Characterization of Spray Modes and Factors Affecting the Ionization Efficiency of Paper Spray Ionization

Abstract

In this study, we systematically evaluated the factors affecting the ionization efficiency of paper spray ionization (PSI), such as electric field, solvent supply rate, and paper thickness and hydrophobicity. The observed paper spray plume was classified into three modes: single cone-jet, multi-jet, and rim-jet modes. With the increase in the spraying voltage, the spray plume appeared in order of single cone-jet, multi-jet, and rim-jet modes. The rim-jet mode exhibited the lowest standard deviation and high ionization efficiency among the three spray modes. The main parameter determining the spray mode was the charge density of the droplets generated by paper spray, which depends on the electric field and solvent supply rate. A thicker paper reduced the electric repulsion between the jets and lowered the threshold voltage to reach the rim-jet mode. Lowering the solvent supply rate caused mode transitions from the single cone-jet to the rim-jet, possibly due to the increased droplet charge density. The hydrophobic modification on a paper substrate led to a different ionization mechanism or electrostatic spray ionization at low applied voltages.

Rapid screening of high‐priority N‐nitrosamines in pharmaceutical, forensic, and environmental samples with paper spray ionization and filter cone spray ionization‐mass spectrometry

“…To demonstrate utility in trace screening applications, detection limits for target NAMs were established from liquid‐phase and solid‐phase matrices using PSI‐MS and FCSI‐MS, respectively. Seen in Table 1, direct deposition of individual NAMs as residues on a paper substrate was considered as a control, since limits of detection (LODs) stemming from these analyses are impacted from any substrate‐ or solvent‐related effects upon the ionization mechanism, 46,47 but matrix‐related effects are removed. Here, N ‐nitrosodiethylamine (NDEA) and N ‐nitrosodibutylamine (NDBA) demonstrated low‐nanogram LODs, whereas NDMA required deposited masses over an order of magnitude higher; the main structural fragment at m / z 58 for NDMA resides close to the LMCO for the utilized mass spectrometer, resulting in product ion instability and lower observable intensity.…”

Applications of ambient ionization mass spectrometry in 2022: An annual review

“…Given the popularity of PS ionization, numerous studies have focused on enhancing the performance of this technique and resolving some of its deficiencies, for instance by evaluating the effects of different solvents, paper types and spray modes. 176 Brown et al conducted a thorough evaluation of optimal parameters for cone spray ionization, a recently developed PS variant. 177 The study involved the evaluation of various solvents, conductive plastic materials, and cone geome- substrate for the concentration and detection of small molecules.…”

“…Other studies have focused on the improvement of existing techniques. Given the popularity of PS ionization, numerous studies have focused on enhancing the performance of this technique and resolving some of its deficiencies, for instance by evaluating the effects of different solvents, paper types and spray modes 176 . Brown et al.…”

Direct mass spectrometry analysis of biological tissue for diagnosis of thyroid cancer using wooden-tip electrospray ionization

“…These techniques employ charged microdroplets and/or laser (with or without the assistance of a matrix) to desorb and ionize analytes on a tissue surface, and can be used for tissue imaging ( Xiao et al, 2020 ; Huang et al, 2022 ). Ambient MS with paper spray ionization have been developed direct analysis of raw samples ( Wang et al, 2011 ; Cai et al, 2021 ; Nguyen et al, 2022 ; Yang et al, 2022 ). Other ambient ESI techniques for direct MS analysis of biological tissue have been also developed using different solid substrates, e.g., paper ( Wang et al, 2011 ), metal probe ( Mandal et al, 2012 ), metal foil ( So et al, 2019 ), tissue ( Hu et al, 2012 ), wooden tip ( Hu and Yao, 2018 ), and others ( Hu and Yao, 2022 ).…”