Liquid Chromatography Coupled to Isotope Ratio Mass Spectrometry Expanded to Include Organic Mobile Phases.

Current commercially available liquid chromatography coupled to isotope ratio mass spectrometry systems (LC-IRMS) oxidize all eluent and thus can only operate with all-aqueous mobile phases, limiting their application to a small subset of analytes and mixtures that can be separated without organic solvents. We report a novel rotating-catalytic disc desolvation device with subsequent laser-activated photocatalytic analyte combustion to create CO for high precision carbon isotope ratio measurements compatible with both aqueous and organic liquid mobile phases. Sucrose, glucose, androsterone, or androsterone acetate in 20% and 50% HO-CHOH solutions were introduced by flow injection to the interface to IRMS for sugars and steroids, respectively.

Fatty acid sentinels as covalently bound randomization standards for triacylglycerol (TAG) quantitative analysis.

Rationale: Quantitative analysis of triacylglycerols (TAG) is impeded by a lack of standards and the huge number of potential TAG molecular species that may be present due to the combinatorial nature of glycerolipids. Randomization of acyl groups yields TAG mixtures with profiles predictable from fatty acid profiles; however, their use as calibration mixtures has been limited.

Methods: We introduce here the principle of fatty acid isotopic sentinels that are quantitatively added prior to randomization to enable verification that randomization is complete, and that can be used as internal standards.

Structural Identification of Monounsaturated Branched Chain Fatty Acid Methyl Esters by Combination of Electron Ionization and Covalent Adduct Chemical Ionization Tandem Mass Spectrometry.

Monounsaturated fatty acids (-MUFA) and saturated branched chain fatty acids (BCFA) are structurally characterized by separate tandem mass spectrometry methods for double bond localization and for chain branching in their respective fatty acid methyl ester (FAME) derivatives; however, these methods have never been applied to branched monounsaturated FAME. Here, we report application of electron ionization (EI)-MS/MS and solvent-mediated covalent adduct chemical ionization (CACI)-MS/MS of monounsaturated BCFA methyl esters (MUBCFAME) of a chain length of 15-20 carbons. A novel system was used to implement CI with low vapor pressure reagents in a tabletop triple quadrupole MS.

Potentially High Value Conjugated Linolenic Acids (CLnA) in Melon Seed Waste.

Conjugated linolenic acids (CLnAs) are natural phytochemicals with known and potential bioactivities in mammals. Established CLnA sources are limited to a few common fruit seeds, notably pomegranate seeds and cherry pits, and the search for alternatives is impeded in part by cumbersome methods for reliable measurement. We investigated CLnA contents in lower value fruit seeds with a recently available facile mass spectrometry method, solvent-mediated chemical ionization, enabling and quantitative analysis.

Low Temperature Catalytic Combustion Reactors for High Precision Carbon Isotope Measurements in Gas Chromatography Combustion Isotope Ratio Mass Spectrometry.

Metal oxide-filled reactors constructed with ceramic tubes or fused silica capillary are widely used for combustion in gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS). However, they tend to be easily cracked or broken and prone to leaks at operating temperatures of ∼950 °C. Here we introduce a modified commercially available catalytic combustion/reduction methanizer to quantitatively convert organics to CO for δC analysis while retaining chromatographic resolution.

Cryofocus fast gas chromatography combustion isotope ratio mass spectrometry for rapid detection of synthetic steroid use in sport doping.

Sports doping requires high precision carbon isotope ratio (CIR) analysis of endogenous steroids using gas chromatography-combustion isotope ratio mass spectrometry (GCC-IRMS), however methods are relatively slow and cumbersome. A cryofocusing fast GCC-IRMS (Cryofocus Fast GCC-IRMS) was developed and optimized with minimal peak broadening using a programmable temperature vaporization (PTV) inlet and a low dead volume narrow-bore continuous capillary combustion interface to an IRMS. PTV injection, followed with cryofocusing before steroid analytes were volatilized by a hot jet, was used to initiate chromatography.

High-volume steroid isotopic standards developed as working standards for gas chromatography-combustion-isotope ratio mass spectrometry.

High-precision carbon isotope ratio analysis of urinary steroids by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) is the official test to detect illicit doping of synthetic versions of endogenous steroids, such as testosterone. Our group created the first steroid isotopic standards (SIS) specifically for World Anti-Doping Agency (WADA) accredited laboratories. The standards contain mixtures of steroids as acetates or free steroids at ~400 μg each per ampoule and have been widely distributed to anti-doping laboratories to facilitate comparability of inter-laboratory results.

Quantifying the contribution of grape hexoses to wine volatiles by high-precision [U¹³C]-glucose tracer studies.

Many fermentation volatiles important to wine aroma potentially arise from yeast metabolism of hexose sugars, but assessing the relative importance of these pathways is challenging due to high endogenous hexose substrate concentrations. To overcome this problem, gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) was used to measure high-precision (13)C/(12)C isotope ratios of volatiles in wines produced from juices spiked with tracer levels (0.01-1 APE) of uniformly labeled [U-(13)C]-glucose.

Toward unsupervised single-shot diffractive imaging of heterogeneous particles using X-ray free-electron lasers.

Single shot diffraction imaging experiments via X-ray free-electron lasers can generate as many as hundreds of thousands of diffraction patterns of scattering objects. Recovering the real space contrast of a scattering object from these patterns currently requires a reconstruction process with user guidance in a number of steps, introducing severe bottlenecks in data processing. We present a series of measures that replace user guidance with algorithms that reconstruct contrasts in an unsupervised fashion.

Highly sensitive and selective analysis of urinary steroids by comprehensive two-dimensional gas chromatography combined with positive chemical ionization quadrupole mass spectrometry.

Comprehensive two dimensional gas chromatography (GC × GC) provides greater separation space than conventional GC. Because of fast peak elution, a time of flight mass spectrometer (TOFMS) is the usual structure-specific detector of choice. The quantitative capabilities of a novel GC × GC fast quadrupole MS were investigated with electron ionization (EI), and CH(4) or NH(3) positive chemical ionization (PCI) for analysis of endogenous urinary steroids targeted in anti-doping tests.

Calibration and data processing in gas chromatography combustion isotope ratio mass spectrometry.

Compound-specific isotope analysis (CSIA) by gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) is a powerful technique for the sourcing of substances, such as determination of the geographic or chemical origin of drugs and food adulteration, and it is especially invaluable as a confirmatory tool for detection of the use of synthetic steroids in competitive sport. We review here principles and practices for data processing and calibration of GCC-IRMS data with consideration to anti-doping analyses, with a focus on carbon isotopic analysis ((13)C/(12)C). After a brief review of peak definition, the isotopologue signal reduction methods of summation, curve-fitting, and linear regression are described and reviewed.

Comprehensive 2-dimensional gas chromatography fast quadrupole mass spectrometry (GC × GC-qMS) for urinary steroid profiling: mass spectral characteristics with chemical ionization.

Comprehensive 2-dimensional gas chromatography (GC × GC), coupled to either a time of flight mass spectrometry (TOF-MS) or a fast scanning quadrupole MS (qMS) has greatly increased the peak capacity and separation space compared to conventional GC-MS. However, commercial GC × GC-TOFMS systems are not equipped with chemical ionization (CI) and do not provide dominant molecular ions or enable single ion monitoring for maximal sensitivity. A GC × GC-qMS in mass scanning mode was investigated with electron ionization (EI) and positive CI (PCI), using CH(4) and NH(3) as reagent gases.

Detection of synthetic testosterone use by novel comprehensive two-dimensional gas chromatography combustion-isotope ratio mass spectrometry.

We report the first demonstration of comprehensive two-dimensional gas chromatography combustion-isotope ratio mass spectrometry (GC×GCC-IRMS) for the analysis of urinary steroids to detect illicit synthetic testosterone use, of interest in sport doping. GC coupled to IRMS (GCC-IRMS) is currently used to measure the carbon isotope ratios (CIRs, δ(13)C) of urinary steroids in antidoping efforts; however, extensive cleanup of urine extracts is required prior to analysis to enable baseline separation of target steroids. With its greater separation capabilities, GC×GC has the potential to reduce sample preparation requirements and enable CIR analysis of minimally processed urine extracts.

Steroid isotopic standards for gas chromatography-combustion isotope ratio mass spectrometry (GCC-IRMS).

Carbon isotope ratio (CIR) analysis of urinary steroids using gas chromatography-combustion isotope ratio mass spectrometry (GCC-IRMS) is a recognized test to detect illicit doping with synthetic testosterone. There are currently no universally used steroid isotopic standards (SIS). We adapted a protocol to prepare isotopically uniform steroids for use as a calibrant in GCC-IRMS that can be analyzed under the same conditions as used for steroids extracted from urine.

Comprehensive two-dimensional gas chromatography combustion isotope ratio mass spectrometry.

We report the first coupling of comprehensive two-dimensional gas chromatography (GC x GC) to online combustion isotope ratio mass spectrometry (C-IRMS). A GC x GC system, equipped with a longitudinally modulated cryogenic system (LMCS), was interfaced to an optimized low dead volume combustion interface to preserve <300 ms full width at half-maximum (fwhm) fast GC peaks generated on the second GC column (GC2). The IRMS detector amplifiers were modified by configuration of resistors and capacitors to enable fast response, and a home-built system acquired data at 25 Hz.

Online aerosol mass spectrometry of single micrometer-sized particles containing poly(ethylene glycol).

The analysis of poly(ethylene glycol) (PEG)-containing particles by online single particle aerosol mass spectrometers equipped with laser desorption/ionization (LDI) is reported. We demonstrate that PEG-containing particles are useful in the development of aerosol mass spectrometers because of their ease of preparation, low cost, and inherently recognizable mass spectra. Solutions containing millimolar quantities of PEGs were nebulized and, after drying, the resultant micrometer-sized PEG-containing particles were sampled.

Following the biochemical and morphological changes of Bacillus atrophaeus cells during the sporulation process using Bioaerosol Mass Spectrometry.

Bioaerosol Mass Spectrometry (BAMS), a real-time single cell analytical technique, was used to follow the biochemical and morphological changes within a group of Bacillus atrophaeus cells by measuring individual cells during the process of sporulation. A mutant of B. atrophaeus that lacks the ability to produce dipicolinic acid (DPA) was also analyzed.

Desorption/ionization fluence thresholds and improved mass spectral consistency measured using a flattop laser profile in the bioaerosol mass spectrometry of single Bacillus endospores.

Bioaerosol mass spectrometry is being developed to analyze and identify biological aerosols in real time. Mass spectra of individual Bacillus endospores were measured with a bipolar aerosol time-of-flight mass spectrometer in which molecular desorption and ionization were produced using a single laser pulse from a Q-switched, frequency-quadrupled Nd:YAG laser that was modified to have an approximately flattop profile. The flattened laser profile allowed the minimum fluence required to desorb and ionize significant numbers of ions from single aerosol particles to be determined.

Bioaerosol mass spectrometry for rapid detection of individual airborne Mycobacterium tuberculosis H37Ra particles.

Single-particle laser desorption/ionization time-of-flight mass spectrometry, in the form of bioaerosol mass spectrometry (BAMS), was evaluated as a rapid detector for individual airborne, micron-sized, Mycobacterium tuberculosis H37Ra particles, comprised of a single cell or a small number of clumped cells. The BAMS mass spectral signatures for aerosolized M. tuberculosis H37Ra particles were found to be distinct from M.

Comprehensive assignment of mass spectral signatures from individual Bacillus atrophaeus spores in matrix-free laser desorption/ionization bioaerosol mass spectrometry.

We have fully characterized the mass spectral signatures of individual Bacillus atrophaeus spores obtained using matrix-free laser desorption/ionization bioaerosol mass spectrometry (BAMS). Mass spectra of spores grown in unlabeled, 13C-labeled, and 15N-labeled growth media were used to determine the number of carbon and nitrogen atoms associated with each mass peak observed in mass spectra from positive and negative ions. To determine the parent ion structure associated with fragment ion peaks, the fragmentation patterns of several chemical standards were independently determined.

Stable isotope labeling of entire Bacillus atrophaeus spores and vegetative cells using bioaerosol mass spectrometry.

Single vegetative cells and spores of Bacillus atrophaeus, formerly Bacillus subtilis var. niger, were analyzed using bioaerosol mass spectrometry. Key biomarkers were identified from organisms grown in 13C and 15N isotopically enriched media.

Reagentless detection and classification of individual bioaerosol particles in seconds.

The rapid chemical analysis of individual cells is an analytical capability that will profoundly impact many fields including bioaerosol detection for biodefense and cellular diagnostics for clinical medicine. This article describes a mass spectrometry-based analytical technique for the real-time and reagentless characterization of individual airborne cells without sample preparation. We characterize the mass spectral signature of individual Bacillus spores and demonstrate the ability to distinguish two Bacillus spore species, B.

Laser power dependence of mass spectral signatures from individual bacterial spores in bioaerosol mass spectrometry.

Bioaerosol mass spectrometry is being developed to analyze and identify biological aerosols in real time. Characteristic mass spectra from individual bacterial endospores of Bacillus subtilis var. niger were obtained in a bipolar aerosol time-of-flight mass spectrometer using a pulsed 266-nm laser for molecular desorption and ionization.