Organic secondary ion mass spectrometry: Signal enhancement by water vapor injection

Abstract

The enhancement of the static secondary ion mass spectrometry (SIMS) signals resulting from the injection, closely to the sample surface, of H 2 O vapor at relatively high-pressure, was investigated for a set of organic materials. While the ion signals are generally improved with increasing H 2 O pressure upon 12 keV Ga ϩ bombardment, a specific enhancement of the protonated ion intensity is clearly demonstrated in each case. For instance, the presence of H 2 O vapor induces an enhancement by one order of magnitude of the [M ϩ H] ϩ static SIMS intensity for the antioxidant Irgafos 168 and a ϳ1.5-fold increase for polymers such as poly(vinyl pyrrolidone).

A mixed cluster ion beam to enhance the ionization efficiency in molecular secondary ion mass spectrometry

“…By injection of water vapor ~1 mm above the target surface at a pressure of ~10 −3 mbar, an order of magnitude enhancement of the ion signal was observed for various amino acids and peptides. [4] Our laboratory has proposed that dynamically created protons formed during depth profiling experiments can provide a path for ion enhancement via [M+H] + formation. [5],[6] Finally, it has recently been demonstrated that direct bombardment of a surface with [H 2 0] 1000 + can lead to more than an order of magnitude enhancement of a variety of molecules, ranging from lipids to peptides to drugs compared with Ar 1000 + bombardment.…”

Label free biochemical 2D and 3D imaging using secondary ion mass spectrometry

“…42,43 A method of globally increasing ionisation of secondary species is the current ‘holy grail’ in ToF-SIMS development. The presence of water (and/or ice) on 28 and in the sample has shown varying enhancement for species where ion formation is through proton transfer with experiments reported where water has been squirted onto the sample during analysis 44 . Alternatively developments in laser post ionisation of the neutral portion of the secondary species (>99% of ejected material) have the potential to deliver huge increases in signal if the problem of photon induced fragmentation can be overcome.…”

Mass spectrometry imaging and profiling of single cells

“…Controlling the sublimation-condensation equilibrium of water on the sample surface during analysis has been shown to enhance ion yields by up to two-fold during depth profiling experiments [93, 94]. Surprisingly, leaking water vapor directly over the sample has also produced significant enhancement of analyte detection [95]. Post-desorption photoionization is another way to generate more detectable ions from the neutral molecules that comprise the vast majority of desorption events [96].…”