A cautionary note on the effects of laboratory air contaminants on ambient ionization mass spectrometry measurements

Abstract

The common practice in MS analysis of subtracting a background air spectrum may not be appropriate if the presence of ionizable air contaminants alters the spectrum in unexpected ways. For example, VOCs released into air from floor stripping and waxing are capable of causing ion suppression of target analytes.

Role of Gas-Phase Halogen Bonding in Ambient Chemical Ionization Mass Spectrometry Utilizing Iodine

“…60−66 Because the ionization is generally carried out at atmospheric pressure in room air, other trace species in addition to the analyte are ionized concomitantly. If these species occur in a high enough concentration, they may alter the ionization of the analyte, 60 but with care, these complications can be minimized and taken into account.…”

“…Among these are direct analysis in real time mass spectrometry (DART–MS), extractive electrospray ionization mass spectrometry (EESI–MS), and easy ambient sonic spray ionization mass spectrometry (EASI–MS). The advantage of these methods is being able to analyze a variety of samples without the need for collection or sample workup, such as particles on the fly − and gases. − Because the ionization is generally carried out at atmospheric pressure in room air, other trace species in addition to the analyte are ionized concomitantly. If these species occur in a high enough concentration, they may alter the ionization of the analyte, but with care, these complications can be minimized and taken into account.…”

“…Some of these ambient methods rely on plasmas to generate the ionization agents. ,,,− One such plasma source utilizes a piezoelectric discharge, which has been used to vaporize and ionize analytes in a stream of liquid solvent and to identify gaseous contaminants in room air . Piezoelectric discharge guns (PDGs) are inexpensive and widely available because they are used to remove static charges from surfaces.…”

“…The PDG generates a pulse of both positive ions (trigger compression) and negative ions (trigger release) in a single manual “squeeze and release” cycle via mechanical distortion of a piezoelectric element. Previous studies have shown that ionization using piezoelectric devices results in soft ionization similar to DART or APCI, typically involving the addition of a proton from protonated water clusters or removal of a proton by O 2 – . ,, …”

Ambient Ionization Mass Spectrometry Today and Tomorrow: Embracing Challenges and Opportunities

“…AIMS typically works in the open atmosphere; random fluctuations of ambient conditions, such as gas flow from air conditioners or rapidly moving personnel, temperature and humidity changes, and laboratory air contaminants, can lead to large variances in the mass spectra. 27 Relative humidity variation occurring in a laboratory environment can result in ion fragmentation during DART 28 (Figure 3c) and FAPA 29 ionization. DESI spray is subjected to frequent electrical discharges under dry air conditions, resulting in unstable ionization and poor imaging quality.…”