Hair analysis for cocaine: factors in laboratory contamination studies and their relevance to proficiency sample preparation and hair testing practices

Since the introduction in 2001 of a urine-based detection method for recombinant erythropoietin (rHuEPO), transfusion-doping practices have regained interest. To address this problem, an efficient antidoping test designed to obtain direct proof of allogeneic blood transfusion was developed and validated. This test, based on flow cytometry analysis of red blood cell (RBCs) phenotypes, was used to determine the absence or the presence of numerous RBCs populations in a blood sample. A such, it may constitute a direct proof of an abnormal blood population resulting from homologous transfusion. Single-blind and single-site studies were carried out to validate this method as a forensic quality standard analysis and to allow objective interpretation of real cases. The analysis of 140 blood samples containing different percentages (0-5%) of a minor RBCs population were carried on by four independent analysts. Robustness, sensitivity, specificity, precision and stability were assessed. ISO-accredited controls samples were used to demonstrate that the method was robust, stable and precise. No false positive results were observed, resulting in a 100% specificity of the method. Most samples containing a 1.5% minor RBCs population were unambiguously detected, yielding a 78.1% sensitivity. These samples mimicked blood collected from an athlete 3 months after a homologous blood transfusion event where 10% of the total RBCs present in the recipient originated in the donor. The observed false negative results could be explained by differences in antigen expression between the donor and the recipient. False negatives were more numerous with smaller minor RBCs populations. The method described here fulfils the ISO-17025 accreditation and validation requirements. The controls and the methodology are solid enough to determine with certainty whether a sample contains one or more RBCs populations. This variable is currently the best indicator for homologous blood transfusion doping.     

气相色谱法测定白芥子挥发油中异硫氰酸烯丙酯的含量

目的 采用气相色谱法测定白芥子挥发油中异硫氰酸烯丙酯的含量。方法 采用水蒸气蒸馏法进行挥发油提取,通过气相色谱法测定异硫氰酸烯丙酯含量。色谱柱：RTX-5毛细管柱(30 m×0.53 mm×3.0 μm);进样口温度：230 ℃;检测器温度：260 ℃;载气为高纯氮气, 流速为3 ml/min;进样方式为分流进样,分流比为10〖DK〗∶1;进样量：2 μl。结果 异硫氰酸烯丙酯在10～100 μg/ml范围内线性关系良好（r=0.999 6）;平均回收率为97.64%（RSD=2.39%）。结论 本方法简单、灵敏、重复性好,可用于白芥子挥发油中异硫氰酸烯丙酯的含量测定。