Carbon Dioxide Microbubble Bursting Ionization Mass Spectrometry

Abstract

Aerosols generated by bubble bursting have been proved to promote the extraction of analytes and have ultrahigh electric fields at their water–air interfaces. This study presented a simple and efficient ionization method, carbon dioxide microbubble bursting ionization (CDMBI), without the presence of an exogenous electric field (namely, zero voltage), by simulating the interfacial chemistries of sea spray aerosols. In CDMBI, microbubbles are generated in situ by continuous input of carbon dioxide into an aqueous solution containing low-concentration analytes. The microbubbles extract low- and high-polarity analytes as they pass through the aqueous solution. Upon reaching the water–air interface, these microbubbles burst to produce charged aerosol microdroplets with an average diameter of 260 μm (8.1–10.4 nL in volume), which are immediately transferred to a mass spectrometer for the detection and identification of extracted analytes. The above analytical process occurs every 4.2 s with a stable total ion chromatogram (relative standard deviation: 9.4%) recorded. CDMBI mass spectrometry (CDMBI-MS) can detect surface-active organic compounds in aerosol microdroplets, such as perfluorooctanoic acid, free fatty acids epoxidized by bubble bursting, sterols, and lecithins in soybean and egg, with the limit of detection reaching the level of fg/mL. In addition, coupling CDMBI-MS with an exogenous voltage yields relatively weak gains in ionization efficiency and sensitivity of analysis. The results suggested that CDMBI can simultaneously accomplish both bubbling extraction and microbubble bursting ionization. The mechanism of CDMBI involves bubbling extraction, proton transfer, inlet ionization, and electrospray-like ionization. Overall, CDMBI-MS can work in both positive and negative ion modes without necessarily needing an exogenous high electric field for ionization and quickly detect trace surface-active analytes in aqueous solutions.

Ultrasensitive and Green Bubbling Extraction Strategies: An Extensible Solvent-Free Re-Enrichment Approach for Ultratrace Pollutants in Aqueous Samples

“…Carbon dioxide was selected as the BE gas because of its advantages over other gases. First, CO 2 has a superior response in MS, resulting in a higher sensitivity and lower LODs. , Additionally, CO 2 has a greater enrichment efficiency than the other gases, as demonstrated in Figure S3, which is consistent with the results of previous studies. , For a certain mass of PAHs, the smaller the diameter of the device, the greater the amount of aerosol adsorbed on the SPME coating. Moreover, increasing the diameter reduced the peak area (Figure S4).…”

“…21,22 Additionally, CO 2 has a greater enrichment efficiency than the other gases, as demonstrated in Figure S3, which is consistent with the results of previous studies. 21,22 For a certain mass of PAHs, the smaller the diameter of the device, the greater the amount of aerosol adsorbed on the SPME coating. Moreover, increasing the diameter reduced the peak area (Figure S4).…”

“…Our previous study demonstrated that direct ionization of microbubbles can simultaneously achieve high-sensitivity enrichment for analytes . A CO 2 bubbling extraction system further supports the hypothesis that the concentrated aerosols in BE are diluted again by water molecules sputtering out of an aqueous solution at a certain enrichment node.…”

Microdroplet accelerated reaction for high-efficiency carbon disulfide conversion

“…[16][17][18] These differences arise due to the high specific surface area of the gas/liquid interface, which can significantly accelerate chemical reactions. 19,20 A strong electric field and high reactant concentrations at the droplet interface further contribute to the acceleration of these reactions. [21][22][23] Previous research has demonstrated the feasibility of promoting amine reactions with carbon dioxide (CO 2 ) through electrospray ionization (ESI) 24 and using NH 4 HCO 3 as a CO 2 source.…”

“…Our previous bubble bursting studies have demonstrated the generation of high electric fields similar to those observed in ESI mechanisms. 20 However, the requirement for non/low-toxicity in practical application settings led us to explore the potential application of bubble bursting in the spontaneous reaction between amines in EtOH and CS 2 in the air, as depicted in our proposed application scenario (Fig. 4a).…”