MALDI-TOF and MALDI-FTICR imaging mass spectrometry of methamphetamine incorporated into hair

A new approach is described for imaging mass spectrometry (IMS) of methamphetamine (MA) incorporated into human hair using matrix-assisted laser desorption/ionization (MALDI)-time-of-flight (TOF) and MALDI-Fourier transform ion cyclotron resonance (FTICR). A longitudinal section of a lengthwise manually-cut single human hair shaft from a chronic MA user was directly analyzed by MALDI-TOF-IMS after deposited with α-Cyano-4-hydroxycinnamic acid matrix. A barcode-like image, which was most probably generated with repeated intakes of MA, was for the first time obtained by monitoring MA-specific product ion in the selected reaction monitoring mode. Laser beam scan lengthwise-cut hair shafts gave only poor mass spectra of MA, probably due to the loss of MA and/or the thermal denaturation of hair. The identity of MA detected in hair was further confirmed by MALDI-FTICR mass spectrometry. A combination with ultra-high resolution mass spectrometry by FTICR provided indisputable identification of MA. The MALDI-FTICR-IMS of another hair shaft from the same MA user also provided a barcode-like image by monitoring the protonated molecule of MA with ultra-high resolution. The two barcode-like images exhibited a close resemblance. Thus, MALDI-IMS can offer a new perspective: 'imaging hair analyses for drugs'.