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A novel ion optical optimization method for planar multireflection time-of-flight mass spectrometry (MR-TOFMS) is introduced in this paper. The multiparameters of the gridless mirror model, including geometric and voltage parameters, are automatically optimized using a self-made program created in SIMION 8.1. Combining with the hill climbing algorithm and parallel computing technique, this method substantially enhances optimization efficiency and accuracy. The fitting results demonstrated that the ion optical performance of the gridless mirror reached up to fourth-order isochronicity with respect to the energy spread and third-order isochronicity with respect to the spatial and angular spread. As a result, the gridless mirror model achieved an aberration limit resolution of 1.7 million under realistic ion beam conditions. Due to constraints of periodic lenses, the aberration limit resolution of the planar MR-TOFMS was optimized to 600k. These results indicate that the hill climbing algorithm is an effective method to search the optimal solutions in complex ion optical systems. [ABSTRACT FROM AUTHOR]

Miniature ion trap mass spectrometry with the unique ability of tandem-in-time analysis is extensively used in public security and environmental pollution detection. In this study, a novel radial electric field driven collision-induced dissociation (REFD-CID) is presented with high fragmentation efficiency for different species by adjusting the float DC, the initial kinetic energy of ions, and the pressure in a miniature continuous atmospheric pressure interfaced ion trap mass spectrometer (CAPI-ITMS). It is noteworthy that multiple fragment ions ([M+H-nC2H4]+, where n = 1, 2, 3) of triethyl phosphate were observed with a single injection of ions. The underlying mechanism of the REFD-CID revealed that the enhanced radial electric field by modulation of the float DC drove ions toward regions of intense RF field where broadband heating and dissociation of ions took place through theoretical simulations. Finally, the REFD-CID was utilized to improve the instrument performances. The existence of reagent ions led to a severe space charge effect as the ion injection duration of the CAPI-ITMS was extended to enhance the sensitivity of aniline. Through selective fragmentation of reagent ions, peak broadening and mass shift were eliminated, and meanwhile, a 28-fold improvement of aniline in a signal-to-noise ratio was achieved with the ion injection duration varying from 50 to 2500 ms. Moreover, isomeric illicit drugs (JWH-018 and acetylcodeine) were distinguished by generating multiple characteristic fragment ions, demonstrating potential applications in the identification of synthetic illicit drugs. [ABSTRACT FROM AUTHOR]

Ion gate is a key buildup for drift tube ion mobility spectrometry (IMS) and its combination with mass spectrometry. Bradbury-Nielsen gate, as the most commonly used ion gate in IMS, possesses a distinct ion mobility discrimination effect due to its depletion features. This impedes the scaling of the ion gate opening time to improve the separation capability of IMS while keeping its sensitivity for multiple ion species. In this work, a Tyndall-Powell gate (TPG) simply composed of two identical wire grids was used to develop an ion gate with nearly no ion mobility discrimination for IMS. Experimental results showed that the TPG features a gate region where the electric field for opening the gate could be enhanced to effectively solve the ion mobility discrimination problem related to it. Meanwhile, enhancing that electric field enabled the TPG-IMS to keep a resolving power over 106 at 100 °C for ion peak with a signal-to-noise ratio up to 800. With that TPG-IMS, baseline separation of two ion peaks, the hydronium and the acetone monomer peaks with a reduced mobility difference of only 0.04 cm2 V-1 s-1, was achieved with no sensitivity loss for the least mobile acetone dimer ions. [ABSTRACT FROM AUTHOR]

Quadrupole devices are widely used as ion analyzers and ion guides, which are usually driven by a sinusoidal waveform. Recently, these devices driven by a digital waveform have attracted much attention. Driven by different rf waveforms, the pseudopotential well depth of quadrupole devices is significantly different, which will affect their performance. However, there is a lack of comprehensive view on the performance differences of quadrupole devices or hybrid instrument driven by different rf waveforms. In this paper, the differences in mass range, resolution, sensitivity, and ion fragmentation of LIT/TOFMS driven by square and sinusoidal waveforms were investigated. Compared with the sinusoidal mode, the square mode had a wider mass range and better mass resolution. Toluene was used to study the difference in sensitivity and ion fragmentation between the two modes. The results showed that the sensitivity of the square mode was 1.7–2.5 times that of the sinusoidal mode at different ion densities. According to the sensitivity differences, it was inferred that the ion-trapping efficiency and ion capacity of LIT in the square mode were 2.0 times and 1.7 times those in sinusoidal mode. It was found that the square mode behaved "softer" and presented less fragmentation, and the proportion of fragment ions in the sinusoidal mode can reach 3.2 times that in the square mode at high ion density. Therefore, LIT/TOFMS driven by a square waveform shows greater potential in the application of the complex matrix system with a wide mass range. [ABSTRACT FROM AUTHOR]

The specific locations of the double bonds in linear olefins can facilitate olefin catalytic synthetic reactions to improve the quality of target olefin products. We developed a simple and efficient approach based on single photon ionization time-of-flight mass spectrometry (SPI-TOFMS) combined with online ozonolysis to identify and quantify the linear olefin double bond positional isomers. The online ozonolysis cleaved the olefins at the double bond positions that led to formation of corresponding characteristic aldehydes. The aldehydes were then detected by SPI-TOFMS to achieve unique spectrometric 'fingerprints' for each linear olefin to successfully identify the isomeric ones. To accurately quantify the isomeric components in olefin mixtures, an algorithm was proposed to quantify three isomeric olefin mixtures based on characteristic ion intensities and their equivalent ionization coefficients. The relative concentration errors for the olefin components were lower than 2.5% while the total analysis time was less than 2 min. These results demonstrate that the online ozonolysis SPI-TOFMS has the potential for real-time monitoring of catalytic olefin synthetic reactions. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

On-line monitoring of propofol in exhaled air is a potential way to evaluate the anaesthesia depth for patients during surgery. In this study, a negative Ni ionization high resolution ion mobility spectrometer with Bradbury-Nielsen-Gate-Grid structure was built to measure propofol with reactant ions Cl(HO) using dichloromethane as dopant. Instead of forming three propofol ions (M - H), M · O, and (M - H) with reactant ions O(HO), only product ion M · Cl was produced when introducing dichloromethane gas. The peak-to-peak resolution ( R) between reactant ions Cl(HO) and product ion M · Cl was 17.4, which was 1.6 times larger than that between O(HO) and product ion. Furthermore, the linear response range using reactant ions Cl(HO) was 3.5 times wider than that obtained with reactant ions O(HO). [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Pure INCO, ISCN, and the hitherto unknown molecule ISeCN have been prepared in the HeI photoelectron spectrometer (PES) by the heterogeneous reactions of ICI gas with AgNCO, AgSCN at room temperature, and AgSeCN at -9 (±1) °C, respectively. They were characterized on line by PES experiments and OVGF calculations. The well-matched results between the PES experiments and OVGF calculations not only show that the new reaction is a good reaction to prepare pure INCO and pure ISCN, but also that the new compound prepared by passing the ICI gas over the freshly AgSeCN powder at -9(±1) °C is the hitherto unknown ISeCN. [ABSTRACT FROM AUTHOR]