Polymer Track Membranes for Extraction of Ions from Aqueous Solutions at Atmospheric Pressure

Abstract

The possibility of the application of the electromembrane technique for production of ions of biological molecules at atmospheric pressure is demonstrated. This technique has previously only been used for extraction of ions from liquids directly into vacuum. The membrane technique for ion extraction at atmospheric pressure was tested with both time-of-flight and Fourier transform ion cyclotron resonance mass spectrometers. The mass spectra of intact molecular ions obtained from aqueous solutions of peptides and proteins are presented. The possible mechanisms of non-destructive ion extraction are discussed. The new technique is promising for achieving absolute sensitivity (charging every analyte molecule) and for performing spatially-resolved analysis of liquid biological samples.

Polymer track membranes for atmospheric pressure field extraction of ions from liquid solutions

“…It should be mentioned that although the overall current through the source was significantly lower than the 30 nA used in [5], irreversible changes in the polymer surface of the membrane could be observed by visual inspection. It appears that such physical changes are the factor that limits the long-term operation of this source.…”

“…Decreasing the average current of the ion source in comparison with that used in [5] gave enhanced long-term stability of the ion current. As seen in fig 4, the time available for uninterrupted work with the ion source can be more then 30 minutes, and when used with a fixed small volume of liquid, is similar to nanospray.…”

“…As was shown in [5], the ion current from a membrane source is a series of peaks initiated by pulsed breakdown of the gas. To provide more reproducible results, a sharp extracting electrode was introduced to decrease the energy of the breakdown pulses (fig.2).…”

“…This is very similar to the design used in [5] but there is an additional possibility to provide a flow of the liquid sample so that a small amount of sample comprising a few μL fills the shallow cavity behind the membrane. The flow of the liquid sample was 200 μL/h.…”

“…The possibility of applying such membranes for generating ions at atmospheric pressure was demonstrated in [5] for water and water/alcohol mixtures. Although the new atmospheric pressure technique was promising as it achieved high efficiency of transfer of liquid phase ions into the gas phase, long-term instability in the ion yield from the liquid was observed, despite the relatively high stability of the current maintained through the membrane.…”