Determination and stability of some international screening limited drugs in equine blood by LC-MS/MS

Stability of some international screening limited therapeutic substances for doping control in equine blood has been investigated with a validated method by using LC-MS/MS after chemical hydrolysis with orthophosphoric acid. Whole blood samples were extracted with a WAX cartridge on auto-SPE. Stability test of the drug substances performed at the same time in working solution and matrix at +4 degrees C, -20 degrees C, +20 degrees C in dark and +20 degrees C in light conditions for 1, 2, 3 and 4 weeks. For short-time stability, the effects of 6 h storage at +55 degrees C was also investigated. Repeated data were statistically analyzed with ANOVA. All substances in working solution were stable at -20 degrees C and +4 degrees C. In the blood matrix, higher temperatures (+20 degrees C) in light and dark caused degradation of substances at the end of four weeks and short-term study (P