In vitro stability of cocaine in whole blood and plasma including ecgonineas a target analyte

The in vitro stability of cocaine (COC) was monitored in fresh whole blood and plasma stabilized with potassium fluoride (0.25%) for as long as 15 day s. The samples were stored at 4 degreesC, 20 degreesC and 40 degreesC. Addi tionally, fresh plasma samples containing either benzoylecgonine (BZE), ecg onine methyl ester (EME) or ecgonine (ECG) were stored at 4 degreesC and 20 degreesC. Data were established using subsequent solid-phase extraction pr ocedures and high-performance liquid chromatography coupled to atmospheric pressure ionization mass spectrometry for isolation and quantitation of COC , BZE, EME, and ECG. COG, BZE, and EME concentrations decreased with increasing storage temperat ure and time after an apparent first-order reaction kinetic. Only ECG appea red to be stable at storage temperatures as high as 20 degreesC for the ent ire observation period. At 40 degreesC, the amount of ECG produced from hyd rolysis of COC still totalled 80% of the initial COC concentration. Hydroly sis of COC to EME occurred more rapidly in plasma than in blood. The dynami c degradation profiles obtained were dependent on the storage temperature. The conversion of COC to BZE, EME, and ECG appeared to be stoichiometric at all time intervals at storage temperatures of 4 degreesC and 20 degreesC. The presence of any hydrolysis product of COC in blood or plasma constitute s confirmatory evidence of COC incorporation, and determination of ECG seem s most promising even in samples stored under unfavorable conditions.