How do cocaine and morphine in methanol solution desorb at the last moment of Leidenfrost phenomenon-assisted thermal desorption?

RATIONALE: The objective of the present study is to investigate desorption of low-volatility analytes in Leidenfrost phenomenon-assisted thermal desorption (LPTD).

METHODS

LPTD was investigated for 5 μL solutions of 0.03 ppm cocaine or morphine in methanol (sample weight: 0.12 ng) by using heated metal surfaces (240°C) polished by abrasives with grit numbers from #5000 (~3 μm) to #100 (~200 μm).

RESULTS

The analyte signals were detected only after the complete evaporation of methanol solvent and the formed analyte residues levitated on the heater surface. The strongest ion signals were obtained with grit number #100.

CONCLUSIONS

Because the analyte residue does not come into contact with the heated surface but levitates on the hot substrate after the evaporation of the solvent, thermal decomposition of the analyte is largely suppressed. This is a great merit of LPTD for trace analysis of low-volatility and thermally labile compounds.