摘要：This study aims to analyze changes in appearance, weight and purity of 31 samples of cocaine seizes whose sanctioning procedure is carried out by the judicial authority. The Corps seized these samples in the Autonomous Community of Castilla y León, and they were analyzed by the laboratory of Health and Social Policy Area of the Sub-delegation of Government in Valladolid for 60 months. Samples were stored under two conditions of temperature and humidity, the environmental environment "E" 22.30 °C /- 2.88 °C and 65.96 % /- 1.72 % of relative humidity and refrigerated environment "R" 4.64 °C /- 0.44 °C and 28.36 /- 0.76 % of relative humidity. Results show there is a decrease in purity in the samples over time. The percentage change (ΔC) for environmental samples in the first 9 months was ΔC9 = -17.53 %, at 12 months ΔC12= -27.33 %, at 36 months ΔC36= -28.19 % and at 60 months ΔC60= -28.95 % on average. In the case of the refrigerated samples, the percentage change after 9 months was ΔC9 = -15.93 at 12 months ΔC12= -18.51, at 36 months ΔC36= -19.25 and at 60 months ΔC60= -20.09. The negative value of ΔC indicates purity loss. The influence of the temperature and humidity influence, at the loss weight average percentage in the samples under ambient conditions -10.94 % ( /- 4.21 %) was bigger than loss weight average percentage in the specimens under refrigerated conditions -7.02 % ( /- 2.80) after 60 months of storage. The negative values indicate weight loss. It can be concluded that the equation C tom = 2.36 1.29 C t12m , could explain the different results obtained when another analysis is carried out twelve months after the first one. So the different results obtained on the contradictory analysis can be justified to the Judicial Organism.
关键词：Cocaine ; Stability ; Gas chromatography ; Contradictory analysis ; Weight loss
