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Membrane-extraction ion mobility spectrometry (ME-IMS) has been developed for in situ sampling and analysis of trace chlorinated hydrocarbons in water in a single procedure. The sampling is configured so that aqueous contaminants permeate through a spiral hollow poly(dimethylsiloxane) (PDMS) membrane and are carded away by a vapor flow through the membrane tube. The extracted analyte flows into an atmospheric-pressure chemical-ionization (APCI) chamber and is analyzed in a specially made IMS analyzer. The PDMS membrane was found to effectively extract chlorinated hydrocarbon solvents from the liquid phase to vapor. The specialized IMS analyzer has measured resolutions of R = 33 and 41, respectively, for negative-and positive-modes and is capable of detecting aqueous tetrachloroethylene (PCE) and trichloroethylene (ICE) as low as 80 and 74 [micro]g/L in the negative ion mode, respectively. The time-dependent characteristics of sampling and detection of TCE are both experimentally and theoretically studied for various concentrations, membrane lengths, and flow rates. These characteristics demonstrate that membrane-extraction IMS is feasible for the continuous monitoring of chlorinated hydrocarbons in water. 10.1021/ac100162d

A new atmospheric pressure air direct current glow discharge (DCGD) ionization source has been developed for ion mobility spectrometry (IMS) to overcome the regularity problems associated with the conventional [sup.63]Ni source and the instability of the negative corona discharge. Its general electrical characteristics were experimentally investigated. By equipping it to IMS, a higher sensitivity was obtained compared to that of a [sup.63]Ni source and corona discharge, and a linear dynamic range from 20 ppb to 20 ppm was obtained for m-xylene. Primary investigations showed that alkanes, such as pentane, which are nondetectable or insensitively detectable with [sup.36]Ni-IMS, can be efficiently detected by DCGD-IMS and the detection limit of 10 ppb can be reached. The preliminary results have shown that the new DCGD ionization source has great potential applications in IMS, such as online monitoring of environment pollutants and halogenated compounds.

The energy-dependent unimolecular dissociation rate k(E) of metastable CH3CO radical species has been measured with a newly developed method. The technique involves the use of subpicosecond time-clocked photofragment imaging to observe the decay of the CH3CO radicals formed by ultraviolet photodissociation of CH3COl. The radicals with different internal energies were dispersed in space by the recoil velocities. The decay rates were measured for each internal energy. The results were compared with those obtained by Rice-Ramsperger-Kassel-Marcus calculations.

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]

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]

The ion conversion processes in CH 2 Cl 2 -enhanced vacuum ultraviolet photoionization of oxygenated volatile organic compounds (OVOCs) have been systematically studied by regulating the pressure, humidity, and reaction time in the ionization source of a time-of-flight mass spectrometer. As the ionization source pressure increased from 100 to 1100 Pa, the main characteristic ions changed from CH 2 Cl + to CH 2 Cl + (H 2 O), CH 2 OH + , and C 2 H 4 OH + and then to the hydrated hydronium ions H 3 O + (H 2 O) n ( n = 1, 2, 3). The total ion current (TIC) almost remained unchanged even if the humidity increased from 44 to 3120 ppmv, indicating interconversion between ions through ion-molecule reactions. The intensity of protonated methanol/ethanol (sample S) ion was almost linearly correlated with the intensity of H 3 O + (H 2 O) n , which pointed to the proton transfer reaction (PTR) mechanism. The reaction time was regulated by the electric field strength in the ionization region. The intensity variation trends of different ions with the reaction time indicated that a series of step-by-step ion-molecule reactions occurred in the ionization source, i.e., the primary ion CH 2 Cl + reacted with H 2 O and converted to the intermediate product ions CH 2 OH + and C 2 H 4 OH + , which then further reacted with H 2 O and led to the production of H 3 O + , and finally, the protonated sample ion SH + was obtained through PTR with H 3 O + , as the ion-molecule reactions progressed. This study provides valuable insights into understanding the formation mechanism of some unexpected intermediate product ions and hydrated hydronium ions in dopant-enhanced VUV photoionization and also helps to optimize experimental conditions to enhance the sensitivity of OVOCs.

Hydrogen cyanide (HCN) is a well-known toxic compound in many fields. The trace amount of endogenous HCN in human exhalation has been associated with the presence of Pseudomonas aeruginosa (PA) infection in cystic fibrosis (CF) patients. Online monitoring of HCN profile is promising to screen PA infection rapidly and accurately. In this study, a gas flow-assisted negative photoionization (NPI) mass spectrometry method was developed for monitoring the single-exhalation HCN profile. The sensitivity could be optimized by introducing helium to eliminate the humidity influence and reduce the low mass cutoff effect, with improvements of a factor 150 observed. By employing a purging gas procedure and minimizing the length of the sample line, the residual and response time were greatly reduced. The limit of detection (LOD) of 0.3 ppbv and time resolution of 0.5 s were achieved. HCN profiles of exhalations from different volunteers before or after gargling with water were detected to show the performance of the method. All profiles showed a sharp peak and a stable end-tidal plateau, representing the concentration of oral cavity and end-tidal gas, respectively. The HCN concentration based on the plateau of the profile showed better reproducibility and accuracy, which indicates this method has potential application in the detection of PA infection in CF patients.

High-quality InP-based quantum dots (QDs) have become very promising, environmentally benign light emitters for display applications, but their synthesis generally entails hazardous hydrofluoric acid. Here, we present a highly facile route to InP/ZnSe/ZnS core/shell/shell QDs with a near-unity photoluminescence quantum yield. As the key additive, the inorganic salt ZnF 2 mildly reacts with carboxylic acid at a high temperature and in situ generates HF, which eliminates surface oxide impurities, thus facilitating epitaxial shell growth. The resulting InP/ZnSe/ZnS QDs exhibit a narrower emission line width and better thermal stability in comparison with QDs synthesized with hydrofluoric acid. Light-emitting diodes using large-sized InP/ZnSe/ZnS QDs without replacing original ligands achieve the highest peak external quantum efficiency of 22.2%, to the best of our knowledge, along with a maximum brightness of >110 000 cd/m 2 and a T 95 lifetime of >32 000 h at 100 cd/m 2 . This safe approach is anticipated to be applied for a wide range of III-V QDs.

Discontinuous atmospheric pressure interface (DAPI) consisting of a pinch valve, a silicone tube, and two metal capillaries has been widely used in miniature mass spectrometry. It is interesting that clear ion signals could be observed even when the extra ionization source was turned off. In-depth analysis suggested that this new ionization phenomenon known as triboionization is based on the surface friction on the inner surface of the silicone tube during the on/off of the pinch valve. In this study, triboionization in the DAPI of a miniature ion trap mass spectrometer was investigated. It was discovered that the signal intensity depended greatly on the material and the roughness of the silicone tube used in the DAPI. By rubbing the inner surface of the silicone tube, for example, the signal intensity can increase by nearly 20 times. Two connected pinch valves were developed to study the effects of the discharge pressure, the number, and the frequency of on/off of the pinch valve on triboionization, which were verified to have a large impact on the product ions. In addition, the humidity of the inner surface of the silicone tube impacted the signal intensity of product ions and the mass spectrum patterns, where the product ions were typically protonated ions. As the humidity increases, the signal intensity of analytes with high proton affinity increases accordingly. This triboionization source, which does not require heat, light, radiation, auxiliary gas, or solution, has been preliminarily proved to have potential for surface detection after continuous enrichment.

Hazardous chemical leakages involved in chemical terrorist attacks and chemical industrial accidents have been posing severe threats to human health and the environment. Vehicle-mounted mass spectrometry (MS) has been developed for continuous, on-road measurements to map the spatial and temporal distributions of hazardous chemicals. However, the detection of chemicals with small temporal scales and spatial scales is always challenging. In this study, a parallel coupling apparatus combining the techniques of ion mobility spectrometry and ion trap MS ( p -IMS-ITMS) was developed to improve the detection rate and the time response capability of a stand-alone ITMS system for short time-span chemical tracking. A workflow was also proposed along with the apparatus, where the ITMS system can be triggered, as chemical suspects were discovered with the IMS system. The sampling positions of the ITMS system were investigated and optimized. In addition, a strategy was proposed to diminish the time span of samples from 1.5 to 0.5 s for evaluating the performances of the p -IMS-ITMS system. The detection rate of the stand-alone ITMS system was measured to be only 9.5, 32, and 87.5% for the time span of 0.5, 1, and 1.5 s, respectively. By comparison, the detection rates of the p -IMS-ITMS system were 99.5, 100, and 100%, where the detection rate was increased by a factor of 10 for 0.5 s time span. Moreover, the addition of an IMS system could provide temporal patterns of hazardous chemicals with a resolution of 33 ms. Finally, the potential of the p -IMS-ITMS system for environmental navigation monitoring and assessment was further demonstrated by detecting the leakages of dimethyl methyl phosphonate and dipropylene glycol monomethyl ether.

Online monitoring of exhaled propofol concentration is important for anesthetists to provide adequate anesthesia as propofol concentrations in plasma and breath are correlated reasonably well. Exhaled propofol could be detected by 63 Ni ion mobility spectrometry in negative ion mode; however, the radioactivity of 63 Ni source restricts its clinical application due to safety, environmental, and regulatory concerns. An acetone-assisted negative photoionization ion mobility spectrometer (AANP-IMS) using a side-mounted vacuum ultraviolet (VUV) lamp in the unidirectional (UD) flow mode was developed for sensitive measurement of exhaled propofol by producing a high percentage of O 2 - (H 2 O) n . An adsorption sampling and time-resolved purge introduction system was developed to eliminate the interference of residual inhaled anesthetic sevoflurane based on their different adsorptions between propofol and sevoflurane on the inwall of the fluorinated ethylene propylene (FEP) sample loop. The effects of the inner diameter and the length of the sample loop on the signal intensity of propofol and the time-resolution between propofol and sevoflurane were theoretically and experimentally investigated. A sample loop with 3 mm i.d. and 150 cm length allowed sensitive measurement of exhaled propofol with a response time of 4 s, a linear response range for propofol was achieved to be 0.2 to 14 ppbv with a limit of detection (LOD) of 60 pptv, and the quantification of propofol was not influenced by the change of the sevoflurane concentration. Finally, the performance of monitoring exhaled propofol during surgery was demonstrated on a patient undergoing laparoscopic distal pancreatectomy combined with cholecystectomy.

Direct mass spectrometric measurements of saturated hydrocarbons, especially small n-alkanes, remains a great challenge because of low basicity and lack of ionizable functional groups. In this work, a novel high-pressure photoelectron-induced O 2 + cation chemical ionization source (HPPI-OCI) at kPa based on a 10.6 eV krypton lamp was developed for a time-of-flight mass spectrometer (TOFMS). High-intensity O 2 + reactant ions were generated by photoelectron ionization of air molecules in the double electric field ionization region. The quasi-molecular ions, [M-H] + , of C3-C6 n-alkanes, gradually dominated in the mass spectra when the ion source pressure was elevated from 88 to 1080 Pa, with more than 3 orders of magnitude improvement in signal intensity. As a result, the achieved limits of detection were lowered to 0.14, 0.11, 0.07, and 0.1 ppbv for propane, n-butane, n-pentane, and n-hexane, respectively. The performance of the HPPI-OCI TOFMS was first demonstrated by analysis of exhaled small n-alkanes from healthy smokers and nonsmokers. Then the concentration variations of exhaled small n-alkanes of four healthy volunteers were analyzed after alcohol consumption to explore the alcohol-hepatoxicity-related oxidative stress. In summary, this work provides new insights for controlling the O 2 + -participating chemical ionization by adjusting the ion source pressure and develops a novel direct mass spectrometric method for sensitive measurements of mall n-alkanes.

Ammonia synthesis is the single most important chemical process in industry and has used the successful heterogeneous Haber-Bosch catalyst for over 100 years and requires processing under both high temperature (300-500 °C) and pressure (200-300 atm); thus, it has huge energy costs accounting for about 1-3% of human's energy consumption. Therefore, there has been a long and vigorous exploration to find a milder alternative process. Here, we demonstrate that by using an iron- and graphene-based catalyst, Fe@3DGraphene, hot (ejected) electrons from this composite catalyst induced by visible light in a wide range of wavelength up to red could efficiently facilitate the activation of N 2 and generate ammonia with H 2 directly at ambient pressure using light (including simulated sun light) illumination directly. No external voltage or electrochemical or any other agent is needed. The production rate increases with increasing light frequency under the same power and with increasing power under the same frequency. The mechanism is confirmed by the detection of the intermediate N 2 H 4 and also with a measured apparent activation energy only ∼1/4 of the iron based Haber-Bosch catalyst. Combined with the morphology control using alumina as the structural promoter, the catalyst retains its activity in a 50 h test.

Photon ionization mass spectrometry (PI-MS) is a widely used technique for the online detection of trace substances in complex matrices. In this work, a new high-pressure photon ionization (HPPI) ion source based on a vacuum ultraviolet (VUV) Kr lamp was developed for time-of-flight mass spectrometry (TOFMS). The detection sensitivity was improved by elevating the ion source pressure to about 700 Pa. A radio frequency (RF)-only quadrupole was employed as the ion guide system following the HPPI source to achieve high ion transmission efficiency. In-source collision induced dissociation (CID) was conducted for accurate chemical identification by varying the voltage between the ion source and the ion guide. The high humidity of the breath air can promote the detection of some compounds with higher ionization potentials (IPs) that could not be well detected by single photon ionization (SPI) at low pressure. Under 100% relative humidity (37 °C), the limits of detection down to 0.015 ppbv (parts per billion by volume) for aliphatic and aromatic hydrocarbons were obtained. This HPPI-TOFMS system was preliminarily applied for online investigations of the exhaled breath from both healthy nonsmoker and smoker subjects, demonstrating its analytical capacity for complicated gases analysis. Subsequently, several frequently reported VOCs in the breath of healthy volunteers, i.e., acetone, isoprene, 2-butanone, ethanol, acetic acid, and isopropanol, were successfully identified and quantified.

Peroxide explosives, such as triacetone triperoxide (TATP) and hexamethylene trioxide diamine (HMTD), were often used in the terrorist attacks due to their easy synthesis from readily starting materials. Therefore, an on-site detection method for TATP and HMTD is urgently needed. Herein, we developed a stand-alone dopant-assisted positive photoionization ion mobility spectrometry (DAPP-IMS) coupled with time-resolved thermal desorption introduction for rapid and sensitive detection of TATP and HMTD in complex matrices, such as white solids, soft drinks, and cosmetics. Acetone was chosen as the optimal dopant for better separation between reactant ion peaks and product ion peaks as well as higher sensitivity, and the limits of detection (LODs) of TATP and HMTD standard samples were 23.3 and 0.2 ng, respectively. Explosives on the sampling swab were thermally desorbed and carried into the ionization region dynamically within 10 s, and the maximum released concentration of TATP or HMTD could be time-resolved from the matrix interference owing to the different volatility. Furthermore, with the combination of the fast response thermal desorber (within 0.8 s) and the quick data acquisition software to DAPP-IMS, two-dimensional data related to drift time (TATP: 6.98 ms, K0 = 2.05 cm(2) V(-1) s(-1); HMTD: 9.36 ms, K0 = 1.53 cm(2) V(-1) s(-1)) and desorption time was obtained for TATP and HMTD, which is beneficial for their identification in complex matrices.

Bradbury-Nielsen gate (BNG) is commonly used in ion mobility spectrometers. It, however, transmits only a small fraction of the ions into the drift region, typically 1%. In contrast, all ions in the ionization chamber could be efficiently compressed into the drift region by the field switching gate (FSG). We report in this paper on the simultaneous use of BNG and field switching (FS) to enhance ion utilization of the BNG. In this technique, the FS collects the ions existing in the region between the FS electrode and the BNG and drives them quickly, going through the BNG in the period of gate opening. The BNG acts as the retarding field in the reported FSG to stop ions from diffusing into the drift region in the period of gate closing. Using this technique, an increase of at least 10-fold in the ion peak height without any loss of resolution is achieved for acetone compared with the BNG-only approach at a gate pulse width of 150 μs, and an even larger improvement factor of 21 is achieved for heavier DMMP dimer ions. This technique can be adapted to the current BNG-based ion mobility instruments to significantly enhance their sensitivity without any modification of the drift tube hardware.

Single-photon ionization mass spectrometry (SPI-MS) is a versatile and powerful analytical technique for online and real-time analysis of organic species; however, it is confronted with an intrinsic drawback of lacking structural information on the investigated molecules, let alone differentiation of isobaric compounds. In this work, we describe a first attempt to integrate in-source collision-induced dissociation (CID) to the SPI ion source in a SPI-MS instrument. The in-source CID was accomplished by elevating the pressure in the ion source to medium vacuum pressure (MVP) and raising the extraction voltage. With the aid of in-source CID, both the SPI-induced molecular ion and CID-generated fragment ion mass spectra can be obtained to endue each analyte with its unique spectrometric "fingerprint". The capability for differentiation of isobaric compounds is demonstrated by analyzing two groups of isobaric compounds with molecular weights of 72 and 106 Da, respectively, and quantitative analysis of p-xylene and ethylbenzene in gas mixture. As a result, isobaric compounds with different characteristic fragment ions or appearance energies can be successfully distinguished. The work presents a feasible method for practical applications of SPI-MS to differentiate isobaric compounds conveniently and rapidly without MS/MS technique or coupling additional separation technologies.

With respect to massive consumption of ammonia and rigorous industrial synthesis conditions, many studies have been devoted to investigating more environmentally benign catalysts for ammonia synthesis under moderate conditions. However, traditional methods for analysis of synthesized ammonia (e.g., off-line ion chromatography (IC) and chemical titration) suffer from poor sensitivity, low time resolution, and sample manipulations. In this work, charge-transfer ionization (CTI) with O2(+) as the reagent ion based on a vacuum ultraviolet (VUV) lamp in a time-of-flight mass spectrometer (CTI-TOFMS) has been applied for real-time monitoring of the ammonia synthesis in a microreactor. For the necessity of long-term stable monitoring, a self-adjustment algorithm for stabilizing O2(+) ion intensity was developed to automatically compensate the attenuation of the O2(+) ion yield in the ion source as a result of the oxidation of the photoelectric electrode and contamination on the MgF2 window of the VUV lamp. A wide linear calibration curve in the concentration range of 0.2-1000 ppmv with a correlation coefficient (R(2)) of 0.9986 was achieved, and the limit of quantification (LOQ) for NH3 was in ppbv. Microcatalytic synthesis of ammonia with three catalysts prepared by transition-metal/carbon nanotubes was tested, and the rapid changes of NH3 conversion rates with the reaction temperatures were quantitatively measured with a time resolution of 30 s. The high-time-resolution CTI-TOFMS could not only achieve the equilibrium conversion rates of NH3 rapidly but also monitor the activity variations with respect to investigated catalysts during ammonia synthesis reactions.

Ion mobility spectrometry (IMS) has become the most deployed technique for on-site detection of trace explosives, and the reactant ions generated in the ionization source are tightly related to the performances of IMS. Combination of multiform reactant ions would provide more information and is in favor of correct identification of explosives. Fast switchable CO3(-)(H2O)n and O2(-)(H2O)n reactant ions were realized in a dopant-assisted negative photoionization ion mobility spectrometer (DANP-IMS). The switching could be achieved in less than 2 s by simply changing the gas flow direction. Up to 88% of the total reactant ions were CO3(-)(H2O)n in the bidirectional mode, and 89% of that were O2(-)(H2O)n in the unidirectional mode. The characteristics of combination of CO3(-)(H2O)n and O2(-)(H2O)n were demonstrated by the detection of explosives, including 2,4,6-trinitrotoluene (TNT), cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), ammonium nitrate fuel oil (ANFO), and black powder (BP). For TNT, RDX, and BP, product ions with different reduced mobility values (K0) were observed with CO3(-)(H2O)n and O2(-)(H2O)n, respectively, which is a benefit for the accurate identification. For ANFO, the same product ions with K0 of 2.07 cm(2) V(-1) s(-1) were generated, but improved peak-to-peak resolution as well as sensitivity were achieved with CO3(-)(H2O)n. Moreover, an improved peak-to-peak resolution was also obtained for BP with CO3(-)(H2O)n, while the better sensitivity was obtained with O2(-)(H2O)n.