Single Photon Ionization Mass Spectrometry Research Articles

Investigation of pyruvic acid photolysis at the air-liquid interface as a source of aqueous secondary organic aerosols

Pyruvic acid (PA) is a ubiquitous 2-oxocarboxylic acid in the atmosphere. Its photochemical process at the air-liquid (a-l) interface has been suggested as an important source of aqueous secondary organic aerosols. We investigated the photochemical reaction pathways of PA at the a-l interface using synchrotron-based vacuum ultraviolet single-photon ionization mass spectrometry (VUV SPI-MS) coupled with the System for Analysis at the Liquid Vacuum Interface (SALVI) microreactor. Results from mass spectral analysis and the determination of appearance energies (AEs) indicate that photolysis of PA can generate radicals, then they recombine with carboxylic acids and simple molecular oligomers. Furthermore, the preliminary products could form larger oligomers via radical reaction or esterification in the presence of hydroxyl and carboxyl functional groups. Mass spectral comparison shows that most photochemical reactions would complete within 4 h. The expanded photochemistry-driven reaction flowchart of PA is proposed based on the newly discovered products. Our results reveal that the interfacial PA photochemical reactions have different mechanisms from the bulk liquid due to the interfacial properties, such as molecular density, composition, and ion concentration. Our findings show that in situ mass spectral analysis with bright photon ionization is useful to elucidate the contribution of a-l interfacial reactions leading to aqSOA formation.

Traceability tagging of volatile organic compound sources and their contributions to ozone formation in Suzhou using vehicle-based portable single-photon ionization mass spectrometry

BackgroundIn recent decades, there has been an increasing global preoccupation with atmospheric volatile organic compounds (VOCs). Given the significant impact of VOCs as pollutants and essential precursors of ozone (O3) in urban and industrial areas, it is imperative to identify and quantify the sources of their emissions to facilitate the development and implementation of effective environmental control strategies.MethodsA mobile laboratory vehicle equipped with a single-photon ionization–time-of-flight mass spectrometer (SPI–TOFMS) and a navigation system was employed to establish the traceability of VOCs that contribute to the formation of ozone in Suzhou Industrial Park. The method exhibited a favorable detection limit of 0.090 ppbv, accompanied by a mass resolution of 1500 for the instrument and a correlation coefficient ≥ 0.990. A positive matrix factorization (PMF) model was utilized to determine the source appointment of the VOCs.ResultsThe study tentatively traced and identified the VOCs emissions source and their contribution to ozone formation in Suzhou. Using the PMF model, the sources of VOCs were profiled: three primary sources of VOCs were identified, namely, vehicular emissions, an industrial solvent, and biofuel combustion. Alkanes groups were found to be the most abundant VOCs species, accounting for 60% of the total VOCs, followed by aromatics and alkenes. Maximum incremental reactivity (MIR) quantifies the impact of photochemical reaction mechanism on the potential ozone formation.ConclusionsThe findings of this study complement existing knowledge on the pollution status of atmospheric VOCs and highlight the correlation with ozone formation potential in Suzhou. The aforementioned sources were identified as the primary factors responsible for the pollution in Suzhou. The successful implementation of SPI–TOFMS has demonstrated a promising methodology that is well-suited for the real-time and online monitoring of VOCs in the atmosphere. In addition, a library for identifying VOC fingerprints from the same plant was established. This library serves as a comprehensive resource for establishing on-site VOC traceability, estimating source apportionment, and evaluating their impact on ozone formation.

Unconventional Pathway in the Gas‐Phase Synthesis of 9H‐Fluorene (C13H10) via the Radical–Radical Reaction of Benzyl (C7H7) with Phenyl (C6H5)

AbstractThe simplest polycyclic aromatic hydrocarbon (PAH) carrying a five‐membered ring—9H‐fluorene (C13H10)—is produced isomer‐specifically in the gas phase by reacting benzyl (C7H7⋅) with phenyl (C6H5⋅) radicals in a pyrolytic reactor coupled with single photon ionization mass spectrometry. The unconventional mechanism of reaction is supported by theoretical calculations, which first produces diphenylmethane and unexpected 1‐(6‐methylenecyclohexa‐2,4‐dienyl)benzene intermediates (C13H12) accessed via addition of the phenyl radical to the ortho position of the benzyl radical. These findings offer convincing evidence for molecular mass growth processes defying conventional wisdom that radical‐radical reactions are initiated through recombination at their radical centers. The structure of 9H‐fluorene acts as a molecular building block for complex curved nanostructures like fullerenes and nanobowls providing fundamental insights into the hydrocarbon evolution in high temperature settings.

Unconventional Pathway in the Gas-Phase Synthesis of 9H-Fluorene (C13H10) via the Radical - Radical Reaction of Benzyl (C7H7) with Phenyl (C6H5).

The simplest polycyclic aromatic hydrocarbon (PAH) carrying a five-membered ring - 9H-fluorene (C13H10) - is produced isomer-specifically in the gas phase by reacting benzyl (C7H7•) with phenyl (C6H5•) radicals in a pyrolytic reac-tor coupled with single photon ionization mass spectrometry. The unconventional mechanism of reaction is supported by theoretical calculations, which first produces diphenyl-methane and unexpectedly 1-(6-methylenecyclohexa-2,4-dienyl)benzene intermediates (C13H12) accessed via addition of the phenyl radical to the ortho position of the benzyl radical. These findings offer convincing evidence for molecular mass growth processes defying conventional wisdom that radical-radical reactions are initiated through recombination at their radical centers. The structure of 9H-fluorene acts as a molecular building block for complex curved nanostructures like fullerenes and nanobowls providing fundamental insights into the hydrocarbon evolution in high temperature settings.

An ultrasensitive SPI/PAI ion source based on a high-flux VUV lamp and its applications for the online mass spectrometric detection of sub-pptv sulfur ethers

Single-photon ionization mass spectrometry (SPI-MS) is an attractive analytical technique for the online detection of volatile organic compounds; however, the low photon flux of the vacuum ultraviolet (VUV) lamp commonly used in the SPI ion source and the corresponding low detection sensitivity remain a constraint to its wide field applications. In this study, a new VUV lamp-based SPI ion source was developed. By increasing the discharging volume and optimizing the configuration of the lens and ionizer, the photon flux of the VUV lamp and the sensitivity of the ion source were significantly improved. The VUV lamp output was 2.8 × 1015 photons s−1, which was focused into the small ionization zone, and the ion intensity of gaseous benzene under SPI achieved 1.7 × 104 counts per second per pptv (cps pptv−1). This ion source can also function in photoinduced associative ionization (PAI) mode by introducing gaseous CH2Cl2 to initiate an associative ionization reaction. Because of the high efficiency of the ion source, the amount of doped CH2Cl2 needed for PAI was greatly reduced (∼2.5% of that used in previous experiments). PAI exhibited an outstanding protonation effect on monosulfur ethers (CnH2n+1S). The signal intensities of the protonated molecular ions (MH+) were 46–128 times higher than those of the molecular ions (M+) produced by SPI. Since monosulfur ethers generally have lower SPI cross-sections than polysulfur ethers (CnH2n+1S2 or CnH2n+1S3), the PAI and SPI modes were selected for the online measurement of a series of mono- and polysulfur ethers, respectively. The obtained detection sensitivity of the mono- and polysulfur ethers reached 476.5 ± 1.72–2835.1 ± 99.5 and 47.9 ± 0.4–105.1 ± 2.3 counts pptv−1, respectively, in 10 s of sampling time. The corresponding 3σ limits of detection (LODs) were 0.12–0.71 and 0.06–0.14 pptv, respectively. This study provides advances in the development of a high-flux VUV lamp and a highly efficient SPI/PAI ion source, as well as an ultrasensitive analytical method for detecting sulfur ethers.

Studying Interfacial Dark Reactions of Glyoxal and Hydrogen Peroxide Using Vacuum Ultraviolet Single Photon Ionization Mass Spectrometry

Aqueous secondary organic aerosol (aqSOA) formation from volatile and semivolatile organic compounds at the air–liquid interface is considered as an important source of fine particles in the atmosphere. However, due to the lack of in situ detecting techniques, the detailed interfacial reaction mechanism and dynamics still remain uncertain. In this study, synchrotron-based vacuum ultraviolet single-photon ionization mass spectrometry (VUV SPI-MS) was coupled with the System for Analysis at the Liquid Vacuum Interface (SALVI) to investigate glyoxal dark oxidation products at the aqueous surface. Mass spectral analysis and determination of appearance energies (AEs) suggest that the main products of glyoxal dark interfacial aging are carboxylic acid related oligomers. Furthermore, the VUV SPI-MS results were compared and validated against those of in situ liquid time-of-flight secondary ion mass spectrometry (ToF-SIMS). The reaction mechanisms of the dark glyoxal interfacial oxidation, obtained using two different approaches, indicate that differences in ionization and instrument operation principles could contribute to their abilities to detect different oligomers. Therefore, the mechanistic differences revealed between the VUV SPI-MS and ToF-SIMS indicate that more in situ and real-time techniques are needed to investigate the contribution of the air–liquid interfacial reactions leading to aqSOA formation.

Atmospheric Pressure Single Photon Laser Ionization (APSPLI) Mass Spectrometry Using a 157 nm Fluorine Excimer Laser for Sensitive and Selective Detection of Non- to Semipolar Hydrocarbons

Atmospheric pressure single photon ionization (APSPLI) mass spectrometry utilizing a fluorine excimer laser (157 nm, 7.9 eV) is presented for the first time. For evaluation and optimization, polycyclic aromatic hydrocarbon (PAH) standard mixtures were used. The presented technique allowed for the selective ionization of semi- to nonpolar compounds in a single photon ionization process using VUV photons. Molecular radical cations were found as a base peak, whereas protonated species were almost absent. Although the ionization chamber is flushed by pure nitrogen, remaining oxygen and water traces caused unwanted oxidized ionization artifacts. Installation of water and oxygen filter cartridges significantly reduced the abundance of artifacts. For evaluating complex mixture analysis, APSPLI was applied to characterize a light crude oil. In addition to aromatic hydrocarbons, APSPLI allowed for the sensitive ionization of sulfur-containing aromatic constituents (PASH). A comparison of APSPLI to atmospheric pressure laser ionization (266 nm, 4.7 eV) revealed the additional compositional space accessible by the single photon process. APLI, conducted with UV radiation, is mainly restricted to PAH analysis. APSPLI overcomes this limitation, and PAH and PASH, which often occur simultaneously in complex mixtures, can be detected. This novel ionization concept is envisioned to have a high analytical potential further explored in the future.

New Insights into Secondary Organic Aerosol Formation at the Air-Liquid Interface.

Air-liquid interfacial processing of volatile organic compound photooxidation has been suggested as an important source of secondary organic aerosols. However, owing to the lack of techniques for studying the air-liquid interface, the detailed interfacial mechanism remains speculative. To obviate this, we enabled in situ synchrotron-based vacuum ultraviolet single photon ionization mass spectrometry using the system for analysis at the liquid-vacuum interface microreactor to study glyoxal photooxidation at the air-liquid interface. Determination of reaction intermediates and new oxidation products, including polymers and oligomers, by mass spectral analysis and appearance energy measurements has been reported for the first time. Furthermore, an expanded reaction mechanism of photooxidation and free radical induced reactions as a source of aqueous secondary organic aerosol formation is proposed. Single photon ionization can provide new insights into interfacial chemistry.

Characterization of Polyethylene Branching by Thermal Analysis-Photoionization Mass Spectrometry.

The rising demand for more and more specialized polyethylene represents a challenge for synthesis and analysis. The desired properties are dependent on the structure, but its elucidation is still intricate. For this purpose, we applied thermal analysis hyphenated to single photon ionization mass spectrometry (STA-SPI-MS). The melting and pyrolysis behavior of different types of polyethylene were tracked by DSC and mass loss. Crystallinity and melting point give hints about the branching but are also influenced by the molecular weight distribution. The evolving gas analysis patterns obtained by SPI-MS however, contain specific molecular information about the samples. Shifts in the summed spectra, which can be clearly observed with our technique, result from differently favored degradation reactions due to the respective structure. Pyrolysis gas chromatography mass spectrometry (Py-GC-EI-MS) was used to support the assignment of pyrolysis products. Principal component analysis was successfully applied to reduce the complexity of data and find suitable markers. The obtained grouping is based on the molecular fingerprint of the samples and is strongly influenced by short-chain branching. Short and medium alkenes and dienes have the strongest impact on the first four principal components. Thus, two marker ratios could be defined, which also give a comprehensible and robust grouping. Butene and pentene were the most abundant signals in our set of samples. With STA-PI-MS, a broad range of pyrolysis products can be measured at the same time, possibly extending the range for quantifiable short-chain branches to more than six carbon atoms for PE. Unfortunately, no clear trend between long-chain branching and any grouping was observed. The quite universal and soft single photon ionization enables access to many different compound classes and hence other polymers can be studied.

Assessment of Single-Photon Ionization Mass Spectrometry for Online Monitoring of in Vitro Aerosol Exposure Experiments

Chemical and physical characterization of transported evolving aerosols in an in vitro system is complex. The challenges include appropriate sampling sensitivity, measurement capabilities, and performing online measurements of constituents in the flowing aerosol during exposure. We assessed the performance of single-photon ionization mass spectrometry in measuring aerosol properties within an in vitro aerosol exposure system. The sampling efficiency of the instrument was studied under three protocols to capture the evolving aerosol process inside the exposure system, and it was evaluated using computational fluid dynamics modeling. The changes in the aerosol as dilution is applied show not only a reduction in concentration of the traced substances but also selective sampling due to evolution of the aerosol and (gas/liquid) phase partitioning of the substances forming the aerosol or a change in the aerosol properties. These effects have potentially a direct impact on the delivered dose, as aerosol deposition is dependent on particle size. Dilution affects the chemical concentration of the substances as well as the interconnected physical properties of the aerosol; therefore, the experimental design of in vitro studies should not only report the dilution flow rates but also details of the applied dilution protocol. This adds a layer of complexity to the design and comparison of studies. We also discuss the potential and limitations of single-photon ionization mass spectrometry as a tool in in vitro monitoring of aerosols.

Real time analysis of trace volatile organic compounds in ambient air: a comparison between membrane inlet single photon ionization mass spectrometry and proton transfer reaction mass spectrometry.

Real-time monitoring of volatile organic compounds (VOCs) is critical for a better understanding of chemical processes in ambient air or making minute-by-minute decisions in emergency situations. Proton transfer reaction mass spectrometry (PTR-MS) is nowadays the most commonly used technique for real-time monitoring of VOCs while membrane single photon ionization mass spectrometry (MI-SPI-MS) is a promising MS technique for online detection of trace VOCs. Here, to evaluate the potential of MI-SPI-MS as a complementary tool to PTR-MS, a comprehensive comparison has been performed between MI-SPI-MS and PTR-MS. By using two sets of standard gas mixtures TO15 and PAMS, SPI-MS shows advantages in the detection of ≥C5 alkanes, aromatics and halogens; especially for aromatics, the LODs can reach the ppt level. PTR-MS has performed better in the detection of alkenes, ketones and aldehydes. For outdoor measurements, a number of VOCs have been detected while using MI-SPI-MS and PTR-MS in parallel. Consistent temporal variations have been observed for toluene, C8-aromatics and C9-aromatics by the two instruments, with a more sensitive response from the MI-SPI-MS. Thus by measuring both standard gas mixture and complex ambient air samples, we have successfully demonstrated that MI-SPI-MS will be a helpful tool to provide important complementary information on aromatics and alkanes in air, and proper application of MI-SPI-MS will benefit the real-time monitoring of trace VOCs in relative fields.

Enabling liquid vapor analysis using synchrotron VUV single photon ionization mass spectrometry with a microfluidic interface.

Vacuum ultraviolet (VUV) single photon ionization mass spectrometry (SPI-MS) is a vacuum-based technique typically used for the analysis of gas phase and solid samples, but not for liquids due to the challenge in introducing volatile liquids in a vacuum. Here we present the first demonstration of in situ liquid analysis by integrating the System for Analysis at the Liquid Vacuum Interface (SALVI) microfluidic reactor into VUV SPI-MS. Four representative volatile organic compound (VOC) solutions were used to illustrate the feasibility of liquid analysis. Our results show the accurate mass identification of the VOC molecules and the reliable determination of appearance energy that is consistent with ionization energy for gaseous species in the literature as reported. This work validates that the vacuum-compatible SALVI microfluidic interface can be utilized at the synchrotron beamline and enable the in situ study of gas-phase molecules evaporating off the surface of a liquid, which holds importance in the study of condensed matter chemistry.

All-solid-state deep ultraviolet laser for single-photon ionization mass spectrometry.

We report here the development of a reflectron time-of-flight mass spectrometer utilizing single-photon ionization based on an all-solid-state deep ultraviolet (DUV) laser system. The DUV laser was achieved from the second harmonic generation using a novel nonlinear optical crystal KBe2BO3F2 under the condition of high-purity N2 purging. The unique property of this laser system (177.3-nm wavelength, 15.5-ps pulse duration, and small pulse energy at ∼15 μJ) bears a transient low power density but a high single-photon energy up to 7 eV, allowing for ionization of chemicals, especially organic compounds free of fragmentation. Taking this advantage, we have designed both pulsed nanospray and thermal evaporation sources to form supersonic expansion molecular beams for DUV single-photon ionization mass spectrometry (DUV-SPI-MS). Several aromatic amine compounds have been tested revealing the fragmentation-free performance of the DUV-SPI-MS instrument, enabling applications to identify chemicals from an unknown mixture.

Online Analysis of Biomass Pyrolysis Tar by Photoionization Mass Spectrometry

The online analysis of volatiles from biomass pyrolysis (or gasification or combustion) is interesting because it has the ability to sample the volatiles directly from their reactive environment. The photon ionization (PI) is an efficient and soft ionization method for online analysis of biomass pyrolysis volatiles. Here, we review recent developments conducted in our groups on PI–mass spectrometry (MS) analysis of biomass pyrolysis volatiles by (1) synchrotron light PI–MS and (2) various commercial PI–MS techniques combined with various pyrolysis reactors. The fundamentals of PI–MS applied to biomass tar are briefly presented. The effect of photon energy on mass spectra from biomass volatiles is studied by synchrotron PI–MS. Different sources of PI–MS are then compared on vapors produced from fast pyrolysis in a microfluidized bed, namely, argon electron-beam-pumped excimer light (EBEL) vacuum ultraviolet (VUV) lamp single photon ionization (SPI)–MS (126 nm and 9.8 eV), laser Xe cell–SPI–MS (118 nm and 1...

Direct detection of the anti-cancer drug 9-phenylacridine in tissues by graphite rod laser desorption vacuum-ultraviolet post-ionization mass spectrometry.

Traditionally, drug analysis in biological tissue by mass spectrometry has required complicated sample pre-treatment, which not only wasted time, but also had adverse effects on the results. In order to assist assessment of potential drugs rapidly and accurately, a direct analytical method for drug detection in tissues is needed. The development of such a method is described in this study. An anti-cancer drug, 9-phenylacridine (ACPH), injected into the kidney of mice, was directly analysed from tissues placed on the surface of a graphite rod by near-infrared (1064 nm) laser desorption single photon ionization mass spectrometry (LD/SPI-MS). The LD/SPI-MS method was successfully validated by direct analysis of ACPH in kidney sections of mice, without any complicated and time-consuming sample pre-treatment. The sensitivity of detection was down to about 100 fmol per spot and the wide linear dynamic range allowed quantitative detection of ACPH in complex biological samples. A drug-time curve was acquired of ACPH in the kidney of mice after the drug had been injected into the caudal vein. It was demonstrated that the anti-tumor drug ACPH could be directly and rapidly detected by LD/SPI-MS in biological tissues without any time-consuming pre-treatment procedure. This method could potentially be applied to the selective localization and analysis of small molecule drugs in tissues and to the study of the pharmacokinetics of new drugs.

Realization of in-source collision-induced dissociation in single-photon ionization time-of-flight mass spectrometry and its application for differentiation of isobaric compounds.

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.

Evolved gas analysis by single photon ionization-mass spectrometry

The applicability of thermogravimetry (TG) coupled to single photon ionization time-of-flight mass spectrometry (TG-SPI-TOFMS) for evolved gas analysis (EGA) of coffee is demonstrated in this study. Coffee is a chemically well-known complex food product of large scientific and commercial interest. The roasting process of single green coffee beans (Arabica, Robusta) was simulated in the TG-SPI-TOFMS device, and the chemical composition of the evolved roasting gases was monitored on-line. Additionally, roasted and ground coffee powders of different types and brands as well as instant coffee were successfully investigated. For example, the diterpenes cafestol and kahweol can be detected among many other roasting products. These compounds can be of particular interest for quality control of coffee. It is shown that kahweol can be used as a tracer compound to discriminate arabica coffee species from robusta species.

Effusive molecular beam-sampled Knudsen flow reactor coupled to vacuum ultraviolet single photon ionization mass spectrometry using an external free radical source

A new apparatus using vacuum ultraviolet single photon ionization mass spectrometry (VUV SPIMS) of an effusive molecular beam emanating from a Knudsen flow reactor is described. It was designed to study free radical-molecule kinetics over a significant temperature range (300-630 K). Its salient features are: (1) external free radical source, (2) counterpropagating molecular beam and diffuse VUV photon beam meeting in a crossed-beam ion source of a quadrupole mass spectrometer with perpendicular ion extraction, (3) analog detection of the photocurrent of the free radical molecular cation, and (4) possibility of detecting both free radicals and closed shell species in the same apparatus and under identical reaction conditions owing to the presence of photoelectrons generated by the photoelectric effect of the used VUV-photons. The measured thermal molecular beam-to-background ratio was 6.35 ± 0.39 for Ar and 10.86 ± 1.59 for i-C4H10 at 300 K, a factor of 2.52 and 1.50 smaller, respectively, than predicted from basic gas-dynamic considerations. Operating parameters as well as the performance of key elements of the instrument are presented and discussed. Coupled to an external free radical source a steady-state specific exit flow of 1.6 × 10(11) and 5.0 × 10(11) molecule s(-1) cm(-3) of C2H5(●) (ethyl) and t-C4H9(●) (t-butyl) free radicals have been detected using VUV SPIMS at their molecular ion m/z 29 and 57, respectively, at 300 K.

On-line Analysis of Flavor Compounds in Toothpastes by Single Photon Ionization Mass Spectrometry

On-line Analysis of Flavor Compounds in Toothpastes by Single Photon Ionization Mass Spectrometry

Rapid on-site detection of explosives on surfaces by ambient pressure laser desorption and direct inlet single photon ionization or chemical ionization mass spectrometry

Considering current security issues, powerful tools for detection of security-relevant substances such as traces of explosives and drugs/drug precursors related to clandestine laboratories are required. Especially in the field of detection of explosives and improvised explosive devices, several relevant compounds exhibit a very low vapor pressure. Ambient pressure laser desorption is proposed to make these substances available in the gas phase for the detection by adapted mass spectrometers or in the future with ion-mobility spectrometry as well. In contrast to the state-of-the-art thermal desorption approach, by which the sample surface is probed for explosive traces by a wipe pad being transferred to a thermal desorber unit, by the ambient pressure laser desorption approach presented here, the sample is directly shockwave ablated from the surface. The laser-dispersed molecules are sampled by a heated sniffing capillary located in the vicinity of the ablation spot into the mass analyzer. This approach has the advantage that the target molecules are dispersed more gently than in a thermal desorber unit where the analyte molecules may be decomposed by the thermal intake. In the technical realization, the sampling capillary as well as the laser desorption optics are integrated in the tip of an endoscopic probe or a handheld sampling module. Laboratory as well as field test scenarios were performed, partially in cooperation with the Federal Criminal Police Office (Bundeskriminalamt, BKA, Wiesbaden, Germany), in order to demonstrate the applicability for various explosives, drugs, and drug precursors. In this work, we concentrate on the detection of explosives. A wide range of samples and matrices have been investigated successfully.