Post-ICP Chemical Ionization MS for Total Extractable Organic Fluorine Quantitation.

Total extractable organic fluorine (EOF) quantitation complements targeted analyses to ensure complete accounting of all fluorochemicals in a sample. Notably, the prevalence of perfluoroalkyl substances has increased the need for total EOF quantitation due to the myriad forms of these chemicals and the limited availability of standards for targeted analysis. Here, we evaluate postplasma chemical ionization mass spectrometry (MS), an approach developed to address the limitations of inductively coupled plasma (ICP)-MS in F analysis, for total EOF quantitation.

Multielement Detection of Nonmetals by Barium-Based Post-ICP Chemical Ionization Coupled to Orbitrap-MS.

Prevalence of F, Cl, S, P, Br, and I in pharmaceuticals and environmental contaminants has promoted standard-free quantitation using analyte-independent heteroatom responses in inductively coupled plasma (ICP)-MS. However, in-plasma ionization challenges and element-dependent isobaric interference removal methods have hampered the multielement nonmetal detection in ICP-MS. Here, we examine an alternative approach to enhance multielement detection capabilities.

Solution Cathode Glow Discharge Coupled to Atmospheric Pressure Chemical Ionization for Elemental Detection of S and P in Organic Compounds.

We report a post-plasma chemical ionization approach to evaluate solution cathode glow discharge (SCGD) for S and P elemental analysis. Here, the SCGD serves as a reactor to produce chemical vapors for S and P from organic compounds containing these elements, while a corona discharge operated in negative mode is used to ionize the products. The approach creates long-lived ions in atmospheric pressure, enabling direct investigation of chemical vapor products via mass spectrometric and ion mobility separations.

Synthesis and Characterization of Cerium-Oxo Clusters Capped by Acetylacetonate.

Cerium-oxo clusters have applications in fields ranging from catalysis to electronics and also hold the potential to inform on aspects of actinide chemistry. Toward this end, a cerium-acetylacetonate (acac) monomeric molecule, Ce(acac) (), and two acac-decorated cerium-oxo clusters, [CeO(acac)(CHO)(CHOH)]·10.5MeOH () and [CeO(OH)(acac)(CHCOO)]·6(CHCN) (), were prepared and structurally characterized.

High-Resolution Elemental Mass Spectrometry Using LC-ICP-Nanospray-Orbitrap for Simultaneous and Species-Independent Quantitation of Fluorinated and Chlorinated Compounds.

Simultaneous elemental detection of F and Cl offers quantitation of fluorinated and chlorinated compounds and their transformation products without compound-specific standards. Despite wide-ranging applications, this capability has been hindered by fundamental and technical shortcomings of current inductively coupled plasma (ICP)-MS methods in ion formation and isobaric interference elimination. These hurdles are alleviated here via a chemical ionization method.

Effects of outdoor weathering and laundering on the detection and classification of fluorinated oil-and-water-repellent fabric coatings.

Fluorinated polymer coatings are used to impart durable oil-and-water-repellent properties on fabrics, potentially offering a persistent fiber characteristic for forensic fiber comparisons. To evaluate the persistence of these coatings, we investigate effects of outdoor weathering and laundering on detection and classification of the fluorinated oil-and-water-repellent coatings on 9 garments and 2 spray-coated fabric samples. Single fibers from the samples are pyrolyzed and subjected to gas chromatography coupled to a fluorine-selective detector.

Detection and diversity of fluorinated oil- and water-repellent coatings on apparel fibers.

Fluorinated coatings, often used for oil and water repellency and stain resistance in fabrics, are potentially persistent forensic fiber markers. However, they have received limited attention because of challenges in their detection caused by the small size of a single fiber and thin nature of stain-resistant coatings. Here, we utilize a sensitive fluorine-selective analytical technique to detect and evaluate diversity of fluorinated coatings in apparel.

Perturbation-induced high-frequency pulsing of nano-ESI with facile ion selection at atmospheric pressure.

Nano-ESI is a commonly used ionization technique with continually expanding analytical advantages. Here, we report a facile way for high-frequency (500-3800 Hz) pulsing of nano-ESI, providing a high flux of mobility-selected ions. The pulsing is accomplished using a relatively low-voltage modulation (80 V peak-to-peak) of an electrode placed <1 cm downstream of a nano-ESI emitter biased to a constant potential.

Elemental Fluorine Detection by Dielectric Barrier Discharge Coupled to Nanoelectrospray Ionization Mass Spectrometry for Nontargeted Analysis of Fluorinated Compounds.

The growing use of fluorochemicals has elevated the need for nontargeted detection of unknown fluorinated compounds and transformation products. Elemental mass spectrometry (MS) coupled to chromatography offers a facile approach for such analyses by using fluorine as an elemental tag. However, efficient ionization of fluorine has been an ongoing challenge.

Pulsed Nano-ESI: Application in Ion Mobility-MS and Insights into Spray Dynamics.

We have previously shown that pulsed nano-ESI offers direct ion introduction into an AP-IM cell in the absence of conventional gates and desolvation. Here, we further characterize this ion injection method and utilize it to gain insights into nano-ESI pulsed spray dynamics. We demonstrate that a pulsed nano-ESI operated at 20 Hz with ion generation pulses of 170-510 μs offers reproducible ion arrival times (0.

High-Sensitivity Elemental Mass Spectrometry of Fluorine by Ionization in Plasma Afterglow.

Fluorine elemental analysis using inductively coupled plasma mass spectrometry (ICPMS) is challenging because of low F ionization efficiency in the plasma and severe isobaric interferences. Notably, there is an increasing demand for ppb level fluorine measurements due to the rising importance of fluorinated compounds in pharmaceutical, environmental, and food analyses. Here, we report a new elemental ionization method where fluorinated analytes are introduced into an ICP to produce NaF followed by NaF formation in the atmospheric-pressure plasma afterglow.

Classifying single fibers based on fluorinated surface treatments.

Fibers are an important form of forensic evidence, but their evidential value can be severely limited when the identified characteristics of the fibers are common, such as blue cotton. Detecting chemical fiber treatments offers an avenue to further classify fibers and to improve their evidential value. In this report, we investigate the potential of fluoropolymer fiber coatings, used to impart oil and water-repellent properties in fabrics, for differentiating between fibers.

Atmospheric-Pressure Dielectric Barrier Discharge as an Elemental Ion Source for Gas Chromatographic Analysis of Organochlorines.

Atmospheric-pressure dielectric barrier discharge (AP-DBD) plasma has emerged in recent years as a versatile plasma for molecular ionization and elemental spectroscopy. However, its capabilities as an elemental ion source have been less explored, partly because of difficulties in the detection of positive elemental ions from this low-gas-temperature plasma. In this work, we investigate the detection of negative elemental ions to enable elemental mass spectrometry (MS) using AP-DBD.

Elemental quantitation of carbon via production of polyatomic anions in gas chromatography-plasma assisted reaction chemical ionization mass spectrometry.

Elemental mass spectrometry offers quantitation and isotopic analysis without the need for compound-specific standards. We have recently introduced plasma assisted reaction chemical ionization (PARCI) as an efficient elemental ionization method for halogens. Here, we report a new ionization chemistry in PARCI for facile quantitation of elemental carbon in gas chromatography eluates.

Pulsed Nano-ESI Atmospheric-Pressure Ion Mobility Mass Spectrometry with Enhanced Ion Sampling.

Ion mobility-mass spectrometry (IM-MS) has gained considerable attention for detection of clusters and weakly bound species created by electrospray ionization (ESI). Atmospheric-pressure (AP) IM-MS offers an advantage in these studies compared to its low-pressure counterpart, owing to soft introduction of ions into the mobility cell with minimal ion activation. Here, we report new approaches to improve the sensitivity and soft ion introduction in AP-IM-MS.

High-sensitivity elemental ionization for quantitative detection of halogenated compounds.

The rising importance of organohalogens in environmental, pharmaceutical, and biological applications has drawn attention to analysis of these compounds in recent years. Elemental mass spectrometry (MS) is particularly advantageous in this regard because of its ability to quantify without compound-specific standards. However, low sensitivity of conventional elemental MS for halogens has hampered applications of this powerful method in organohalogen analyses.

Gas chromatography plasma-assisted reaction chemical ionization mass spectrometry for quantitative detection of bromine in organic compounds.

We have recently introduced plasma-assisted reaction chemical ionization mass spectrometry (PARCI-MS) for elemental analysis of halogens in organic compounds. Here, we utilize gas chromatography (GC) coupled to PARCI-MS to investigate the mechanism of Br(-) ion generation from organobromines and to evaluate analytical performance of PARCI for organobromine analysis. Bromine atoms in compounds eluting from GC are converted to HBr in a low-pressure microwave induced helium plasma with trace amounts of hydrogen added as a reaction gas.

Plasma-assisted reaction chemical ionization for elemental mass spectrometry of organohalogens.

We present plasma-assisted reaction chemical ionization (PARCI) for elemental analysis of halogens in organic compounds. Organohalogens are broken down to simple halogen-containing molecules (e.g.

Reagent delivery by partial coalescence and noncoalescence of aqueous microdroplets in oil.

Reagent delivery constitutes a key step for reaction initiation in droplet-in-oil microfluidic platforms. Currently, this function is performed by complete fusion of a reagent droplet with the reactor droplet. The full coalescence, however, constrains the lower limit of volume delivery because reproducible droplet generation becomes exceedingly difficult as the reagent droplet volume is decreased.

Ambient analysis by thermal desorption atmospheric pressure photoionization.

Ambient mass spectrometry has attracted substantial attention in recent years. Among ambient ionization methods, thermal desorption ionization stands out because of two attributes: (1) simplicity, rendering the technique suitable for in-field applications, and (2) ability to couple with a variety of gas-phase ionization methods thereby broadening the range of molecules that can be analyzed with this method. Here, we report on improving the performance of a direct analysis in real time (DART) source by implementing atmospheric pressure photoionization (APPI) downstream of the desorption region.

Integrated microfluidic device for automated single cell analysis using electrophoretic separation and electrospray ionization mass spectrometry.

A microfabricated fluidic device was developed for the automated real-time analysis of individual cells using capillary electrophoresis (CE) and electrospray ionization-mass spectrometry (ESI-MS). The microfluidic structure incorporates a means for rapid lysis of single cells within a free solution electrophoresis channel, where cellular constituents were separated, and an integrated electrospray emitter for ionization of separated components. The eluent was characterized using mass spectrometry.

Single droplet separations and surface partition coefficient measurements using laser ablation mass spectrometry.

Surface activity of analytes plays a significant role in many chemical and physical phenomena. We present here a mass spectrometric method to characterize surface activity and solute partitioning between bulk liquid and the gas-liquid interface in droplets. The approach employs ablation by an infrared (IR) laser from the surface of a microliter droplet deposited on a stainless steel post.

Heat-assisted argon electrospray interface for low-flow rate liquid sample introduction in plasma spectrometry.

A heated (approximately 90 degrees C) laminar flow interface has been designed to assist in the development of an argon electrospray sample introduction system for low-flow rate applications using inductively coupled plasma (ICP) spectrometry. Previously, the stability and robustness of the ICP were compromised by the entrainment of air, N2, or gas mixtures (e.g.

Mass spectrometry of acoustically levitated droplets.

Containerless sample handling techniques such as acoustic levitation offer potential advantages for mass spectrometry, by eliminating surfaces where undesired adsorption/desorption processes can occur. In addition, they provide a unique opportunity to study fundamental aspects of the ionization process as well as phenomena occurring at the air-droplet interface. Realizing these advantages is contingent, however, upon being able to effectively interface levitated droplets with a mass spectrometer, a challenging task that is addressed in this report.

Charge assisted laser desorption/ionization mass spectrometry of droplets.

We propose and evaluate a new mechanism to account for analyte ion signal enhancement in ultraviolet-laser desorption mass spectrometry of droplets in the presence of corona ions. Our new insights are based on timing control of corona ion production, laser desorption, and peptide ion extraction achieved by a novel pulsed corona apparatus. We demonstrate that droplet charging rather than gas-phase ion-neutral reactions is the major contributor to analyte ion generation from an electrically isolated droplet.