- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Evaluating the influence of laser wavelength and detection stage geometry on optical detection efficiency in a single-particle mass spectrometer
摘要： Single-particle mass spectrometry (SPMS) is a useful tool for the online study of aerosols with the ability to measure size-resolved chemical composition with a temporal resolution relevant to atmospheric processes. In SPMS, optical particle detection is used for the effective temporal alignment of an ablation laser pulse with the presence of a particle in the ion source, and it gives the option of aerodynamic sizing by measuring the offset of particle arrival times between two detection stages. The efficiency of the optical detection stage has a strong influence on the overall instrument performance. A custom detection laser system consisting of a high-powered fibre-coupled Nd:YAG solid-state laser with a collimated beam was implemented in the detection stage of a laser ablation aerosol particle time-of-flight (LAAP-TOF) single-particle mass spectrometer without major modifications to instrument geometry. The use of a collimated laser beam permitted the construction of a numerical model that predicts the effects of detection laser wavelength, output power, beam focussing characteristics, light collection angle, particle size, and refractive index on the effective detection radius (R) of the detection laser beam. We compare the model predictions with an ambient data set acquired during the Ice in Clouds Experiment – Dust (ICE-D) project. The new laser system resulted in an order-of-magnitude improvement in instrument sensitivity to spherical particles in the size range 500–800 nm compared to a focussed 405 nm laser diode system. The model demonstrates that the limit of detection in terms of particle size is determined by the scattering cross section (Csca) as predicted by Mie theory. In addition, if light is collected over a narrow collection angle, oscillations in the magnitude of Csca with respect to particle diameter result in a variation in R, resulting in large particle-size-dependent variation in detection efficiency across the particle transmission range. This detection bias is imposed on the aerodynamic size distributions measured by the instrument and accounts for some of the detection bias towards sea salt particles in the ambient data set.
关键词： LAAP-TOF,aerosol,single-particle mass spectrometry,Mie theory,laser wavelength,detection stage geometry,optical detection efficiency
更新于2025-09-23 15:19:57
-
Co Incorporated Mesoporous Carbon Material Assisted Laser Desorption/Ionization Ion Source as an on-line Interface of in vivo Microdialysis Coupled with Mass Spectrometry
摘要： The combination of microdialysis and mass spectrometry (MS) provides the potential for rapidly monitoring diverse metabolites in vivo. Unfortunately, the high concentration of salt in biological microdialysates hindered the sensitive and on-line detection of these small molecular compounds. In this study, we synthesized Co incorporated mesoporous carbon material (Co-NC), and developed Co-NC assisted laser desorption/ionization (LDI) ion source as an on-line interface of in vivo microdialysis coupled with MS for direct analysis of diverse metabolites in microdialysates. The Co-NC could be used as matrix for surface assisted laser desorption/ionization mass spectrometry (SALDI MS) analysis of small molecular compounds, even under high concentration of salt conditions. The Co-NC possessed the adsorption ability for small molecular compounds, and it was believed that the adsorption ability of Co-NC might separate the analytes from the salt in microdialysates at a microscopic level, which might facilitate the desorption and ionization of the analytes and finally improved the salt-tolerance ability as matrix. Furthermore, the Co-NC assisted LDI ion source as a novel interface of in vivo microdialysis coupled with MS has been applied to the on-line monitoring of liver metabolites from the CCl4-induced liver injury rat model for the first time.
关键词： microdialysis,Co incorporated mesoporous carbon material,metabolites,mass spectrometry,laser desorption/ionization,salt-tolerance
更新于2025-09-23 15:19:57
-
Coal Discrimination Analysis Using Tandem Laser-Induced Breakdown Spectroscopy and Laser Ablation Inductively Coupled Plasma Time-of-Flight Mass Spectrometry
摘要： The contribution and impact of combined laser ablation inductively coupled plasma time of flight mass spectrometry (LA-ICP-TOF-MS) and laser induced breakdown spectroscopy (LIBS) were evaluated for the discrimination analysis of different coal samples. This Tandem approach allows simultaneous determination of major and minor elements (C, H, Si, Ca, Al, Mg, etc), and trace elements (V, Ba, Pb, U, etc.) in the coal. The research focused on coal classification strategies based on principle component analysis (PCA) combined with K-means clustering, partial least squares discrimination analysis (PLS-DA), and support vector machine (SVM) for analytical performance. Correlation analyses performed from TOF mass and LIBS emission spectra from the coal samples showed that most major, minor, and trace elements emissions had negative correlation with the volatile content. Suitable variables for the classification models were determined from these data. The individual TOF data, LIBS data, and the combined data of TOF and LIBS, respectively, as the input for different models were analyzed and compared. In all cases, the results obtained with the combined TOF and LIBS data were found to be superior to those obtained with the individual TOF or LIBS data. The nonlinear SVM model combined with TOF and LIBS data provided the best coal classification performance, with a classification accuracy of up to 98%.
关键词： Principal component analysis,Support vector machine,Partial least squares discrimination analysis,Laser-induced breakdown spectroscopy,K-means clustering,Coal discrimination,Laser ablation inductively coupled plasma time of flight mass spectrometry
更新于2025-09-23 15:19:57
-
Direct Ultraviolet Laser-Induced Reduction of Disulfide Bonds in Insulin and Vasopressin
摘要： Ultraviolet (UV) light has been shown to induce reduction of disulfide bonds in solution. The photoreduction is proposed to be a result of electron donation from excited Tyr or Trp residues. In this work, a powerful UV femtosecond laser was used to generate photoreduced products, while the hypothesis of Tyr/Trp mediation was studied with spectroscopy and mass spectrometry. With limited irradiation times of 3 min or less at 280 nm, the laser-induced reduction in arginine vasopressin and human insulin led to significant yields of ～3% stable reduced product. The photogenerated thiols required acidic pH for stabilization, while neutral pH primarily caused scrambling and trisulfide formation. Interestingly, there was no direct evidence that Tyr/Trp mediation was a required criterion for the photoreduction of disulfide bonds. Intermolecular electron transfer remained a possibility for insulin but was ruled out for vasopressin. We propose that an additional mechanism should be increasingly considered in UV light-induced reduction of disulfide bonds in solution, in which a single UV photon is directly absorbed by the disulfide bond.
关键词： mass spectrometry,photoreduction,disulfide bonds,Tyr/Trp mediation,femtosecond laser,Ultraviolet light
更新于2025-09-23 15:19:57
-
Qualitative and Quantitative Distinction of <i>ortho</i> -, <i>meta</i> -, and <i>para</i> -Fluorotoluene by Means of Chirped Femtosecond Laser Ionization
摘要： Femtosecond-laser ionization mass spectrometry (fs-LIMS) is demonstrated to be a powerful analytical method providing access to the qualitative distinction of structural isomers of ortho-, meta-, and para-fluorotoluene. The key point of the approach presented is a systematic variation of the spectral phase of the fs-laser pulses, which characteristically affects the fragmentation pattern observed in the mass spectra. Variation of the linear chirp parameter is also helpful for rationalizing the fragmentation mechanism. Ultimately two ternary mixtures of the three title isomers are quantitatively analyzed in situ with an accuracy of 5% for the molar fractions.
关键词： structural isomers,Femtosecond-laser ionization mass spectrometry,fragmentation pattern,spectral phase,quantitative analysis,fluorotoluene
更新于2025-09-23 15:19:57
-
Localization of metabolites of human kidney tissue with infrared laser-based selected reaction monitoring mass spectrometry imaging and silver-109 nanoparticle-based surface assisted laser desorption/ionization mass spectrometry imaging
摘要： Infrared (IR) Laser Ablation-remote-Electrospray Ionization (LARESI) platform coupled to a tandem mass spectrometer (MS/MS) operated in selected reaction monitoring (SRM) or multiple reaction monitoring (MRM) modes was developed and employed for imaging of target metabolites in human kidney cancer tissue. SRM or MRM modes were employed to avoid artifacts that are present in full scan MS mode. Four tissue samples containing both cancerous and non-cancerous regions, obtained from three patients with renal cell carcinoma (RCC), were imaged. Sixteen endogenous metabolites that were reported in the literature as varying in abundance between cancerous and non-cancerous areas in various human tissues were selected for analysis. Target metabolites comprised ten amino acids, four nucleosides and nucleobases, lactate and vitamin E. For comparison purposes, images of the same metabolites were obtained with ultraviolet (UV) desorption/ionization mass spectrometry imaging (UV-LDI-MSI) using monoisotopic silver-109 nanoparticle-enhanced target (109AgNPET) in full-scan MS mode. The acquired MS images revealed differences in abundances of selected metabolites between cancerous and non-cancerous regions of the kidney tissue. Importantly, the two imaging methods offered similar results. This study demonstrates the applicability of the novel ambient LARESI SRM/MRM MSI method to both investigating and discovering cancer biomarkers in human tissue.
关键词： biomarker,cancer,chemical engineering,mass spectrometry,kidney,imaging,clear cell renal cell carcinoma
更新于2025-09-23 15:19:57
-
Advantages and Limitations of Laser-Assisted Mass Spectrometry for the Local Determination of the Trace Element Composition of Fluid Inclusions in Quarzites in the Bural-Sardyk Deposit (Vostochny Sayan, Buryatia)
摘要： The effect of laser radiation on the surface and volume of natural quartz of the Bural-Sardyk deposit (East Sayan, Buryatia) is studied. The influence of the main parameters of laser radiation with a wavelength of 213 nm (prefix NWR-213) and the properties of the sample on the results of elemental mass spectrometric analysis with inductively coupled plasma are established. The features of laser ablation of various microinclusions in quartz are considered. The main problems arising from the laser evaporation of fluid inclusions in quartzites for the quantitative determination of their chemical composition are indicated.
关键词： superquartzite,fluid inclusions,LA-ICP-MS,inductively coupled plasma mass spectrometry,laser ablation,quartz
更新于2025-09-23 15:19:57
-
Optimization of Measuring Parameters for Two-dimensional Elemental Mapping in Laser-induced Breakdown Optical Emission Spectrometry Using 1-kHz Q-switched Nd:YAG Laser
摘要： This paper described how the lateral resolution of an elemental mapping was estimated in laser-induced breakdown optical emission spectrometry (LIBS), when the focus point of a high-frequency Q-switched Nd:YAG laser was moved on a sample surface, along with measuring the emission signal from the resultant plasma. Several measuring parameters were optimized to improve the lateral resolution; namely, they were an averaged laser power of 1 mJ/pulse, a laser repetition frequency of 1 kHz, a scanning rate of the laser beam of 0.5 mm/s, and an atmospheric gas pressure of He 1 000 Pa. Using these optimal parameters, a lateral resolution was obtained to be ca. 20 μm in the one-dimensional direction of laser scan. Furthermore, two model samples, in which regularly-aligned copper circles were deposited on a nickel plate, were irradiated by a scanning laser beam to determine actual resolving abilities both in a line direction along travelling the laser and in a two-dimensional direction over a certain sample area. The sample having an interval of 85 μm between the copper circles could give an emission image which was appropriately resolved in the two-dimensional as well as the one-dimensional direction; however, in the other sample having the 25-μm interval, the two-dimensional resolution became degraded compared to the resolution of the line scan, probably because the ablation grooves, which were left on the sample surface, had a width of more than 100 μm and were overlapped with each other in the observed area.
关键词： lateral resolution,copper,scanning laser beam,laser-induced breakdown plasma spectrometry,laser ablation
更新于2025-09-23 15:19:57
-
Application of Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging for Evaluating the Quality of Fish Fillets
摘要： Consumption of fish is rapidly increasing worldwide. It is important to evaluate fish fillet quality because fish undergoes physical and chemical changes during frozen storage. Fish fillets exhibit formaldehyde (FA) accumulation from the decomposition of trimethylamine N-oxide. FA is a powerful protein denaturant; thus, it is important to avoid FA buildup during fish processing to preserve fish quality, especially texture. To determine where FA accumulates, in order to maintain the quality of fish fillets, we performed matrix-assisted laser desorption/ionization mass spectrometry imaging, aiming to identify muscle-derived peptides, which reflect conditions such as denaturation and/or aggregation. We used frozen sections from which lipophilic molecules were washed out and detected various peptide peaks. Furthermore, we tried to identify indices to represent fish fillet softening by protease treatment. We could detect characteristic peaks owing to FA and protease treatment; the findings were consistent with the results of texture profiles showing fish fillet’s real solidity. These molecules might thus serve as effective markers to evaluate fish fillet quality.
关键词： mass spectrometry imaging,peptide,matrix-assisted laser desorption/ionization,protease,formaldehyde
更新于2025-09-23 15:19:57
-
Investigating the Effects of Chemical Gradients on Performance and Reliability within Perovskite Solar Cells with TOF-SIMS
摘要： Time-of-flight secondary-ion mass spectrometry (TOF-SIMS), a powerful analytical technique sensitive to all components of perovskite solar cell (PSC) materials, can differentiate between the various organic species within a PSC absorber or a complete device stack. The ability to probe chemical gradients through the depth of a device (both organic and inorganic), with down to 100 nm lateral resolution, can lead to unique insights into the relationships between chemistry in the absorber bulk, at grain boundaries, and at interfaces as well as how they relate to changes in performance and/or stability. In this review, the technique is described; then, from the literature, several examples of how TOF-SIMS have been used to provide unique insight into PSC absorbers and devices are covered. Finally, the common artifacts that can be introduced if the data are improperly collected, as well as methods to mitigate these artifacts are discussed.
关键词： perovskite solar cells,time-of-flight secondary-ion mass spectrometry,performance,degradation
更新于2025-09-23 15:19:57