining a lack of forensic blood specimens containing MEG. Methods: We developed gas chromatography-mass spectrometry (GC-MS) assays f or MEG and EC. Plasma was collected from sheep blood containing 0, 0.06, or 0.24 mol/L (0%, 0.25%, or 1%) NaF. MEG was added to these plasmas, and the y were incubated at -80, 1, 21, or 37 degreesC to determine whether there w ere temporal, temperature, or storage effects on MEG stability over 48 h. Results: Decreased temperature and increased NaF concentrations limited MEG degradation and EC formation. MEG stored in plasma at -80 degreesC was sta ble up to 1 month, even in the absence of NaF. Conclusions: MEG is stable in sheep plasma collected in commercially availa ble, evacuated blood-collection tubes containing NaF and stored at -80 degr eesC In vitro formation of EC can be minimized with appropriate sample hand ling, and its in vivo formation may provide a better marker of crack smokin g than its parent pyrolysis product. (C) 2000 American Association for Clin ical Chemistry.