Nontarget Analysis of Urine by Electrospray Ionization-High Field Asymmetric Waveform Ion Mobility-Tandem Mass Spectrometry

Abstract

Nearly a decade after first commercialization, high field asymmetric waveform ion mobility spectrometry (FAIMS) has yet to find its place in routine chemical analysis. Prototypes have been used to demonstrate the utility of this separation technique combined with mass spectrometry (MS). Unfortunately, first generation commercial FAIMS instruments have gone practically unused by early adopters. Here, we show this to be due to poor ion transmission in the FAIMS-MS source interface. We present simple instrumental modifications and optimization of experimental conditions to achieve good performance from the first generation commercial FAIMS device (the Ionalytics Selectra) coupled to a high resolution Q-TOF-MS. In combination with nanospray ionization, we demonstrate for the first time the nontarget analysis of urine by FAIMS with minimal sample preparation. We show the unique suitability of electrospray ionization (ESI)-FAIMS-MS for identification of low abundance species such as urinary biomarkers of damage of nucleic acids in a complex biological matrix. The elimination of electrospray noise and matrix components by FAIMS and the continuous flow of analytes through FAIMS for accurate and tandem mass analysis produce high quality spectral data suitable for structural identification of unknowns. These characteristics make ESI-FAIMS-MS ideal for nontarget identification, even when compared to high efficiency LC-ESI-MS.

Detection, Identification, and Occurrence of Thiotetronic Acids in Drinking Water from Underground Sources by Electrospray Ionization-High Field Asymmetric Waveform Ion Mobility Spectrometry-Quadrupole Time-of-Flight-Mass Spectrometry

“…The nanospray source was positioned 20°off axis of the orifice of a Selectra (Ionalytics, Ottawa) FAIMS device with a modified source interface described previously. 21 The FAIMS analyzer was operated at a dispersion voltage of 4000 V, outer electrode offset of ±150 V, and a curtain plate voltage of ±1000 V. N 2 and CO 2 gases (Linde, Guelph) were purified online by charcoal/molecular sieve filters, and a dry buffer/carrier gas (80% of N 2 and 20% of CO 2 ) was introduced into the FAIMS analyzer at a flow of 2 L min −1 . A Q-TOF micro mass spectrometer (Waters, U.K.) was used as a detector and ion transmission conditions (including the cone voltage of 14 V and the collision energy of 4 V) were optimized to minimize ion dissociation.…”

Revisiting the Reactivity of Uracil During Collision Induced Dissociation: Tautomerism and Charge-Directed Processes

“…O ur recent work has been directed towards the nontarget identification of urinary biomarkers of nucleic acid damage and metabolism [1]. These compounds, which are detected as modified nucleosides or bases in urine, can provide important information about DNA [2] or RNA damage [3] that has occurred in the cell.…”

“…The identification of low abundance unknown species such as these in a complex biological sample matrix remains a significant challenge for any analytical technique. High resolution tandem mass spectrometry (MS/ MS) with a suitable analytical separation has a realistic possibility of addressing this challenge, and we have recently shown some success in this direction [1,4,5]. However, in addition to the instrumental challenges associated with acquiring high quality spectra for metabolites in urine [1], the interpretation of MS/MS data for the purpose of unknown identification remains a significant challenge.…”

“…High resolution tandem mass spectrometry (MS/ MS) with a suitable analytical separation has a realistic possibility of addressing this challenge, and we have recently shown some success in this direction [1,4,5]. However, in addition to the instrumental challenges associated with acquiring high quality spectra for metabolites in urine [1], the interpretation of MS/MS data for the purpose of unknown identification remains a significant challenge. Such de novo identification aims to correlate observed spectral features in MS/MS to the structures of investigated species based on established reactivity for a class of compounds [4,[6][7][8][9].…”

“…Ions with a fixed charge site or little conjugation can undergo charge-remote dissociation that is similar in mechanism to thermal degradation of neutral molecules [23,24]. In contrast, the small, highly conjugated ions of NA bases typically react through charge-mediated processes [1,4,6,7,18,24]. Intramolecular chemical reactions of precursor ions are initiated by a charge site, and the stability of specific conformations of precursor ions and product-ions are determined by inductive effects, steric effects, and resonance in the conjugated system of double bonds.…”