F. Huang, K.K. Murray, “Continuous flow infrared matrix‐assisted laser desorption electrospray ionization mass spectrometry,” 24 (2010) 2799–2804. doi:10.1002/rcm.4704.

Abstract: Continuous flow infrared matrix-assisted laser desorption electrospray ionization (CF IR MALDESI) mass spectrometry was demonstrated for the on-line analysis of liquid samples. Samples in aqueous solution were flowed through a 50mm i.d. fused-silica capillary at a flow rate of 1–6mL/min. As analyte aqueous solution flowed through the capillary, a liquid sample bead formed at the capillary tip. A pulsed infrared optical parametric oscillator (OPO) laser with wavelength of 2.94mm and a 20Hz repetition rate was focused onto the capillary tip for sample desorption and ablation. The plume of ejected sample was entrained in an electrospray to form ions by MALDESI. The resulting ions were sampled into an ion trap mass spectrometer for analysis. Using CF IR MALDESI, several chemical and biochemical reactions were monitored on-line: the chelation of 1,10-phenanthroline with iron(II), insulin denaturation with 1,4-dithiothreitol, and tryptic digestion of cytochrome c.

CF IR MALDESI MS interface
Schematic of the CF IR MALDESI MS interface showing the nanospray source, capillary, liquid sample bead, IR laser beam and mass spectrometer orifice (RCM 2010; 24: 2799)
CF IR MALDESI mass spectra of insulin reduction
CF IR MALDESI mass spectra of (a) 500 mM insulin in 50 mM NH4HCO3 water buffer solution, (b) 500 mM insulin mixed with 100 mM 1,4-dithiothreitol (DTT) reducing agent, and (c) denatured insulin b chain after on-line mixing of 500mM insulin with 100mM DTT solution (RCM 2010; 24: 2799)