Ambient Sampling/Ionization Mass Spectrometry: Applications and Current Trends

Direct, trace level detection of explosives on ambient surfaces by desorption electrospray ionization mass spectrometry

1. Scope of this Review 2270 2. Ambient Ionization Techniques 2272 2.1. Solid−Liquid Extraction-Based Techniques 2272 2.1.1. Desorption Electrospray Ionization (DESI) 2272 2.1.2. Desorption Ionization by Charge Exchange (DICE) 2277 2.1.3. Easy Ambient Sonic-Spray Ionization (EASI) 2278 2.1.4. Liquid Micro Junction Surface Sampling Probe (LMJ-SSP) 2279 2.1.5. Liquid Extraction Surface Analysis (LESA) 2279 2.1.6. Nanospray Desorption Electrospray Ionization (nanoDESI) 2280 2.1.7. Desorption Atmospheric Pressure Photoionization (DAPPI) 2280 2.2. Plasma-Based Techniques 2281 2.2.1. Direct Analysis in Real Time (DART) 2282 2.2.2. Flowing Atmospheric-Pressure Afterglow (FAPA) 2286 2.2.3. Low Temperature Plasma (LTP) & Dielectric Barrier Discharge Ionization (DBDI) 2286 2.2.4. Chemical Sputtering/Ionization Techniques 2287 2.3. Two-Step Thermal/Mechanical Desorption/ Ablation (Non-Laser) Techniques 2288 2.3.1. Neutral Desorption Extractive Electrospray Ionization (ND-EESI) 2288 2.3.2. Beta Electron-Assisted Direct Chemical Ionization (BADCI) 2288 2.3.3. Atmospheric Pressure Thermal Desorption-Secondary Ionization (AP-TD/SI) 2289 2.3.4. Probe Electrospray Ionization (PESI) 2289 2.4. Two-Step Laser-Based Desorption Ablation Techniques 2290 2.4.1. Laser-Based Hybrid Techniques Coupled to ESI or Plasma Ionization 2290 2.4.2. Laser Electrospray Mass Spectrometry (LEMS) 2292 2.4.3. Laser Ablation Atmospheric Pressure Photoionization (LAAPPI) 2293 2.4.4. Laser Ablation Sample Transfer 2293 2.5. Acoustic Desorption Techniques 2294 2.5.1. Laser-Induced Acoustic Desorption (LIAD) 2294 2.5.2. Radiofrequency Acoustic Desorption Ionization (RADIO) 2295 2.5.3. Surface Acoustic Wave-Based Techniques 2295 2.6. Multimode Techniques 2296 2.6.1. Desorption Electrospray/Metastable-Induced Ionization (DEMI) 2296 2.7. Other Techniques 2296 2.7.1. Rapid Evaporative Ionization Mass Spectrometry (REIMS) 2296 2.7.2. Laser Desorption Ionization (LDI) 2297 2.7.3. Switched Ferroelectric Plasma Ionizer (SwiFerr) 2297 2.7.4. Laserspray Ionization (LSI) 2297 3. Remote Sampling 2298 3.1. Nonproximate Ambient MS 2298 3.2. Fundamentals of Neutral/Ion Transport 2298 3.3. Transport of Neutrals 2298 3.4. Transport of Ions 2299 4. Future Directions 2300 Author Information 2300 Corresponding Author 2300 Author Contributions 2300 Notes 2300 Biographies 2300 Acknowledgments 2301 References 2301

Mass Spectrometry: Recent Advances in Direct Open Air Surface Sampling/Ionization

The energy balance at substrate surfaces during plasma processing

Understanding the interaction of N2 with iron is relevant to the iron catalyst used in the Haber process and to possible roles of the FeMoco active site of nitrogenase. The work reported here uses synthetic compounds to evaluate the extent of NN weakening in low-coordinate iron complexes with an FeNNFe core. The steric effects, oxidation level, presence of alkali metals, and coordination number of the iron atoms are varied, to gain insight into the factors that weaken the NN bond. Diiron complexes with a bridging N2 ligand, LRFeNNFeLR (LR = β-diketiminate; R = Me, tBu), result from reduction of [LRFeCl]n under a dinitrogen atmosphere, and an iron(I) precursor of an N2 complex can be observed. X-ray crystallographic and resonance Raman data for LRFeNNFeLR show a reduction in the N−N bond order, and calculations (density functional and multireference) indicate that the bond weakening arises from cooperative back-bonding into the N2 π* orbitals. Increasing the coordination number of iron from three to four t...

/pdf/studies-of-low-coordinate-iron-dinitrogen-complexes-3algagxr1i.pdf

Studies of low-coordinate iron dinitrogen complexes.

A method of preparing modified surfaces, referred to as soft-landing, is described in which intact polyatomic ions are deposited from the gas phase into a monolayer fluorocarbon surface at room temperature. The ions are trapped in the fluorocarbon matrix for many hours. They are released, intact, upon sputtering at low or high energy or by thermal desorption, and their molecular compositions are confirmed by isotopic labeling and high-resolution mass measurements. The method is demonstrated for various silyl and pyridinium cations. Capture at the surface is favored when the ions bear bulky substituents that facilitate steric trapping in the matrix.

https://science.sciencemag.org/content/sci/275/5305/1447.full.pdf

Soft-Landing of Polyatomic Ions at Fluorinated Self-Assembled Monolayer Surfaces

Soft landing of polyatomic ions for selective modification of fluorinated self-assembled monolayer surfaces

https://link.springer.com/content/pdf/10.1016/1044-0305(93)80033-U.pdf

Surface-induced dissociation from a liquid surface

Ferrocene molecular ions undergo inelastic collisions at Si(100) and alkanethiol self-assembled monolayer surfaces (SAMs). Dissociation of the activated projectile follows its recoil from the surface; viz., surface-induced dissociation (SID) occurs by a two-step mechanism, and the fragmentation pattern is independent of the nature of the surface. On the other hand, the SID efficiency for collisions at the SAM surfaces is much greater than that for the Si(100) single-crystal surface as a result of a decrease in neutralization at the organic surfaces. The fragmentation pathways of a ferrocene molecular ion are elucidated as a function of collision energy and presented as energy-resolved mass spectra (ERMS) on the SAM and Si(100) surfaces

Energy disposal and target effects in hyperthermal collisions of ferrocene molecular ions at surfaces

Collisions of C3F at self-assembled hydrocarbon, deuterated hydrocarbon and fluorocarbon surfaces yield fragment ions which are characteristics of both electronic excitation and vibrational excitation. Direct electronic excitation is indicated by loss of F˙, which has been shown previously to be diagnostic of this type of excitation process. Electronic excitation is favored by low-energy collisions at the hydrocarbon surface. Even the change to the corresponding deuterated surface produces a large effect in favor of the normal vibrational excitation process. This change in mechanism with the nature of the target shows up as a dramatic isotope effect in the surface-induced dissociation (SID) mass spectra. The control over the excitation process exhibited by the effective mass of the target is probably exerted through its effect on the relative velocity of the collision partners. The fluorinated surfce is more effective than the others in conversion of translational into internal energy and in minimizing ion loss through neutralization and other processes which compete with SID. The fluorinated surfaces yield spectra that are largely free from chemical sputtering, a process which occurs even at ultra-high vacuum for stainless-steel surfaces which are not rigorously cleaned. The internal energy deposition associated with chemical sputtering increases with increaisng collision energy. Several of the fluorocarbon fragment ions generated from perfluoropropylene have also been examined at self-assembled monolayer surfaces and they are well behaved in their SID and chemical sputtering reactions. This in contrast to the low efficiency of SID and high sputtering efficiency observed in previous studies at uncharacterized multi-layer hydrocarbon-covered surfaces.

S. A. Miller

Papers

Soft-Landing of Polyatomic Ions at Fluorinated Self-Assembled Monolayer Surfaces

Soft landing of polyatomic ions for selective modification of fluorinated self-assembled monolayer surfaces

Surface-induced dissociation from a liquid surface

Energy disposal and target effects in hyperthermal collisions of ferrocene molecular ions at surfaces

Collisions of fluorocarbon ions at solid surfaces: electronic excitation, surface-induced dissociation and chemical sputtering