Validation of a fast screening method for the detection of cocaine in hair by MALDI-MS

Abstract

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.

A tutorial on the validation of qualitative methods: From the univariate to the multivariate approach

“…Other examples of univariate methods based on visual and instrumental signals can be found elsewhere [2,[37][38][39].…”

Screening and quantitation of multiclass drugs of abuse and pharmaceuticals in hair by fast liquid chromatography electrospray time-of-flight mass spectrometry

“…This is solved when using liquid chromatography with traditional detectors [6,18,22,29], or coupled to different mass spectrometry detectors as triple quadrupole [23,24], ion trap [15], time-of-flight mass spectrometry [14] or hybrid linear ion trap-orbitrap mass spectrometry [31,32]. The use of direct mass spectrometric techniques such as ambient ionization mass spectrometry [33] and Matrix-Assisted Laser Desorption Ionization Mass Spectrometry (MALDI-MS) [34] have been also described for drug testing in hair extracts.…”

Imaging of methamphetamine incorporated into hair by MALDI-TOF mass spectrometry

“…For drugs in hair, Vogliardi et al [14] recently attempted direct detection of cocaine and its metabolites in hair using MALDI-MS with various sample preparation methods, including pulverization and extraction. However, they concluded that the extraction of analytes by incubating hair (preferably pulverized) in an acidic solvent was necessary, and demonstrated that the application of MALDI-MS to direct detection of drugs in hair is difficult [15] because of their low concentrations (ng/mg levels) and strong binding to the hair matrix [3][4][5].…”