Simulation study of three new quadrupole ion funnels to improve low-mass ion transmission.

RATIONALE: By applying radio frequency (RF) and direct current (DC) voltages to corresponding ring electrodes, ion funnel (IF) can efficiently focus and transmit ions. However, IF has an inherent mass discrimination problem that will greatly limit low mass-to-charge (m/z) ion focusing and transmission. To improve the transmission efficiency (TE) of the IF, this paper explores three new profile quadrupole ion funnels (QIF). METHODS: Computer simulations of the potential field distributions of QIFs and conventional IFs were performed to assess their focusing characteristics. To compare the TE, ion optics simulation programs SIMION and AXSIM were used to perform a series of simulations. Three QIF types (toroidal, cylindrical, and hyperbolic configurations) were used to improve ion TE, and their transmission and focus performance were also compared with conventional IF. RESULTS: By simulating the trajectories of ions in the IF, the optimum electrical parameters for three new QIFs were obtained and compared with conventional IFs, with TE improvements recorded for m/z < 100 of 16%, 20%, and 13%. CONCLUSIONS: The results indicate that studying these three new IF configurations has great research significance for improving sensitivity to low m/z ions in mass spectrometer instruments.

Synchronized Reverse Scan Collision Induced Dissociation in Digital Ion Trap Mass Spectrometer for Improving Fragment Ion Detection.

Development of fragment ion detection methods is of great importance for mass spectrometer advancement or substance identification. To date, collision induced dissociation (CID) remains the most commonly used ion activation method in MS/MS experiments, and the effectiveness of CID in an ion trap mass spectrometer is limited by low mass cutoff and weak fragmentation yields. Theoretically, controlling the q value is the key to maintain the fragment efficiency and trapping efficiency of MS/MS, thus improving the detection of fragment ion, while currently reported techniques usually require complex circuitry and often produce different CID patterns. In this paper, with the developed synchronized reversed scanning-collision induced dissociation (SRS-CID) technique, we demonstrate its effective improvement in fragment ion detection. The SRS-CID is implemented on a digital ion trap mass spectrometer (DITMS) by reverse scanning the q values during CID process, or specifically, the frequency is increased during the CID process. With the SRS-CID technique, the fragmentation efficiency of precursor ions can be slightly improved. For reserpine analyte, the trapping efficiency for low-mass fragment ions is improved at least 3 times, and for YGGFL, the trapping efficiency for low-mass fragment ions is improved at least 9 times. These experimental results can also be validated by simulations, and the kinetic energy variation plot suggests consecutive fragmentation occurs. In any case, the SRS-CID provides a solution to the low efficiency of fragment ion detection during tandem MS analysis, which will certainly be useful in the future.

Recognition of Cis-Trans and Chiral Proline and Its Derivatives by Ion Mobility Measurement of Their Complexes with Natamycin and Metal Ion.

Discrimination of isomers is an important and valuable feature in many analytical applications, and the identification of chiral isomers and cis-trans isomers is the current research focus. In this work, a simple method for direct, simultaneous recognition of d-/l-proline (P), d-/l-/cis-/trans-4-hydroxyproline (4-HP), and d-/l-/cis-/trans-N-tert-butoxycarbony (N-Boc-4-HP) was investigated by means of trapped ion mobility spectrometry-mass spectrometry (TIMS-MS). The isomers with cis-/trans-/d-/l-configuration can be directly recognized based on their mobility upon reaction with natamycin (Nat) and metal ions through noncovalent interactions. The results indicate that the recognition of the enantiomers has certain specificity, and the structural difference of the enantiomers was increased in a complex with Nat and metal ions. Herein, d-/l-P can be recognized through the ternary complexes [P + Nat + Mg - H]+, [P + 2Nat + Ca - H]+, [P + 2Nat + Mn - H]+, and [P + Nat + Cu - H]+. Similarly, c-4-HPL, c-4-HPD, t-4-HPL, and t-4-HPD can be recognized by [4-HP + Nat + Ca - H]+, [4-HP + 2Nat + Ca - H]+, and [4-HP + Nat + Cu - H]+, while N-Boc-c-4-HPL, N-Boc-c-4-HPD, N-Boc-t-4-HPL, and N-Boc-t-4-HPD were recognized through the enantiomer complexes [N-Boc-4-HP + Nat + Li]+, [N-Boc-4-HP + Nat + 2Na - H]+, [N-Boc-4-HP + Nat + K]+, [N-Boc-4-HP + Nat + Mn - H]+, and [N-Boc-4-HP + Nat + Ba - H]+. Moreover, tandem mass spectrometry (MS/MS) results indicated that different collision energies were obtained for the same fragment ions, which implied that the enantiomer complexes that contributed to their mobility separation shared identical interaction mode but had different gas-phase rigid geometries. Furthermore, the relative quantification for the enantiomers was performed, and the results were supported by a satisfactory coefficient (R2 > 0.99). The developed method can provide a promising and powerful strategy for the separation of chiral proline and its d-/l-/cis-/trans derivatives, bearing the advantages of higher speed, better accuracy, high selectivity, and no need for chemical derivatization and chromatographic separation.

Genetic algorithm parallel optimization of a new high mass resolution planar electrostatic ion trap mass analyzer.

The study and design of high-resolution mass analyzers is a very important task in mass spectrometry. A planar electrostatic ion trap (PEIT) mass analyzer with image charge detection and FT-based data processing has been developed, theoretically simulated, and experimentally validated. However, the 10 ring electrode configuration (PEIT-10) is difficult for mechanical construction and voltage tuning; moreover, few methods have been reported for optimizing the performance of multi-electrode mass analyzers. In this article, a simplified PEIT-7 mass analyzer was designed, and a genetic algorithm parallel optimization (GAPO) method was developed for optimizing multiple voltage settings of the new PEIT-7 mass analyzer to achieve spatial and energy isochronicity as well as iso-coordinate property. The automatic voltage optimization processes for the reduction of time aberration and spatial aberration showed that the developed GAPO method can significantly improve the optimization efficiency (the optimal voltage set being found within 5 hours with a maximum time aberration of 15 ps and a maximum z aberration of 0.10 µm). Based on the results obtained from the GAPO method, the resolving power of the PEIT-7 mass analyzer for six groups of ions with closely packed masses (m/z = 117.000 Th to 117.010 Th) was demonstrated, and a mass resolution of 171k was achieved at an acquisition time of 200 ms. The established GAPO method facilitates the design and optimization of high-resolution mass analyzers and may be useful for the design of other multi-electrode ion optical devices.

A Ti/Nb-functionalized COF material based on IMAC strategy for efficient separation of phosphopeptides and phosphorylated exosomes.

In this work, on the basis of an immobilized metal ion affinity chromatography enrichment strategy, a new kind of covalent organic framework (COF) material for enrichment of phosphorylated peptides and exosomes was successfully prepared in a facile method, and Ti4+ and Nb5+ were used as dual-functional ions (denoted as COF-S-S-COOH-Ti4+/Nb5+). With the advantage of unbiased enrichment towards phosphopeptides, COF-S-S-COOH-Ti4+/Nb5+ shows ultra-high selectivity (maximum molar ratio of ß-casein: BSA is 1:20,000) and low limit of detection (0.2 fmol). In addition, the material has an excellent phosphopeptide loading capacity (100 µg/mg) and reusability (at least seven times). Furthermore, applying the material to the actual sample, 4 phosphopeptides were selectively extracted from the serum of renal carcinoma patients. At the same time, exosomes with an intact structure in the serum of renal carcinoma patients were successfully isolated rapidly using this strategy. All experiments have shown that COF-S-S-COOH-Ti4+/Nb5+ exhibits exciting potential in practical applications.

Application of the poly (POSS-octavinyl-co-N-methylacetamide-co-divinylbenzene) solid extraction column in analyzing preservatives.

In this study, a special poly solid-phase extraction (in-tube SPE) column consisting of poly (POSS-octavinyl-co-N-methylacetamide-co-divinylbenzene) [poly (POSS-OS-co-DVB-co-NMA)] was prepared based on the chemical structure of the preservatives, and was used as medium for extraction analysis in combination with UPLC. The composition of polymer SPE was optimized and characterized; good scanning electron microscopy (SEM) properties and satisfactory porosity were obtained with 30% monomer (POSS-OS:DVB:NMA = 2 wt%:13 wt%:15 wt%) and 70 wt% porogenic solvent (PEG20000:DMSO:ACN = 10 wt%:50 wt%:10 wt%). The experimental parameters of the in-tube SPE-UPLC analysis were optimized systematically. Then, the in-tube SPE-UPLC method was applied for analyzing the beverage sample, and correlation coefficients (R2) > 0.99 were obtained for the linear relationship within limits of 0.1~5.0 µg mL-1. Excellent extraction efficiency, good precision, and satisfactory limit of detection sensitivity between 0.03 and 0.10 µg mL-1 were obtained. The recovery ranged from 71.5 to 88.0%, with RSD ≤ 6.1%. Furthermore, the proposed method has the features of simple sample pretreatment, high throughput, rapid analysis, cost-effectiveness, and satisfactory sensitivity. Hence, the developed in-tube SPE-UPLC method based on the poly (POSS-OS-co-DVB-co-NMA) SPE column can be potentially used for simple and sensitive detection of preservatives.

Identification of Bi-2-naphthol and Its Phosphate Derivatives Complexed with Cyclodextrin and Metal Ions Using Trapped Ion Mobility Spectrometry.

The separation of chiral enantiomers has gained increasing importance in many research fields, becoming a major research hotspot. 1,1'-Bi (2-naphthol) (BINOL) and 1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (BNP) are referred to as atropisomer chiral molecules, which are essential chiral catalysts and intermediates in several reactions. In this work, BINOL and BNP atropisomers are separated and identified using trapped ion mobility spectrometry (TIMS) to monitor the different mobilities of their derivative complexes. The latter are obtained by the simple mixing of BINOL/BNP, cyclodextrin (CD), and the metal ions through noncovalent interactions. The results indicate that the enantiomer complexes of BINOL/BNP can be separated with a certain specificity, showing that R-, S-BINOL can be separated by the ternary complexes of [BINOL+γ-CD + Rb]+, [BINOL+γ-CD + Cu-H]+, and [BINOL+ß-CD + Cu-H]+ based on the difference in their mobility; similarly, the R-, S-BNP enantiomer can be isolated by the formed ternary complexes of [BNP+α-CD + Ba-H]+, [BNP+ß-CD + Co-H]+, [BNP+ß-CD + Ca-H]+, [BNP+ß-CD + Cu-H]+, [BNP+ß-CD + Fe-H]+, [BNP+ß-CD + Li]+, and [BNP+ß-CD + Sr-H]+. Furthermore, the peak separation rate (Rp-p) of the complexes was calculated, with the Rp-p of the three enantiomers of BINOL being 1.130 and the Rp-p of the seven complexes of BNP reaching 2.089. At last, the different survival yields for the collision energies were found for the enantiomer complexes, revealing the rigid structural differences in the stereospecificity of the enantiomer complexes that result in the separation by the TIMS. Additionally, due to the advantages of simple operation, fast speed, and high sensitivity and because chemical derivatization and chromatographic separation are not required, the developed method can provide a promising and powerful strategy for the separation and identification of binaphthyl derivatives or even other enantiomers of the reaction intermediates.

Enantio-separation of pregabalin by ternary complexation using trapped ion mobility spectrometry.

Rationale The rapid identification of small-molecule chiral drugs is challenging due to subtle structural differences. Different enantiomers of chiral drugs may produce inverse biological effects through their different pharmacokinetics. Therefore, it is highly desirable to distinguish the chirality of drug molecules. METHODS: The chirality of pregabalin was distinguished by studying the ion mobility spectra of the ternary non-covalent complexes formed with cyclodextrins (CDs), pregabalin, and alkali-earth cations using trapped ion mobility spectrometry (TIMS). The ternary non-covalent complex ions were determined by electrospray ionization of mixed solutions. The analyzed sample was simply mixed, without derivatization or sample pretreatment. The relative contents of pregabalin enantiomers were derived using a calibration curve method. RESULTS: The ion mobility spectra of several ternary non-covalent complexes formed with α-, ß-, and γ-CD, pregabalin, and alkali-earth cations were obtained. We compared their ability to distinguish the chirality of pregabalin. The best peak-to-peak resolution (Rp-p ) was estimated to be 2.20 for [2ß-CD + pregabalin + Sr]2+ , which can be ascribed as baseline separation. The derived relative contents for S-pregabalin were in agreement with the actual contents. CONCLUSIONS: A novel and convenient method for discriminating the chirality of the pregabalin molecule by TIMS was developed and optimized. The chirality of pregabalin was recognized by studying the ion mobility spectra of the ternary non-covalent complexes, such as [2ß-CD + pregabalin + Sr]2+ . This TIMS method could also be used to quantify the relative contents of pregabalin enantiomers.

Measurement of the effective electric field radius on digital ion trap spectrometer.

The effective electric field radius is a fundamental parameter of ion traps, and it has a significant influence on ion-trapping capability, signal intensity, mass range and some other properties of the ion trap. For a quadrupole ion trap built with ideal hyperbolic electrodes, its effective electric field radius can be obtained by its geometrical size, while it is very difficult to obtain the effective electric field radius for a non-hyperbolic ion trap. In this study, the effective electric field radius of a linear ion trap and some ceramic rectilinear ion traps (cRITs) were investigated via the digital ion trap technology. The dipole frequency of supplementary AC for excitation was locked at a certain value of the main RF trapping wave, and the characteristic q values for excitation could be determined accordingly. The q values could be further used to calculate the effective electric field radius through theoretical calculations. A linear equation had been fitted between the q values for excitation and the square of period T2 through experiments subsequently. The relative deviation between the measured electric field radius and the simulative electric field radius is less than 2%. The simulation results and experimental validation show that the approach has predictive power for modeling and measuring the effective field radius of non-hyperbolic ion traps. It is certainly significant for further understanding the performances of non-hyperbolic quadrupole systems.

Investigation of the effect of an octopole electric field on a linear ion trap and an asymmetric semi-circular linear ion trap analyzer.

Linear ion trap mass analyzer could improve analytical performance compared to the traditional three-dimensional ion trap. In this study, a systematic investigation of the effect of octopole field on the performance of linear quadrupole ion trap was studied by both theoretical simulations and experiments. An asymmetric semi-circular linear ion trap (AsC-LIT) analyzer was designed and tested based on the theoretical results. The AsC-LIT consists of one pair of larger semi-circular rods with radius Ry and one pair of smaller semi-circular rods with radius Rx (Ry > Rx) in the cross section for introducing the quantitative octopole field. The analytical performances of these simplified AsC-LITs with different amounts of octopole fields were carefully investigated using both theoretical simulations and experimental validation. Experimental results showed that it could have a mass resolution of 1645 at m/z 175 (arginine); furthermore, the low mass cutoff and CID efficiency can be significantly improved when some positive octopole is added. The simulative results indicated that 2.56% octopole component was the best choice for achieving higher analytical performances. The theoretical and experimental studies of this work could certainly enrich the knowledge of a higher order electric field effect on the linear ion trap, furthermore, the simple geometric design and performance characteristics of this new AsC-LIT make it particularly attractive in the development of miniaturized mass spectrometers.

Direct distinction of ibuprofen and flurbiprofen enantiomers by ion mobility mass spectrometry of their ternary complexes with metal cations and cyclodextrins in the gas phase.

Enantiomeric drugs are widely used and play important roles in pharmaceuticals. Ion mobility spectrometry coupled with mass spectrometry technology provides a unique method for distinguishing the enantiomeric drugs, enantiomeric identification, and quantitation in the gas phase. In this study, enantiomeric molecules of ibuprofen and flurbiprofen were clearly recognized by forming host-guest complex ions using trapped ion mobility time-of-flight mass spectrometry. Ternary complex ions can be produced easily by electrospray ionization of the mixed solutions of ibuprofen, cyclodextrins, and CaCl2 , LiCl, or NaCl, as well as flurbiprofen, cyclodextrins, and CaCl2 . The relative contents of different chiral ibuprofens in a mixed solution were also quantitatively measured. This new method is a simple, effective, and a convenient enantioselective analysis method.

LncRNA KCNA2-AS regulates spinal astrocyte activation through STAT3 to affect postherpetic neuralgia.

OBJECTIVES: Postherpetic neuralgia (PHN) is the most common complication of herpes zoster, but the mechanism of PHN is still unclear. Activation of spinal astrocytes is involved in PHN. Our study aims to explore whether lncRNA KCNA2 antisense RNA (KCNA2-AS) regulates spinal astrocytes in PHN through signal transducers and activators of transcription 3 (STAT3). METHODS: Varicella zoster virus (VZV)-infected CV-1 cells were injected into rats to construct a PHN model. Primary spinal cord astrocytes were activated using S-Nitrosoglutathione (GSNO). Glial fibrillary acidic protein (GFAP; marker of astrocyte activation), phosphorylated STAT3 (pSTAT3), and KCNA2-AS were analyzed by immunofluorescence and RNA fluorescence in situ hybridization. RNA pull-down and RNA immunoprecipitation were used to detect binding of KCNA2-AS to pSTAT3. RESULTS: KCNA2-AS was highly expressed in the spinal cord tissue of PHN model rats, and was positively correlated with GFAP expression. GFAP was significantly increased in GSNO-induced cells, but the knockdown of KCNA2-AS reversed this result. Meanwhile, pSTAT3 was significantly increased in GSNO-induced cells, but knockdown of KCNA2-AS reduced pSTAT3 within the nucleus while the total pSTAT3 did not change significantly. pSTAT3 bound to KCNA2-AS and this binding increased with GSNO treatment. Furthermore, knockdown of KCNA2-AS in PHN model rats relieved mechanical allodynia. CONCLUSION: Down-regulation of KCNA2-AS alleviates PHN partly by reducing the translocation of pSTAT3 cytoplasm to the nucleus and then inhibiting the activation of spinal astrocytes.

Transplantation of platelet-derived mitochondria alleviates cognitive impairment and mitochondrial dysfunction in db/db mice.

Diabetes-associated cognitive impairment (DACI) can increase the risk of major cardiovascular events and death. Neuronal functionality is highly dependent on mitochondria and emerging evidence has shown that mitochondrial transplantation is a potential and effective strategy that can reduce brain injury and associated disorders. Platelets are abundant in blood and can be considered a readily available source of small-size mitochondria. These cells can be easily acquired from the peripheral blood with minimal invasion via simple venipuncture. The present study aimed to investigate whether transplantation of platelet-derived mitochondria (Mito-Plt) could improve DACI. Cognitive behaviors were assessed using the Morris water maze test in db/db mice. The results demonstrated that Mito-Plt was internalized into hippocampal neurons 24 h following intracerebroventricular injection. Importantly, one month following Mito-Plt transplantation, DACI was alleviated in db/db mice and the effect was accompanied with increased mitochondrial number, restored mitochondrial function, attenuated oxidative stress and neuronal apoptosis, as well as decreased accumulation of Aß and Tau in the hippocampus. Taken together, the data demonstrated that transplantation of Mito-Plt attenuated cognitive impairment and mitochondrial dysfunction in db/db mice. This method may be a potential therapeutic application for the treatment of DACI.

Reactions of Transition-Metal Carbyne Cations with Ethylene in the Gas Phase.

The reactions of iridium- and osmium-carbyne hydride cations [HIrCH]+ and [HOsCH]+ with ethylene have been studied using mass spectrometry with isotopic-labeling in the gas phase. The carbyne reactivity is compared with that of the rhodium, cobalt, and iron analogues [TMCH2]+ (TM = Fe, Co, and Rh), which were determined to have the carbene structures. Besides the cycloaddition/dehydrogenation reaction in forming the [TMC3H4]+ + H2 (TM = Ir and Os) products, a second reaction pathway producing the [TMC2H2]+ ion and CH4 via triple hydrogen atom transfer reactions to the carbyne carbon is observed to be the major channel. The latter channel is not observed in the rhodium, cobalt, and iron carbene cation reactions. Quantum-chemical calculations indicate that the distinct reactivity is not due to different initial structures of the reactants. Both reaction channels are predicted to be thermodynamically exothermic and kinetically facile for the carbyne cations, and the reactions proceed with the initial formation of a carbene intermediate via hydride-carbyne coupling. The latter channel is also exothermic but kinetically unfavorable for the rhodium, cobalt, and iron carbene cations.

Linear ion trap mass selectivity with impulse power supply and sinusoidal dipolar excitation.

RATIONALE: An ion trap mass analyzer can be operated by either a sinusoidal waveform power supply or an impulse waveform power supply. The optimal conditions for the performance of ion trap which is driven by an impulse waveform power supply with sinusoidal dipolar voltage were investigated theoretically, and further verified by experiments. METHODS: The analytical relationship between ß and q values is derived theoretically for optimal performance, and the dependencies ß(q) for different trapezoidal waveforms are studied. To explain the dependence of resolution with working point q, the derivative dß/dq is also derived analytically for the case of a rectangular waveform power supply. The theoretical results are further verified by experiments. RESULTS: The results from both theoretical calculations and experiments are in very good agreement. The behaviour resolution with q is controlled by the dispersion dß/dq that was also confirmed by experiments, when the resolution increases with q. CONCLUSIONS: The optimal conditions of ß, qex values and required excitation time n are when S(q) is close to 1 for an ion trap driven by trapezoidal waveform voltage with sinusoidal dipolar voltage. It shown that with increasing impulse parameter τ the dispersion dß/dq decreases and the mass resolution also decreases as result. In the case of applying a rectangular waveform shape voltage, the mass selectivity is the same as for the sinusoidal wave shape. Copyright © 2016 John Wiley & Sons, Ltd.

Enhancement of Ion Activation and Collision-Induced Dissociation by Simultaneous Dipolar Excitation of Ions in x- and y-Directions in a Linear Ion Trap.

Collision-induced dissociation (CID) in linear ion traps is usually performed by applying a dipolar alternating current (AC) signal to one pair of electrodes, which results in ion excitation mainly in one direction. In this paper, we report simulation and experimental studies of the ion excitation in two coordinate directions by applying identical dipolar AC signals to two pairs of electrodes simultaneously. Theoretical analysis and simulation results demonstrate that the ion kinetic energy is higher than that using the conventional CID method. Experimental results show that more activation energy (as determined by the intensity ratio of the a4/b4 fragments from the CID of protonated leucine enkephalin) can be deposited into parent ions in this method. The dissociation rate constant in this method was about 3.8 times higher than that in the conventional method under the same experimental condition, at the Mathieu parameter qu (where u = x, y) value of 0.25. The ion fragmentation efficiency is also significantly improved. Compared with the conventional method, the smaller qu value can be used in this method to obtain the same internal energy deposited into ions. Consequently, the "low mass cut-off" is redeemed and more fragment ions can be detected. This excitation method can be implemented easily without changing any experimental parameters.

A novel asymmetrical arc-shaped electrode ion trap for improving the performance of a miniature mass spectrometer.

RATIONALE: The pivotal challenge associated with miniature mass analyzers is their proper design and construction without sacrificing performance. In order to analyze and improve the performance of a miniature linear ion trap with odd and even multipole fields, we designed a novel asymmetrical arc-shaped electrode ion trap (AAEIT), and tested the properties of AAEITs with different dimensions. METHODS: A series of asymmetrical ion traps using arc-shaped electrodes were designed to optimize the properties (resolutions and intensity) of the coupling effects between odd and even multipole fields. Using arginine and reserpine, we evaluated the performance of mass resolution, ion intensity ratio and deduced the collision-induced dissociation (CID) efficiency using a self-constructed electrospray ionization mass spectrometry (ESI-MS) platform. RESULTS: An AAEIT with field radius dimensions of 5 mm × 5.75 mm exhibits a good performance: its maximum resolution of 833 (FWHM) at m/z 175 was achieved for the side of small electrode. With this AAEIT, a tandem mass (MS/MS) capability with 91.0% CID efficiency was obtained with reserpine (m/z 609). CONCLUSIONS: The results indicated that the AAEIT, comprising both odd and even multipole fields, could act as a qualified linear ion trap mass analyzer with compact structure, high resolution, and high tandem mass analysis efficiency. It has a great potential in miniature mass spectrometry.

Development of dual-photoionization ion trap mass spectrometry and its application for direct analysis of VOCs in fruit aroma.

Photoionization-ion trap mass spectrometry (PI-ITMS) is one of the major directions of mass spectrometer miniaturization because of its great potential for rapid on-site VOCs detection in many cases. Traditionally, PI has always been investigated separately and is restrained by ion transmission structure, so a new structure needs to be designed and investigated for simplifying and improving the ion transmission efficiency. Interestingly, our preliminary experiments found that the signal intensity and mass range can be effectively improved by combing atmospheric pressure photoionization (APPI) and low-pressure photoionization (LPPI). Therefore, in this paper, a new dual photoionization - ion trap mass spectrometry (DPI-ITMS) was developed, explored and used to directly analyze complex VOCs. Compared with traditional single PI configuration, it presents two obvious merits: (1) simplified ion transmission structure, eliminating the need to use deflection electrode to repel ions and avoiding breakdown risk. (2) some missing/weak low m/z ion mass spectral peaks in APPI and some high m/z ion mass spectral peaks in LPPI were improved in DPI detection mode. In addition, by combining multivariate statistical analysis, we preliminary achieved in differentiating fruit types and maturity level. In summary, we concluded that the developed DPI-ITMS has moderate detection sensitivity (limited by the homemade ITMS, 0.1-1 ppmv with RSD of 6.36 %), and the DPI-ITMS configuration can be referenced by future PI-MS, and this study also provides a high-throughput, simple, noninvasive and no chemical contamination solution for analyzing main VOCs in fruit aroma.

Dipolar direct current driven collision-induced dissociation in a digital ceramic-based rectilinear ion trap mass spectrometer.

A digital ion trap (DIT) and rectilinear ion trap (RIT) have been proven to be very useful technology in the past years. In this work, the digital ion trap technology was combined with the ceramic-based rectilinear ion trap (cRIT) system. The rectangular waveform was used for ion trapping. A dipolar excitation waveform which was formed by dividing down the trapping rectangular waveform was used for the ion ejection. We found that the high efficient collision-induced dissociation (CID) procedure could be obtained by simply manipulating the duty cycle of the dipole excitation waveform, and it could significantly simplify the tandem mass spectrometry analysis method and procedure with an ion trap, since the dipolar direct current (dc) voltage could be easily produced and applied to one of the pair of electrodes, which was fully controlled by the computer software and does not need any hardware modification.

Printed circuit board ion trap mass analyzer: its structure and performance.

An ion trap (IT) mass analyzer can be simply built with low cost material-the printed circuit board (PCB). A printed circuit board ion trap (PCBIT) can perform ion trapping, mass analysis, and tandem mass spectrometry as a conventional ion trap mass analyzer. In a PCBIT, each PCB electrode was fabricated to specially designed patterns with several separate electric strips. The strips' electrodes were insulated from each other and applied with different voltages during the experiment. Therefore, the electric field distribution inside the ion trap region may be adjusted and optimized by simply adjusting the voltage on each strip. The performance of the PCBIT can also be optimized since the property of an ion trap is strongly dependent on the field distribution. The fabrication, operation, and performance of the PCBIT are described and characterized in this paper. A prototype PCBIT was built with two pairs of 64 mm × 12 mm PCB rectangular plates and one pair of 10 mm × 10 mm stainless steel square plates. A mass analysis with a resolving power of over 1500 and a mass range of around 3000 Th was observed. The mass-selected isolation and collision-induced dissociation (CID) of ions were also tested using the homemade PCBIT system. The adjustable electric field distribution, simple structure, and low cost of PCBIT make it certainly suitable for the further miniaturization of the portable mass spectrometer.