Forensic Toxicology and Antidoping, University-Hospital of Padova, Via Falloppio 50, 35121 Padova, Italy.
Anal Bioanal Chem. 2010 Apr;396(7):2435-40. doi: 10.1007/s00216-009-3387-3. Epub 2010 Jan 10.
The sensitivity and specificity of a novel method of screening for cocaine in hair, based on matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry (MS), have been evaluated. The method entails a rapid extraction procedure consisting of shaking 2.5 mg pulverised hair at high frequency in the presence of an acidic solution (160 microL of water, 20 microL of acetonitrile and 20 microL of 1 M trifluoroacetic acid) and a stainless-steel bullet. Following centrifugation, the supernatant is dried under a nitrogen stream, and the residue is reconstituted in 10 microL of methanol/trifluoroacetic acid (7:3; v/v). One microlitre of the extract is deposed on a MALDI sample holder previously scrubbed with graphite; an alpha-cyano-4-hydroxycinnamic acid (matrix) solution is electrosprayed over the dried sample surface to achieve a uniform distribution of matrix crystals. The identification of cocaine is obtained by post-source decay experiments performed on its MH(+) ion (m/z 304), with a limit of detection of 0.1 ng/mg of cocaine. A total of 304 hair samples were analysed in parallel by MALDI-MS and a reference gas chromatography-MS method. The obtained results demonstrate specificity and sensitivity of 100% for MALDI-MS. Evidence of cocaine presence was easily obtained even when hair samples exhibiting particularly low cocaine levels (<0.5 ng/mg) were analysed.
基于基质辅助激光解吸/电离（MALDI）质谱（MS）的新型可卡因毛发筛查方法的灵敏度和特异性已得到评估。该方法需要一种快速提取程序，包括在酸性溶液（160 μL 水、20 μL 乙腈和 20 μL 1 M 三氟乙酸）和不锈钢子弹存在的情况下高频摇晃 2.5 mg 粉碎的毛发。离心后，将上清液在氮气流下干燥，将残留物在 10 μL 甲醇/三氟乙酸（7:3；v/v）中重新配制。将 1 μL 提取物沉积在先前用石墨擦洗过的 MALDI 样品架上；将α-氰基-4-羟基肉桂酸（基质）溶液电喷雾到干燥的样品表面上，以实现基质晶体的均匀分布。通过对其 MH(+)离子（m/z 304）进行源后降解实验来鉴定可卡因，可卡因的检测限为 0.1 ng/mg。总共 304 个毛发样本通过 MALDI-MS 和参考气相色谱-MS 方法平行分析。所得结果表明 MALDI-MS 的特异性和灵敏度均为 100%。即使分析显示可卡因水平特别低（<0.5 ng/mg）的毛发样本，也能轻松获得可卡因存在的证据。
