Validation of a fast screening method for the detection of cocaine in hair by MALDI-MS.
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.
Vogliardi
Susanna
S
Forensic Toxicology and Antidoping, University-Hospital of Padova, Via Falloppio 50, 35121 Padova, Italy.
Favretto
Donata
D
Frison
Giampietro
G
Maietti
Sergio
S
Viel
Guido
G
Seraglia
Roberta
R
Traldi
Pietro
P
Ferrara
Santo Davide
SD
D003042:Cocaine / Q000032:analysis*; D006197:Hair / Q000737:chemistry*; D006801:Humans; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D015813:Substance Abuse Detection / Q000379:methods*
D003042:Cocaine