Secondary Electrospray Ionization Source Research Articles

Screening of biomarkers in exhaled breath of mice exposed to benzene

Objective: To screen the biomarkers in the exhaled breath of mice exposed to benzene by using exhaled breath online analysis system. Methods: Thirty 8-week-old male C57BL/6 mice were randomly divided into six groups (0, 3, 32, 324, 648, and 1 296 mg/m3) and treated with benzene vapour for 28 days. At the end of the exposure, the peripheral blood cell counts and blood glutathione (GSH) were detected. The content of malondialdehyde (MDA) in HL60 cells treated by mice plasma was examined. Exhaled breath data from mice were collected by Secondary electrospray ionization source high resolution mass spectrometry (SESI-HRMS). Targeted analysis underlying benzene metabolites and oxidative stress metabolites was performed to screen the biomarkers in exhaled breath. Results: After benzene exposure, the number of peripheral blood cells was decreased in different degrees, particularly in the white blood cells (WBC) number. The WBC in 32 and 324 mg/m3 groups was declined by 27.76% and 52.87%, respectively compared to that in control group (P<0.05). Meanwhile, compared with the control group, the GSH content of peripheral blood cells from 324 mg/m3 group decreased by 13.16% (P<0.05). In addition, MDA content was increased by 18.11% in HL60 cells treated with plasma from 324 mg/m3 group mice (P<0.05). The phenol, hydroquinone/catechol, benzenetriol and trans, trans-Muconic acid (t,t-MA) in the exhaled gas of mice could be used as biomarkers for benzene exposure (R2>0.8, P<0.001). The peak intensity of five small molecular metabolites related to oxidative stress (ω-carboxylic fatty acid C5H10O3, ω-carboxylic fatty acid C6H12O3, glutamate, cysteine and MDA) increased with the increase of benzene concentration (P<0.05), which was negatively correlated with WBC decline (P<0.001), suggesting that these molecules mignt be used as biomarkers of benzene-induced toxicity. Conclusions: Phenol, hydroquinone/catechol, benzenetriol and trans, trans-Muconic acid (t,t-MA) in exhaled breath of mice could be used as biomarkers for benzene exposure; ω-carboxylic fatty acid C5H10O3, ω-carboxylic fatty acid C6H12O3, glutamate, cysteine and MDA might be used as markers of benzene-induced toxicity.

Reagent and analyte ion hydrates in secondary electrospray ionization mass spectrometry (SESI-MS), their equilibrium distributions and dehydration in an ion transfer capillary: Modelling and experiments.

Secondary electrospray ionization (SESI) in a water spray environment at atmospheric pressure involves the reactions of hydrated hydronium reagent ions, H3 O+ (H2 O)n , with trace analyte compounds in air samples. Understanding the formation and dehydration of reagent and analyte ions is the foundation for meaningful quantification of trace compounds by SESI-mass spectrometry (MS). A numerical model based on gas-phase ion thermochemistry is developed that describes equilibria in H3 O+ (H2 O)n reagent cluster ion distributions and ligand switching reactions with polar NH3 molecules leading to equilibrated hydrated ammonium ions NH4 + (H2 O)m . The model predictions are compared with experimental results obtained using a cylindrical SESI source coupled to an ion-trap mass spectrometer via a heated ion transfer capillary. Non-polar isoprene, C5 H8 , was used to further probe the nature of the reagent ions. Equilibrium distributions of H3 O+ (H2 O)n ions and their reactions with NH3 molecules have been characterized by the model in the near-atmospheric pressure SESI source. NH3 analyte molecules displace H2 O ligands from the H3 O+ (H2 O)n ions at the collisional rate forming NH4 + (H2 O)m ions, which travel through the heated ion transfer capillary losing H2 O molecules. The data for variable NH3 concentrations match the model predictions and the C5 H8 test substantiates the notion of dehydration in the heated capillary. Large cluster ions formed in the SESI region are dehydrated to H3 O+ (H2 O)1,2,3 and NH4 + (H2 O)1,2 while passing through the heated capillary, and considerable diffusion losses also occur. This phenomenon is also predicted for other polar analyte molecules, A, that can undergo similar switching reactions, thus forming AH+ and AH+ (H2 O)m analyte ions.

Direct molecular imprinting technique to synthesize coated electrospun nanofibers for selective solid-phase microextraction of chlorpyrifos.

Molecularly imprinted-electrospun nanofibers based on the use ofpoly(vinyl alcohol) were fabricated and used as a new sorbent for solid-phase microextraction of chlorpyrifos. The molecularly imprintednanofibers were prepared by electrospinning and direct molecular imprinting of polymeric nanofibers. Poly(vinyl alcohol) was used as the functional and electrospun polymer. Chlorpyrifos was used as a template molecule, and glutaraldehyde as the cross-linker. Detection was performed by ion mobility spectrometry equipped with a secondary electrospray ionization source. The molecularly imprinted fiber has a selectivity and extraction efficiency better than the fiber fabricated using the conventional method of encapsulating MIP particles in electrospun nanofibers. Parameters affecting the extraction efficiency such as ionic strength, stirring rate, extraction time, and temperature were evaluated. The dynamic range of the method was in the range of 0.5-200μgL-1 with the limit of detection of 0.1μgL-1. The intra- and inter-day relative standard deviations of the method were 4 and 9%, respectively. The fiber-to-fiber reproducibility for three different fibers is 5%. The spiking recoveries from spiked apple, cucumber, and water samples were in the range of 82-112%. Graphical abstract Molecularly imprinted-electrospun nanofibers were fabricated based on the direct molecular imprinting technique and used as a new SPME fiber coating for selective extraction of chlorpyrifos from fruits and water samples prior its determination by secondary electrospray ionization-ion mobility spectrometry.

Effect of halide ions on secondary electrospray ionization-ion mobility spectrometry for the determination of TNT extracted by dispersive liquid-liquid microextraction

In this study, secondary electrospray ionization source (SESI) was coupled with ion mobility spectrometer (IMS) and utilized for the determination of 2,4,6-trinitrotoluene (TNT) in water and wastewater samples. The sensitivity of SESI–IMS for TNT detection was compared with that obtained by ESI–IMS. The effect of different halide ions (as dopants) on the signal enhancement was evaluated and eventually KCl was selected as the most effective dopant. Sample preparation step for the pre-concentration of TNT was performed by dispersive liquid-liquid microextraction using an extraction solvent with the lower density than water. Methanol and toluene were selected as the disperser and extraction solvents, respectively. Some other affected parameters on the extraction efficiency; such as salt addition and sample acidity were also investigated. The linearity was obtained 4.0–175.0 μg L−1 and the limit of detection and quantification were calculated 1.0 and 4.0 μg L−1, respectively. Tap, River, and laboratory wastewater samples were selected to evaluate the method capability for determining the analyte in real matrices, and satisfactory analytical results were obtained.

Expanding metabolite coverage of real-time breath analysis by coupling a universal secondary electrospray ionization source and high resolution mass spectrometry—a pilot study on tobacco smokers

Online breath analysis is an attractive approach to track exhaled compounds without sample preparation. Current commercially available real-time breath analysis platforms require the purchase of a full mass spectrometer. Here we present an ion source compatible with virtually any preexisting atmospheric pressure ionization mass spectrometer that allows real-time analysis of breath. We illustrate the capabilities of such technological development by upgrading an orbitrap mass spectrometer. As a result, we detected compounds in exhaled breath between 70 and 900 Da, with a mass accuracy of typically <1 ppm; resolutions between m/Δm 22 000 and 70 000 and fragmentation capabilities. The setup was tested in a pilot study, comparing the breath of smokers (n = 9) and non-smokers (n = 10). Exogenous compounds associated to smoking, as well as endogenous metabolites suggesting increased oxidative stress in smokers, were detected and in some cases identified unambiguously. Most of these compounds correlated significantly with smoking frequency and allowed accurate discrimination of smokers and non-smokers.

Capturing in Vivo Plant Metabolism by Real-Time Analysis of Low to High Molecular Weight Volatiles

We have deployed an efficient secondary electrospray ionization source coupled to an Orbitrap mass analyzer (SESI-MS) to investigate the emissions of a Begonia semperflorens. We document how hundreds of species can be tracked with an unparalleled time resolution of 2 min during day-night cycles. To further illustrate the capabilities of this system for volatile organic compounds (VOCs) analysis, we subjected the plant to mechanical damage and monitored its response. As a result, ∼1200 VOCs were monitored displaying different kinetics. To validate the soundness of our in vivo measurements, we fully characterized some key compounds via tandem mass spectrometry (MS/MS) and confirmed their expected behavior based on prior gas chromatography/mass spectrometry (GC/MS) studies. For example, β-caryophyllene, which is directly related to photosynthesis, was found to show a periodic day-night pattern with highest concentrations during the day. We conclude that the capability of SESI-MS to capture highly dynamic VOC emissions and wide analyte coverage makes it an attractive tool to complement GC/MS in plant studies.

Numerical modeling and experimental validation of a universal secondary electrospray ionization source for mass spectrometric gas analysis in real-time

The process by which ambient vapors are ionized upon interaction with electrosprays is not fully understood, compromising its optimization and widespread use. In this work we evaluated the different scales associated with the processes involved in secondary electrospray ionization (SESI), and developed a new numerical method that merges the analytical solution that describes the angle of aperture and the current of an ideal electrospray, with a finite element method that enables the evaluation of complex geometries. The numerical method showed that, despite the low ionization efficiency (i.e. ion concentration/neutral vapor concentration ∼10−4), depletion of neutral vapors plays an important role. We used this method to optimize and design a low flow SESI source, which was coupled with a commercial high resolution/high mass accuracy mass spectrometer. The system was designed to be interfaced with virtually any pre-existing atmospheric pressure ionization mass spectrometer. The experimental validation for the detection of ambient vapors confirmed qualitatively the numerical predictions in terms of ionization efficiency as a function of sample flow rate. As a result of the optimization, this prototype showed a 5-fold sensitivity increase against standard SESI. This novel add-on is meant to upgrade mass spectrometers to analyze trace gases in real time by SESI technique.

Analysis of human breath samples using a modified thermal desorption: gas chromatography electrospray ionization interface

A two-stage thermal desorption/secondary electrospray ionization/time-of-flight mass spectrometry for faster targeted breath profiling has been studied. A new secondary electrospray ionization (SESI) source was devised to constrain the thermal desorption plume and promote efficient mixing in the ionization region. Further, a chromatographic pre-separation stage was introduced to suppress interferences from siloxanes associated with thermal desorption profiles of exhaled breath samples.In vitro tests with 5-nonanone indicated an increased sensitivity and a lowered limit-of-detection, both by a factor of ~4, the latter to an on-trap mass of 14.3 ng, equivalent to a sampled breath concentration of 967 pptv. Analysis of the mass spectrometric responses from 20 breath samples acquired sequentially from a single participant indicated enhanced reproducibility (reduced relative standard deviations (RSD) for 5-nonanone, benzaldehyde and 2-butanone were 28 %, 16% and 14% respectively. The corresponding values for an open SESI source were that 5-nonanone was not detected, with %RSD of 39% for benzaldehyde and 31% for 2-butanone).The constrained source with chromatographic pre-separation resulted in an increase in the number of detectable volatile organic compounds (VOCs) from 260 mass spectral peaks with an open SESI source to 541 peaks with the constrained source with pre-separation. Most of the observed VOCs were present at trace levels, at less than 2.5% of the intensity of the base peak.Seventeen 2.5 dm3 distal breath samples were collected from asthma patients and healthy controls respectively, and subjected to comparative high-throughput screening using thermal desorption/SESI/time-of-flight mass spectrometry (TD-SESI-ToFMS). Breath metabolites were detected by using a background siloxane ion (hexamethylcyclotrisiloxane m/z 223.0642) as an internal lockmass. Eleven breath metabolites were selected from the breath research literature and successfully targeted. These data reinforce the proposition that TD-SESI-MS has potential for development as a rapid screening method for disease stratification and targeted metabolism profiling.

Comparison of reactant and analyte ions for 63Nickel, corona discharge, and secondary electrospray ionization sources with ion mobility-mass spectrometry

63Nickel radioactive ionization (63Ni) is the most common and widely used ion source for ion mobility spectrometry (IMS). Regulatory, financial, and operational concerns with this source have promoted recent development of non-radioactive sources, such as corona discharge ionization (CD), for stand-alone IMS systems. However, there has been no comparison of the negative ion species produced by all three sources in the literature. This study compares the negative reactant and analyte ions produced by three sources on an ion mobility-mass spectrometer: conventional 63Ni, CD, and secondary electrospray ionization (SESI). Results showed that 63Ni and SESI produced the same reactant ion species while CD produced only the nitrate monomer and dimer ions. The analyte ions produced by each ion source were the same except for the CD source which produced a different ion species for the explosive RDX than either the 63Ni or SESI source. Accurate and reproducible reduced mobility (K0) values, including several values reported here for the first time, were found for each explosive with each ion source. Overall, the SESI source most closely reproduced the reactant ion species and analyte ion species profiles for 63Ni. This source may serve as a non-radioactive, robust, and flexible alternative for 63Ni.