Neutral Desorption Sampling of Living Objects for Rapid Analysis by Extractive Electrospray Ionization Mass Spectrometry

Abstract

MS comes to life: A novel method to sample surfaces of biological objects uses a neutral gas beam for in vivo EESI mass spectrometric analysis without sample pretreatment (see picture; QTOF=quadropole time‐of‐flight). The sampling process results in rapid in vivo analyses with reduced ion suppression and without chemical contamination. This strategy can be used in food quality monitoring, homeland security, metabolomics, and clinical diagnosis.

Direct analysis of biological samples using extractive electrospray ionization mass spectrometry (EESI-MS)

“…In a broad sense, breath and skin analysis can be regarded as in vivo analysis as well. Chen et al [30] successfully detected nicotine on the skin of a smoker by open-air ND-EESI, and they also found caffeine on the skin 30 min after the smoker drank three cups of strong black coffee. Theoretically, in vivo sampling systems for medical research and drug development can be coupled to EESI in the same way as that for ND devices.…”

“…The analysis time of ambient MS for a biological sample is typically within a few minutes because sample preparation is minimized, which greatly increases extractable information per unit time in experiments. Ambient ionization was soon introduced into the biological field, e.g., EESI has been employed for the rapid characterization of living objects [30], native proteins [31], and metabolic biomarkers [32][33][34].…”

Commentary: Challenging convention using ambient ionization and direct analysis mass spectrometric techniques

“…Applications were shown to be varied for ESSI, sampling diverse matrices including gases (breath), aerosols (fruit ripening off-gases), surfaces (fruit), liquids (milk) and viscous wileyonlinelibrary.com/journal/rcm , the quantitative performance of ESSI (melamine in milk at levels of 500 ppb), and extending the ESSI experiment towards highly viscous matrices using a heated headspace approach derived from microjetting [15] techniques (analysis of honey (8000 cP) and toothpaste (300000 cP)) or ultrasonic sample nebulization. The second part of the lecture centred on neutral desorption ESSI (ND-ESSI), adding finesse to the ESSI experiment to allow safe, non-proximate desorption of sample surfaces using a neutral gas stream, [16] in examples such as the classification of adulterated foodstuffs such as rotting fish or meat (food safety) and the detection of explosives on human skin (security); [17] and detailing key insights into the ESSI mechanism (although still not fully understood) to elucidate the roles played by analyte solubility, liquid-liquid extraction, and ion-molecule reaction considerations, amongst others. Professor Zenobi concluded by detailing existing challenges for the ESSI family of techniques, which included robustness of the extractive (ESI-based) process, data treatment for complex samples, and achievable sensitivity for real-world applications.…”

Detection of trace levels of lead in aqueous liquids using extractive electrospray ionization tandem mass spectrometry

“…Another merit of EESI is that samples are isolated from the direct bombardment by charged particles or energetic metastable atoms, and thus EESI is a relatively soft ionization method which may help to extract valuable structure information from complexes. EESI has been applied to the rapid characterization of metabolic biomarkers in biological samples [49] and living objects [50,51], trace amounts of explosives on human skin [52], drugs [53], and proteins in solutions [54] with minimal sample pretreatment.…”