High-Field Asymmetric Ion Mobility Spectrometry (FAIMS) is a technique for ion separation and detection based on ion mobility variation under high electronic field. While compensation voltage scanning speed is a fundamental parameter in FAIMS, its impact on spectra remains unclear. In this work, a function referred to as F-EMG is introduced to describe the impact of compensation voltage scanning speed on FAIMS spectra, and the properties of the function are studied. Theoretical analysis emphasizes the impact of the scanning speed on peak height, position, and symmetry, as well as the capability of the F-EMG function to progressively approach Gaussian function at lower scanning speeds. Furthermore, the function indicates that spectra obtained in positive and negative scanning modes exhibits symmetry. An experimental validation, conducted with a custom FAIMS setup and analyzing hydrogen sulfide, ethylbenzene, toluene, styrene, benzene and ammonia, confirms the model's influence on peak features, fitting accuracy, and exhibits a closer alignment with the Gaussian function at lower scanning speeds. Additionally, the experimental data indicate that the spectra show symmetry in positive and negative scanning models. This work not only improves understanding of FAIMS spectral analysis but also introduces a robust method for enhancing data accuracy across varying scanning speeds.

Dual ionization sources combining an ultraviolet (UV) lamp source and a corona discharge (CD) source were first used as ionization sources for high-field asymmetric waveform ion mobility spectrometry (FAIMS) to switch ionization modes without changing hardware. The CD source was manufactured using a tungsten needle and a copper ring and its usability was verified. The UV source and the CD source were combined into the FAIMS sensor and multiple ionization modes were attempted by controlling their on-off status. The optimal flow rate, quantitative and qualitative capabilities of the system were investigated, and the experiments on the impact of humidity and interferent on the system were conducted. The experimental results indicated that the flow rate of 3-4 L/min could ensure sufficient sensitivity and resolution of the system. The dual ionization sources configuration provided richer qualitative and quantitative information for FAIMS. This platform could operate in three ionization modes and had the potential to expand the analyzable compounds of UV-FAIMS. In summary, the research demonstrates that the dual ionization sources could be used as ionization sources for FAIMS, and the combined system provided convenience for chemical analysis.

High-field asymmetric waveform ion mobility spectrometry (FAIMS) enables precise identification of substances through fingerprint spectra obtained by multi-cycle scans at different separation voltages (DV) and nonlinear functions. To improve the scan speed of compensating voltage (CV) in multi-cycle scanning, the challenge arises in peak position shifts. This article proposes a method to accurately determine peak positions regardless of scan speed by exploiting the symmetric features of spectra obtained through positive and negative CV scans. The proposed method enables extremely fast scan speeds. A custom-built FAIMS system was used to verify the correlation between peak shifts and scan speed, the symmetry of spectra peaks under positive and negative CV scan modes, and the peak positions and solution errors of nonlinear functions by using benzene, styrene, acetone, toluene, m-xylene, and hydrogen sulfide as experimental samples. The results demonstrate the widespread occurrence of peak shifts, with peak deviations reaching as high as 2.49% even in slow scans of 0.75 V/s. As scan speed increases, peak position deviations gradually increase, with the maximum deviation reaching 46.83% at a scan speed of 30 V/s. By applying the proposed averaging method, peak positions of the six substances were obtained within the scan speed range of 30 to 0.75 V/s. Compared to traditional methods, the maximum peak position error using the averaging method was reduced by approximately 87.5%, and the spectrum acquisition time was reduced by 85%. The use of the averaging method reduced the calculation error of the alpha function by 88% and decreased the acquisition time by 80%. The research findings of this study offer a solution for the accurate determination of peak positions in FAIMS under fast scanning.

Soy sauce, an important condiment, varies greatly in the brand, geographical distribution, and production processes. We investigated the potential of volatile organic compounds (VOCs) serving as an indicator of soy sauce quality to detect three regions and two production technologies of Chinese soy sauce. An analytical method named high-field asymmetric waveform ion mobility spectrometry (FAIMS) was utilized for acquiring sample data. Wavelet packet decomposition (WPD) and principal component analysis (PCA) were used to extract the features of FAIMS data. 4 machine learning models were trained using these features, and the optimal parameters were obtained by a grid search. The scatter plots of the optimal two features we selected showed that the different regions and production technologies of soy sauce had obvious clustering trends. For the identification of different regions and production technologies, the training score, test score, and average cross-validation score of the optimal model were all 100%. Furthermore, the learning curves indicated that the optimal model obtained good performance and had low prediction errors. It was concluded that FAIMS combined with a suitable machine learning algorithm can successfully classify different regions and production technologies of Chinese soy sauce.

In the past two decades, miniature mass spectrometers have developed rapidly as the requirements of on-site detection have been growing continuously. At present, it seems that further miniaturization of mass spectrometers meets its bottleneck, since the traditionally used processing technologies have been approaching to their limitations. MEMS (micro-electro mechanical systems) is a widely used microfabrication technology which provides new solutions for the next generation of miniature mass spectrometers or MEMS mass spectrometers. Over the past three decades, a large number of key components of mass spectrometers, e.g., ion sources, mass analyzers, ion detectors, vacuum pumps and gauges, monolithic integrated mass spectrometer chips and so on, have all been microfabricated successfully. The development of MEMS mass spectrometers is ready for more rapid growth. In the article, the latest progress of MEMS mass spectrometers, potential applications, existing problems and challenges as well as future trends were reviewed.

A novel mass spectrometric method for probing the flash chemistry of electrogenerated reactive intermediates was developed based on rapid collision mixing of electrosprayed microdroplets by using a theta-glass capillary. The two individual microchannels of the theta-glass capillary are asymmetrically or symmetrically fabricated with a carbon bipolar electrode to produce intermediates in situ. Microdroplets containing the newly formed intermediates collide with those of the invoked reactants at sub-10 microsecond level, making it a powerful tool for exploring their ultrafast initial transformations. As a proof-of-concept, we present the identification of the key radical cation intermediate in the oxidative dimerization of 8-methyl-1,2,3,4-tetrahydroquinoline and also the first disclosure of previously hidden nitrenium ion involved reaction pathway in the C-H/N-H cross-coupling between N,N'-dimethylaniline and phenothiazine.

As the cutoff frequency of InP HEMTs enters the terahertz band, high frequency measurement and modeling techniques in hundreds of gigahertz become urgent needs for further millimeter monolithic integrated circuits design. We proposed a new de-embedding method linking device measurements and modeling based on full EM simulation data acquired from HFSS and advanced design system (ADS). The simulation results for passive dummy structures are well consistent with experiments, and the de-embedding method is proved very effective for a resistive passive device with high distributed embedding surroundings in frequency range below 40 GHz. Based on these experimental facts, the EM simulations were extended up to 300 GHz and corresponding de-embedding deviation was further investigated. Results show that the proposed de-embedding method has very high accuracy in the whole frequency region with a maximum S-parameters deviation of only 2.58%. However, further analysis proves that the small residual errors still significantly affect extracted small signal model parameters of InP HEMTs especially for transit time tau. Thus, further improvements on de-embedding accuracy or careful considerations of more error functions in modeling process are necessary for obtaining physically meaningful model parameters.

AbstractWe report a new mass spectrometric method for detecting electrogenerated intermediates. This approach is based on simultaneous activation of electrospray ionization and redox reaction on a wireless bipolar ultramicroelectrode, which is fabricated in the tip of a quartz nanopipette. The hollow structure of the ultramicroelectrode permits rapid transferring the transient species from electrode–electrolyte interfaces into the gas phase for mass spectrometric identification on the time scale of microseconds. The long‐sought fleeting intermediates including TPrA.+, whose lifetime in solution is only 200 μs, and catecholamine o‐semiquinone radicals, the second‐order rate constant of which is typically 109 m−1 s−1, were successfully identified, helping clarify the previously hidden reaction pathways. Accordingly, our method may have wide applicability in exploring the dynamics of many electrochemical reactions, especially their ultrafast initial steps.

A novel simultaneous detection method for isomers by spectrometry feature acquisition-separation parameter optimization-isomer analysis was proposed and verified. Dependent on self-made UV-FAIMS instrument , we investigated the separation of o-, m-, p-xylene by high-field asymmetric waveform ion mobility spectrometry (FAIMS) . By analyzing the spectrometry feature of xylene isomers , the characteristic peaks of o-, m- and p-xylene were extracted; by analyzing the relationship between dispersion voltage and characteristic peak position, the best separation voltage range was determined to be 550-800 V, and by further analyzing of superimposing spectrometry , the best separation voltage was found to be 700 V under the carrier gas flow rate to be 400 L/h. Under this experimental condition, the peak positions of o-, m-, p-xylene characteristic ions were 4. 36 , 14. 96 and 11. 16 V , which kept a great spacing and maintained a fairly good one-to-one correspondence to xylene mixture detection spectrometry (Peak positions 4. 33 , 14. 71 and 11. 25 V) with errors of only 0.03 , 0. 25 and 0.09 V. The experiment realized the simultaneous separation and detection of the xylene mixture, and the result verified the correctness of the isomer detection method. Under the premise of retaining the characteristic peak , the detection limit of m-xylene was 0. 047 mg/m(3), which was less than the indoor air detection amount of 0. 20 mg/m(3) specified in the national standard GB/T 18883-2002, and the linear range was 0. 24-2. 4 mg/m(3). This study provided technical support 14 the detection of xylene isomers, and provided a methodological basis for the rapid and high-precision detection of isomers by UV-FAIMS.

Carrier gas mixing as one of the most important methods to improve the separation ability of high Field Asymmetric waveform Ion Mobility Spectrometry (FAIMS) has been widely used in the field of bio macromolecule mass spectrometry, while there is a lack of some research in environmental small molecules. In this paper, five typical volatile organic compounds (VOCs), including o-xylene, isobutanol, n-hexane, acetic acid and acetone, were chosen to study the effect of N-2-He mixing ratio on the peak position, resolution and ion pass rate of monomers and dimer ion. The results showed that with the increase of the proportion of He in the carrier gas of FAIMS, the peak position of the monomer and dimer ion in five VOCs shifts, and the peak of the monomer and the dimer were different, and the monomer peak shift increased first and then decreased, while the dimer peak position shift increased gradually. With the increase of the percentage of He, the resolution of FAIMS for aliasing peaks of five VOCs gradually increased and tended to saturate at last, where the saturated helium ratio was: 20%, 30%, 10%, 40% and 20%, respectively. In addition, with the increase of the percentage of helium, the signal intensity of o-xylene, isobutanol, n-hexane and acetone had no obvious change, while that of acetic acid decreased significantly. This study provided a feasible method for improving the separation ability of FAIMS and validating the effectiveness of Blanc's law under high electric field applied in the field of small molecules.

>Both the LUNA(Laboratory for Underground Nuclear Astrophysics)collaboration in Europe and the JUNA(Jinping Underground Laboratory for Nuclear Astrophysics)collaboration in China are planning to study the key reactions during the stellar helium burning at or close to their stellar energies in deep underground laboratories[1-3].The success of such experiments relies on the ratio of the reaction yield

In this article, the normalized excitation spectra corresponding to 616 and 470 nm fluorescence and normalized fluorescence spectrum excited by 335 nm of Eu doped polymer fiber of different concentration are analyzed and compared to indicate the possibility of Eu2+ and Eu3+ ions' coexistence. And the spectra analysis shows fractal clusters' existence in higher concentration. At the same time, the clusters' existence was proved by near-field results of scanning near-field optical microscopy.