Rapid Quantification of Ammonium Nitrate and Urea Nitrate Using Liquid Chromatography-High-Resolution Orbitrap Mass Spectrometry.

Resolution and sensitivity improvements in mass spectrometry technology have enabled renewed attempts at solving challenging analytical issues. One such issue involves the analysis of energetic ionic species. Energetic ionic species make up an important class of chemical materials, and a more robust and versatile analytical platform would provide tremendous value to the analytical community.

Implementation of normalized retention time (iRT) for bottom-up proteomic analysis of the aminoglycoside phosphotransferase enzyme facilitating method distribution.

Improvements in mass spectrometry technology to include instrument duty cycle, resolution, and sensitivity suggest mass spectrometry as a highly competitive alternative to conventional microbiological proteomic techniques. Targeted mass spectral analysis, sans prior empirical measurements, has begun to solely use the enormous amount of available genomic information for assay development. An in silico tryptic digestion of a suspected antibiotic-resistant enzyme using only its genomic information for assay development was achieved.

Rapid detection and quantification of aminoglycoside phosphorylation products using direct-infusion high-resolution and ultra-high-performance liquid chromatography/mass spectrometry.

Rationale: Worldwide efforts are underway to determine the extent of antimicrobial resistance (AMR). In 2015, the World Health Organization (WHO) founded the Global Antimicrobial Surveillance System (GLASS) focusing on surveillance and dissemination of data. In addition, the WHO advocates method development focused on rapid determination and close to real-time monitoring of antibiotic usage and its effectiveness.

Detection of acetyltransferase modification of kanamycin, an aminoglycoside antibiotic, in bacteria using ultrahigh-performance liquid chromatography tandem mass spectrometry.

Rationale: The occurrence of antibiotic-resistant bacteria is a worldwide issue that has the potential, if not addressed, to eliminate classes of antibiotics that have extended life expectancy in the last century. An approach to confront this threat is the development of technologies that greatly accelerate the detection of antibiotic resistance to minimize unnecessary treatment involving antibiotics. Development of an analytical method for rapid detection of aminoglycoside resistance using liquid chromatography/mass spectrometry (LC/MS) has not been reported in the literature and is described here.

Classification of Gunshot Residue Using Laser Electrospray Mass Spectrometry and Offline Multivariate Statistical Analysis.

Nonresonant laser vaporization combined with high-resolution electrospray time-of-flight mass spectrometry enables analysis of a casing after discharge of a firearm revealing organic signature molecules including methyl centralite (MC), diphenylamine (DPA), N-nitrosodiphenylamine (N-NO-DPA), 4-nitrodiphenylamine (4-NDPA), a DPA adduct, and multiple unidentified features not observed in previous mass spectral measurements. Collision-induced dissociation measurements of unknown GSR signature ions reveals inorganic barium and derivatives BaOH, BaOHCH, BaCHCOO remaining from the primer. Both hydrophilic and hydrophobic signatures are detected using water-methanol electrospray solution.

Increasing protein charge state when using laser electrospray mass spectrometry.

Femtosecond (fs) laser vaporization is used to transfer cytochrome c, myoglobin, lysozyme, and ubiquitin from the condensed phase into an electrospray (ES) plume consisting of a mixture of a supercharging reagent, m-nitrobenzyl alcohol (m-NBA), and trifluoroacetic acid (TFA), acetic acid (AA), or formic acid (FA). Interaction of acid-sensitive proteins like cytochrome c and myoglobin with the highly charged ES droplets resulted in a shift to higher charge states in comparison with acid-stable proteins like lysozyme and ubiquitin. Laser electrospray mass spectrometry (LEMS) measurements showed an increase in both the average charge states (Zavg) and the charge state with maximum intensity (Zmode) for acid-sensitive proteins compared with conventional electrospray ionization mass spectrometry (ESI-MS) under equivalent solvent conditions.

Determination of internal energy distributions of laser electrospray mass spectrometry using thermometer ions and other biomolecules.

The internal energy distributions for dried and liquid samples that were vaporized with femtosecond duration laser pulses centered at 800 nm and postionized by electrospray ionization-mass spectrometry (LEMS) were measured and compared with conventional electrospray ionization mass spectrometry (ESI-MS). The internal energies of the mass spectral techniques were determined by plotting the ratio of the intact parent molecular features to all integrated ion intensities of the fragments as a function of collisional energy using benzylpyridinium salts and peptides. Measurements of dried p-substituted benzylpyridinium salts using LEMS resulted in a greater extent of fragmentation in addition to the benzyl cation.

Laser electrospray mass spectrometry minimizes ion suppression facilitating quantitative mass spectral response for multicomponent mixtures of proteins.

A comparison of the mass spectral response for myoglobin, cytochrome c, and lysozyme is presented for laser electrospray mass spectrometry (LEMS) and electrospray ionization-mass spectrometry (ESI-MS). Analysis of multicomponent protein solutions using nonresonant femtosecond (fs) laser vaporization with electrospray postionization mass spectrometry exhibited significantly reduced ion suppression effects in comparison with conventional ESI analysis, enabling quantitative measurements over 4 orders of magnitude in concentration. No significant charge reduction was observed in the LEMS experiment while the ESI measurement revealed charge reduction for myoglobin and cytochrome c as a function of increasing protein concentration.

Quantitative measurements of small molecule mixtures using laser electrospray mass spectrometry.

Quantitative measurements of atenolol, tioconazole, tetraethylammonium bromide, and tetrabutylammonium iodide using laser electrospray mass spectrometry (LEMS) reveal monotonic signal response as a function of concentration for single analytes, two- and four-component equimolar mixtures, and two-component variable molarity mixtures. LEMS analyses of single analytes as a function of concentration were linear over ~2.5 orders of magnitude for all four analytes and displayed no sign of saturation.

Classification of smokeless powders using laser electrospray mass spectrometry and offline multivariate statistical analysis.

A direct, sensitive, and rapid method for the detection of smokeless powder components, from five different types of ammunition, is demonstrated using laser electrospray mass spectrometry (LEMS). Common components found in powder, such as ethyl centralite, methyl centralite, dibutyl phthalate, and dimethyl phthalate, are detected under atmospheric conditions without additional sample preparation. LEMS analysis of the powders revealed several new mass spectral features that have not been identified previously.