4 research outputs found
Carbon Dioxide Microbubble Bursting Ionization Mass Spectrometry
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
Generating Electrospray Ionization on Ballpoint Tips
In this study, we report a simple
and economical ballpoint electrospray
ionization mass spectrometry (BP-ESI-MS) technique. This combines
a small ballpoint tip with a syringe pump for the direct loading and
ionization of various samples in different phases (including solution,
semisolid, and solid) and allows for additional applications in surface
analysis. The tiny metal ball on the ballpoint tip exhibits a larger
surface for ionization than that of a conventional sharp tip end,
resulting in higher ionization efficiency and less sample consumption.
The adamant properties of the ballpoint tip allow sampling by simply
penetrating or scraping various surfaces, such as a fruit peel, paper,
or fabric. Complex samples, such as fine herbal powders and small
solid samples, could be stored in the hollow space in the ballpoint
socket and subsequently extracted online, which greatly facilitated
MS analysis with little to no sample preparation. Positive ion mode
was attempted, and various compounds, including amino acids, carbohydrates,
flavonoids, and alkaloids, were detected from different types of samples.
The results demonstrated that the special and excellent physical characteristics
of ballpoint tips allowed for fast and convenient sampling and ionization
for mass spectrometry analysis by the BP-ESI-MS method
Nickel-Catalyzed Reductive Three-Component Cross-Coupling of Butadiene with Aldehydes and Alkenyl Triflates/Bromides: Access to Skipped Dienes
A regio- and stereoselective nickel-catalyzed
reductive three-component
cross-coupling of 1,3-butadiene with aldehydes and alkenyl triflates
or bromides was realized. This protocol afforded a convenient approach
to the synthesis of skipped diene compounds bearing various functionals
and heterocyclic groups. The utility of this reaction was also demonstrated
by scale-up preparation and diverse transformations
Enantioselective Ir-Catalyzed Allyl Alkylation/Semipinacol Rearrangement
The
semipinacol rearrangement is a powerful and versatile method
for constructing all-carbon quaternary stereocenters. The development
of catalytic asymmetric semipinacol rearrangements using multifunctionalizable
electrophiles remains highly sought-after in organic synthesis. In
this study, a catalytic enantioselective allylic cation-induced semipinacol
rearrangement reaction was presented that enables the simultaneous
construction of two skipped chiral carbon centers. Chiral Ir(I)-(P,olefin)
and Sc(OTf)3 catalysts cooperatively initiate the asymmetric
allylic alkylation of alkenyl cyclobutanols with allylic alcohols,
triggering ring expansion of the cyclobutanol moiety through a stereoselective
1,2-alkyl migration. The reaction afforded a range of cyclopentanones
bearing an α-quaternary carbon that is adjacent to a chiral
allyl scaffold. The products were applied to synthesize enantioenriched
fused tricyclopentanoids bearing four stereogenic carbon centers