6 research outputs found
Dopant-Assisted Positive Photoionization Ion Mobility Spectrometry Coupled with Time-Resolved Thermal Desorption for On-Site Detection of Triacetone Triperoxide and Hexamethylene Trioxide Diamine in Complex Matrices
Peroxide explosives, such as triacetone
triperoxide (TATP) and
hexamethylene trioxide diamine (HMTD), were often used in the terrorist
attacks due to their easy synthesis from readily starting materials.
Therefore, an on-site detection method for TATP and HMTD is urgently
needed. Herein, we developed a stand-alone dopant-assisted positive
photoionization ion mobility spectrometry (DAPP-IMS) coupled with
time-resolved thermal desorption introduction for rapid and sensitive
detection of TATP and HMTD in complex matrices, such as white solids,
soft drinks, and cosmetics. Acetone was chosen as the optimal dopant
for better separation between reactant ion peaks and product ion peaks
as well as higher sensitivity, and the limits of detection (LODs)
of TATP and HMTD standard samples were 23.3 and 0.2 ng, respectively.
Explosives on the sampling swab were thermally desorbed and carried
into the ionization region dynamically within 10 s, and the maximum
released concentration of TATP or HMTD could be time-resolved from
the matrix interference owing to the different volatility. Furthermore,
with the combination of the fast response thermal desorber (within
0.8 s) and the quick data acquisition software to DAPP-IMS, two-dimensional
data related to drift time (TATP: 6.98 ms, <i>K</i><sub>0</sub> = 2.05 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>; HMTD: 9.36 ms, <i>K</i><sub>0</sub> = 1.53 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>) and desorption time
was obtained for TATP and HMTD, which is beneficial for their identification
in complex matrices
Long-Term Real-Time Monitoring Catalytic Synthesis of Ammonia in a Microreactor by VUV-Lamp-Based Charge-Transfer Ionization Time-of-Flight Mass Spectrometry
With
respect to massive consumption of ammonia and rigorous industrial
synthesis conditions, many studies have been devoted to investigating
more environmentally benign catalysts for ammonia synthesis under
moderate conditions. However, traditional methods for analysis of
synthesized ammonia (e.g., off-line ion chromatography (IC) and chemical
titration) suffer from poor sensitivity, low time resolution, and
sample manipulations. In this work, charge-transfer ionization (CTI)
with O<sub>2</sub><sup>+</sup> as the reagent ion based on a vacuum
ultraviolet (VUV) lamp in a time-of-flight mass spectrometer (CTI-TOFMS)
has been applied for real-time monitoring of the ammonia synthesis
in a microreactor. For the necessity of long-term stable monitoring,
a self-adjustment algorithm for stabilizing O<sub>2</sub><sup>+</sup> ion intensity was developed to automatically compensate the attenuation
of the O<sub>2</sub><sup>+</sup> ion yield in the ion source as a
result of the oxidation of the photoelectric electrode and contamination
on the MgF<sub>2</sub> window of the VUV lamp. A wide linear calibration
curve in the concentration range of 0.2–1000 ppmv with a correlation
coefficient (<i>R</i><sup>2</sup>) of 0.9986 was achieved,
and the limit of quantification (LOQ) for NH<sub>3</sub> was in ppbv.
Microcatalytic synthesis of ammonia with three catalysts prepared
by transition-metal/carbon nanotubes was tested, and the rapid changes
of NH<sub>3</sub> conversion rates with the reaction temperatures
were quantitatively measured with a time resolution of 30 s. The high-time-resolution
CTI-TOFMS could not only achieve the equilibrium conversion rates
of NH<sub>3</sub> rapidly but also monitor the activity variations
with respect to investigated catalysts during ammonia synthesis reactions
Simple and Integrated Spintip-Based Technology Applied for Deep Proteome Profiling
Great
efforts have been taken for developing high-sensitive mass
spectrometry (MS)-based proteomic technologies, among which sample
preparation is one of the major focus. Here, a simple and integrated
spintip-based proteomics technology (SISPROT) consisting of strong
cation exchange beads and C<sub>18</sub> disk in one pipet tip was
developed. Both proteomics sample preparation steps, including protein
preconcentration, reduction, alkylation, and digestion, and reversed
phase (RP)-based desalting and high-pH RP-based peptide fractionation
can be achieved in a fully integrated manner for the first time. This
easy-to-use technology achieved high sensitivity with negligible sample
loss. Proteomic analysis of 2000 HEK 293 cells readily identified
1270 proteins within 1.4 h of MS time, while 7826 proteins were identified
when 100000 cells were processed and analyzed within only 22 h of
MS time. More importantly, the SISPROT can be easily multiplexed on
a standard centrifuge with good reproducibility (Pearson correlation
coefficient > 0.98) for both single-shot analysis and deep proteome
profiling with five-step high-pH RP fractionation. The SISPROT was
exemplified by the triplicate analysis of 100000 stem cells from human
exfoliated deciduous teeth (SHED). This led to the identification
of 9078 proteins containing 3771 annotated membrane proteins, which
was the largest proteome data set for dental stem cells reported to
date. We expect that the SISPROT will be well suited for deep proteome
profiling for fewer than 100000 cells and applied for translational
studies where multiplexed technology with good label-free quantification
precision is required
Simple and Integrated Spintip-Based Technology Applied for Deep Proteome Profiling
Great
efforts have been taken for developing high-sensitive mass
spectrometry (MS)-based proteomic technologies, among which sample
preparation is one of the major focus. Here, a simple and integrated
spintip-based proteomics technology (SISPROT) consisting of strong
cation exchange beads and C<sub>18</sub> disk in one pipet tip was
developed. Both proteomics sample preparation steps, including protein
preconcentration, reduction, alkylation, and digestion, and reversed
phase (RP)-based desalting and high-pH RP-based peptide fractionation
can be achieved in a fully integrated manner for the first time. This
easy-to-use technology achieved high sensitivity with negligible sample
loss. Proteomic analysis of 2000 HEK 293 cells readily identified
1270 proteins within 1.4 h of MS time, while 7826 proteins were identified
when 100000 cells were processed and analyzed within only 22 h of
MS time. More importantly, the SISPROT can be easily multiplexed on
a standard centrifuge with good reproducibility (Pearson correlation
coefficient > 0.98) for both single-shot analysis and deep proteome
profiling with five-step high-pH RP fractionation. The SISPROT was
exemplified by the triplicate analysis of 100000 stem cells from human
exfoliated deciduous teeth (SHED). This led to the identification
of 9078 proteins containing 3771 annotated membrane proteins, which
was the largest proteome data set for dental stem cells reported to
date. We expect that the SISPROT will be well suited for deep proteome
profiling for fewer than 100000 cells and applied for translational
studies where multiplexed technology with good label-free quantification
precision is required
Deep Metaproteomics Approach for the Study of Human Microbiomes
Host–microbiome
interactions have been shown to play important
roles in human health and diseases. Most of the current studies of
the microbiome have been performed by genomic approaches through next-generation
sequencing. Technologies, such as metaproteomics, for functional analysis
of the microbiome are needed to better understand the intricate host–microbiome
interactions. However, significant efforts to improve the depth and
resolution of gut metaproteomics are still required. In this study,
we combined an efficient sample preparation technique, high resolution
mass spectrometry, and metaproteomic bioinformatics tools to perform
ultradeep metaproteomic analysis of human gut microbiome from stool.
We reported the deepest analysis of the microbiome to date with an
average of 20 558 protein groups identified per sample analysis.
Moreover, strain resolution taxonomic and pathway analysis using deep
metaproteomics revealed strain level variations, in particular for <i>Faecalibacterium prausnitzii</i>, in the microbiome from the
different individuals. We also reported that the human proteins identified
in stool samples are functionally enriched in extracellular region
pathways and in particular those proteins involved in defense response
against microbial organisms. Deep metaproteomics is a promising approach
to perform in-depth microbiome analysis and simultaneously reveals
both human and microbial changes that are not readily apparent using
the standard genomic approaches
Sensitive Detection of Black Powder by a Stand-Alone Ion Mobility Spectrometer with an Embedded Titration Region
Sensitive
detection of black powder (BP) by stand-alone ion mobility
spectrometry (IMS) is full of challenges. In conventional air-based
IMS, overlap between the reactant ion O<sub>2</sub><sup>–</sup>(H<sub>2</sub>O)<sub><i>n</i></sub> peak and the sulfur
ion peak occurs severely; and common doping methods, providing alternative
reactant ion Cl<sup>–</sup>(H<sub>2</sub>O)<sub><i>n</i></sub>, would hinder the formation of ionic sulfur allotropes. In
this work, an ion mobility spectrometer embedded with a titration
region (TR-IMS) downstream from the ionization region was developed
for selective and sensitive detection of sulfur in BP with CH<sub>2</sub>Cl<sub>2</sub> as the titration reagent. Sulfur ions were
produced via reactions between sulfur molecules and O<sub>2</sub><sup>–</sup>(H<sub>2</sub>O)<sub><i>n</i></sub> ions
in the ionization region, and the remaining O<sub>2</sub><sup>–</sup>(H<sub>2</sub>O)<sub><i>n</i></sub> ions that entered the
titration region were converted to Cl<sup>–</sup>(H<sub>2</sub>O)<sub><i>n</i></sub> ions, which avoided the peak overlap
as well as the negative effect of CH<sub>2</sub>Cl<sub>2</sub> on
sulfur ions. The limit of detection for sulfur was measured to be
5 pg. Furthermore, it was demonstrated that this TR-IMS was qualified
for detecting less than 5 ng of BP and other nitro-organic explosives