Rapid desorption of low-volatility compounds in liquid droplets accompanied by the flash evaporation of solvent below the Leidenfrost temperature.

Abstract

The objective of this work is to study the interaction of methanol droplets with the heated surface for the improved detection of low-volatility and thermally labile compounds by the flash evaporation that occurs below the Leidenfrost temperature. 5 μL solutions of low-volatility compounds in methanol were introduced into the heated tube. Desorbed analytes were ionized in the sealed atmospheric pressure chemical ionization (APCI) source by direct current (DC) corona discharge using air as the reagent gas. The rapid desorption of low-volatility compounds accompanied by the flash evaporation of methanol solvent was observed in the temperature range of 60-100°C. Linear relationships between the signal intensities and the solute concentrations in the range of 0.01-5 ppm for morphine, cocaine, methamphetamine, and amphetamine were obtained at 95°C. The observed rapid desorption of low-volatility compounds below the Leidenfrost temperature would provide useful information in many fields, e.g., the interaction of liquid droplets with heated matter, liquid sample introduction into the injection port of a gas chromatograph, coupling of the flash evaporation with pulse valve operated miniaturized mass spectrometer, etc.