Rapid Screening and Quantification of PFAS Enabled by SPME-DART-MS.

Per- and polyfluoroalkyl substances (PFAS), an emerging class of toxic anthropogenic chemicals persistent in the environment, are currently regulated at the low part-per-trillion level worldwide in drinking water. Quantification and screening of these compounds currently rely primarily on liquid chromatography hyphenated to mass spectrometry (LC-MS). The growing need for quicker and more robust analysis in routine monitoring has been, in many ways, spearheaded by the advent of direct ambient mass spectrometry (AMS) technologies. Direct analysis in real time (DART), a plasma-based ambient ionization technique that permits rapid automated analysis, effectively ionizes a broad range of compounds, including PFAS. This work evaluates the performance of DART-MS for the screening and quantification of PFAS of different chemical classes, employing a central composite design (CCD) to better understand the interactions of DART parameters on their ionization. Furthermore, in-source fragmentation of the model PFAS was investigated based on the DART parameters evaluated. Preconcentration of PFAS from water samples was achieved by solid phase microextraction (SPME), and extracts were analyzed using the optimized DART-MS conditions, which allowed obtaining linear dynamic ranges (LDRs) within 10 and 5000 ng/L and LOQs of 10, 25, and 50 ng/L for all analytes. Instrumental analysis was achieved in less than 20 s per sample.

COVID-19, Personal Protective Equipment, and Human Performance.

Clinicians who care for patients infected with coronavirus disease 2019 (COVID-19) must wear a full suite of personal protective equipment, including an N95 mask or powered air purifying respirator, eye protection, a fluid-impermeable gown, and gloves. This combination of personal protective equipment may cause increased work of breathing, reduced field of vision, muffled speech, difficulty hearing, and heat stress. These effects are not caused by individual weakness; they are normal and expected reactions that any person will have when exposed to an unusual environment. The physiologic and psychologic challenges imposed by personal protective equipment may have multiple causes, but immediate countermeasures and long-term mitigation strategies can help to improve a clinician's ability to provide care. Ultimately, a systematic approach to the design and integration of personal protective equipment is needed to improve the safety of patients and clinicians.

Solvent-free, Noncontact Electrostatic Sampling for Rapid Analysis with Mass Spectrometry: Application to Drugs and Explosives.

A hand-held Van de Graaf generator is used to apply a high voltage, negligible current electrostatic potential to a wire mesh positioned in close proximity to a particle-laden surface in order to collect those particles for analysis. The electrostatic field effects transfer particles to the mesh without a requirement for mechanical contact between mesh and surface. Analysis of chemicals present in the sampled particles is completed by thermal desorption electrospray ionization. The utility of the method for noncontact sampling is demonstrated using solid drug powder samples, and inorganic explosives dispersed either on solid surfaces or in sand/soil in order to simulate common interfering matrices that might be encountered in the forensic environment. A metal mesh sampling substrate is utilized instead of traditional polymer-based swabs in order to permit thermal desorption at higher temperatures. The method leaves no visible trace of sampling leaving details such as a fingerprint image unperturbed, as demonstrated using fluorescence photography. Direct sampling of trace particles from hard surfaces and skin documents flexibility in the choice of sampling substrates, desorption temperatures, and sampling times. The potential of the device for use in forensic analyses is detailed.

Rapid fingerprinting of source and environmental microplastics using direct analysis in real time-high resolution mass spectrometry.

Microplastics are ubiquitous in the aquatic and terrestrial environment. To prevent further contamination, methods to determine their sources are needed. Techniques to quantify and characterize microplastics in the environment are still evolving for polymers and the additives and leachable substances embedded therein, which constitute the "chemical fingerprint" of an environmental microplastic. There is a critical need for analytical methods that yield such diagnostic information on environmental microplastics that enables identification of their composition and sources of pollution. This study reports on a novel approach for rapid fingerprinting of environmental microplastics and the screening of additives using Direct Analysis in Real Time (DART)-high resolution mass spectrometry. A variety of plastic samples were investigated, including virgin pre-production pellets, microbeads from personal care products, microplastics found in the aquatic environment, and synthetic fibers. The resulting mass spectra display ∼10,000 discrete peaks, corresponding to plastic additives released by thermal desorption and polymer degradation products generated by pyrolysis. These were used to characterize differences among plastic types, microplastic source materials, and environmental samples. Multivariate statistics and elemental composition analysis approaches were applied to analyze fingerprints from the mass spectra. This promising analytical approach is sensitive, (potentially) high-throughput, and can aid in the elucidation of possible sources of microplastics and perhaps eventually to the analysis of bulk environmental samples for plastics.

Effect of reducing sample volume on the detection of drugs in urine by transmission mode direct analysis in real time mass spectrometry.

RATIONALE: Matrix interference attributed to urea and other nitrogenous substances in unprocessed urine is significant. In this study desorption ionization of sub-microliter volume samples is performed in an effort to improve the detection of drugs in unprocessed urine using transmission mode-direct analysis in real time mass spectrometry (TM-DART-MS). METHODS: Urine samples were spiked with analytical standards of two drugs of abuse, codeine and methadone. Various sub-microliter volumes of unprocessed urine were deposited onto wire mesh screen consumables and analyzed using TM-DART for desorption ionization and a high-resolution mass spectrometer operated in full scan mode for mass analysis. A 22 factorial design of experiment (DOE) was employed to examine the effects of sample volume and sample introduction speed to the DART source. RESULTS: Results from analysis of one microliter and sub-microliter sample volumes were compared by measuring the signal produced by TM-DART-MS. Based on an α of 0.05, the lower-volume samples yielded spectra where the abundance of urea and creatinine ions was reduced, thus significantly improving the TM-DART-MS signal for drugs of abuse. Using slower sample introduction speeds increased the time during which the sample was exposed to the heated ionization gas, resulting in a significant increase in the TM-DART-MS signal. CONCLUSIONS: Reducing the sample volume to sub-microliter levels improved the detection of drugs of abuse present as either individual or multiple components of the untreated urine. The improved signal demonstrates the potential for using sub-microliter volumes for screening drugs in urine without the need for chromatography or sample pretreatment.

High-Throughput Extraction and Detection of Drugs in Urine: Parallel Sampling with Solid-Phase Microextraction (SPME) Fibers Coupled with Direct Analysis in Real Time-Mass Spectrometry (DART-MS) Detection.

Determination of drugs of abuse in urine is routinely accomplished by utilizing solid-phase extraction to isolate the drugs and gas chromatography/mass spectrometry (GC/MS) for their detection. Although robotic systems are employed, throughput is limited by the extraction process and GC chromatographic separation.A method that utilizes an array of 12 solid-phase microextraction (SPME) fibers for simultaneous isolation of drugs of abuse from urine is provided as a means to increase productivity. A SPME probe holder that permits movement of up to 12 fibers through the various steps of the extraction process in parallel is utilized. Use of an automated stage for fiber presentation into the ionization region of a Direct Analysis in Real Time equipped LC/MS facilitates rapid interrogation of each SPME.

Direct analysis in real time-Mass spectrometry (DART-MS) in forensic and security applications.

Over the last decade, direct analysis in real time (DART) has emerged as a viable method for fast, easy, and reliable "ambient ionization" for forensic analysis. The ability of DART to generate ions from chemicals that might be present at the scene of a criminal activity, whether they are in the gas, liquid, or solid phase, with limited sample preparation has made the technology a useful analytical tool in numerous forensic applications. This review paper summarizes many of those applications, ranging from the analysis of trace evidence to security applications, with a focus on providing the forensic scientist with a resource for developing their own applications. The most common uses for DART in forensics are in studying seized drugs, drugs of abuse and their metabolites, bulk and detonated explosives, toxic chemicals, chemical warfare agents, inks and dyes, and commercial plant and animal products that have been adulterated for economic gain. This review is meant to complement recent reviews that have described the fundamentals of the ionization mechanism and the general use of DART. We describe a wide range of forensic applications beyond the field of analyzing drugs of abuse, which dominates the literature, including common experimental and data analysis methods. © 2016 Wiley Periodicals, Inc. Mass Spec Rev 37:171-187, 2018.

A method for rapid sampling and characterization of smokeless powder using sorbent-coated wire mesh and direct analysis in real time - mass spectrometry (DART-MS).

Improvised explosive devices (IEDs) are often used by terrorists and criminals to create public panic and destruction, necessitating rapid investigative information. However, backlogs in many forensic laboratories resulting in part from time-consuming GC-MS and LC-MS techniques prevent prompt analytical information. Direct analysis in real time - mass spectrometry (DART-MS) is a promising analytical technique that can address this challenge in the forensic science community by permitting rapid trace analysis of energetic materials. Therefore, we have designed a qualitative analytical approach that utilizes novel sorbent-coated wire mesh and dynamic headspace concentration to permit the generation of information rich chemical attribute signatures (CAS) for trace energetic materials in smokeless powder with DART-MS. Sorbent-coated wire mesh improves the overall efficiency of capturing trace energetic materials in comparison to swabbing or vacuuming. Hodgdon Lil' Gun smokeless powder was used to optimize the dynamic headspace parameters. This method was compared to traditional GC-MS methods and validated using the NIST RM 8107 smokeless powder reference standard. Additives and energetic materials, notably nitroglycerin, were rapidly and efficiently captured by the Carbopack X wire mesh, followed by detection and identification using DART-MS. This approach has demonstrated the capability of generating comparable results with significantly reduced analysis time in comparison to GC-MS. All targeted components that can be detected by GC-MS were detected by DART-MS in less than a minute. Furthermore, DART-MS offers the advantage of detecting targeted analytes that are not amenable to GC-MS. The speed and efficiency associated with both the sample collection technique and DART-MS demonstrate an attractive and viable potential alternative to conventional techniques.

Detection of "bath salt" synthetic cathinones and metabolites in urine via DART-MS and solid phase microextraction.

A rapid and sensitive method, direct analysis in real time mass spectrometry (DART-MS) was applied to the characterization and semiquantitative analysis of synthetic cathinones and their metabolites in urine. DART-MS was capable of detecting three different cathinones and three metabolites down to sub-clinical levels directly without any sample preparations. The process produced a spectrum within seconds because no extraction or derivatization was required for analysis and the high mass accuracy of the instrumentation allowed analysis without the need for lengthy chromatographic separations. The use of solid phase microextration demonstrated a relative increase in the detectability of both drugs and metabolites, improving the detection signal on average more than an order of magnitude over direct detection, while providing cleaner spectra devoid of the major peaks associated with urine that oftentimes dominate such samples.

Evaluating a direct swabbing method for screening pesticides on fruit and vegetable surfaces using Direct Analysis in Real Time (DART) coupled to an Exactive benchtop orbitrap mass spectrometer.

Rapid screening of pesticides present on the surfaces of fruits and vegetables has been facilitated by using a Direct Analysis in Real Time (DART(®)) open air surface desorption ionization source coupled to an Exactive(®) high-resolution accurate mass benchtop orbitrap mass spectrometer. The use of cotton and polyester cleaning swabs to collect and retain pesticides for subsequent open air desorption ionization is demonstrated by sampling the surface of various produce to which solutions of pesticides have been applied at levels 10 and 100 times below the tolerance levels established by the United States Environmental Protection Agency (US EPA). Samples analyzed include cherry tomatoes, oranges, peaches and carrots each chosen for their surface characteristics which include: smooth, pitted, fuzzy, and rough respectively. Results from the direct analysis of fungicides on store-bought oranges are also described. In all cases, the swabs were introduced directly into the heated ionizing gas of the DART source resulting in production of protonated pesticide molecules within seconds of sampling. Operation of the orbitrap mass spectrometer at 25,000 full-width half maximum resolution was sufficient to generate high-quality accurate mass data. Stable external mass calibration eliminated the need for addition of standards typically required for mass calibration, thus allowing multiple analyses to be completed without instrument recalibration.

Increasing the rate of sample vaporization in an open air desorption ionization source by using a heated metal screen as a sample holder.

Rapid vaporization of sample into the ionizing gas exiting a direct analysis in real time (DART®) source has been enabled by directing a high electrical current through a metal wire screen to which sample has been applied. This direct heating of the screen enables rapid vaporization of sample as the wire temperature rises from room temperature to greater than 400°C in less than 20 s. Positioning the screen between the DART source and atmospheric pressure inlet of the mass spectrometer ensures that the ionizing gas is in close proximity to the sample molecules, resulting in efficient ionization while significantly reducing the time required for mass spectrometric analysis. The capability to modulate the electrical current flow through the wires facilitates either rapid desorption for the determination of single component samples or slower desorption where analysis of mixtures might be desired. The technology also enables deployment of strategies for the determination of chemicals present as powders that might otherwise require dissolution prior to analysis. Results from the use of this thermally assisted DART ('TA-DART') system for the analysis of pure compounds, simple mixtures, solids and low vapor pressure samples are presented.

Direct analysis in real time coupled with dried spot sampling for bioanalysis in a drug-discovery setting.

BACKGROUND: Conventional mouse or rat pharmacokinetic/toxicokinetic (PK/TK) studies frequently require sacrifice or use of multiple animals for a full time-course in order to obtain adequate blood volume. Currently accepted LC-MS/MS analyses require tedious sample preparation and large blood volume, therefore, a bioanalytical method with a simpler blood-sampling procedure using fewer animals, lower sample volume and no additional sample preparation is desirable. RESULTS: We have developed a method that combines the direct analysis in real time (DART) open-air ambient ionization source and MS/MS to directly analyze dried blood spots (DBS) on glass from low volume whole blood samples without additional sample preparation or manipulation of the spots. Single mouse serial bleeding was performed for sample collection for DART-MS/MS and the results were comparable to the conventional terminal bleeding method for LC-MS/MS. CONCLUSION: The DART-MS/MS method was applied to DBS sampling for PK/TK studies and also for in vitro screening of absorption, distribution, metabolism and excretion properties. The results from the DART-MS/MS approach correlated well with the LC-MS/MS analyses for comparison.

Principal component directed partial least squares analysis for combining nuclear magnetic resonance and mass spectrometry data in metabolomics: application to the detection of breast cancer.

Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) are the two most commonly used analytical tools in metabolomics, and their complementary nature makes the combination particularly attractive. A combined analytical approach can improve the potential for providing reliable methods to detect metabolic profile alterations in biofluids or tissues caused by disease, toxicity, etc. In this paper, (1)H NMR spectroscopy and direct analysis in real time (DART)-MS were used for the metabolomics analysis of serum samples from breast cancer patients and healthy controls. Principal component analysis (PCA) of the NMR data showed that the first principal component (PC1) scores could be used to separate cancer from normal samples. However, no such obvious clustering could be observed in the PCA score plot of DART-MS data, even though DART-MS can provide a rich and informative metabolic profile. Using a modified multivariate statistical approach, the DART-MS data were then reevaluated by orthogonal signal correction (OSC) pretreated partial least squares (PLS), in which the Y matrix in the regression was set to the PC1 score values from the NMR data analysis. This approach, and a similar one using the first latent variable from PLS-DA of the NMR data resulted in a significant improvement of the separation between the disease samples and normals, and a metabolic profile related to breast cancer could be extracted from DART-MS. The new approach allows the disease classification to be expressed on a continuum as opposed to a binary scale and thus better represents the disease and healthy classifications. An improved metabolic profile obtained by combining MS and NMR by this approach may be useful to achieve more accurate disease detection and gain more insight regarding disease mechanisms and biology.

Bioanalysis without sample cleanup or chromatography: the evaluation and initial implementation of direct analysis in real time ionization mass spectrometry for the quantification of drugs in biological matrixes.

Two key bottlenecks in pharmaceutical bioanalysis are sample cleanup and chromatographic separations. Although multiple approaches have been developed in the past decade to either shorten or multiplex these steps, they remain the rate limiting steps as ADME (Absorption, Distribution, Metabolism, and Excretion) property screening is being routinely incorporated into the drug discovery process. In this work, a novel system incorporating an automated Direct Analysis in Real Time (DART) ionization source coupled with a triple-quadrupole mass spectrometer has been developed and evaluated for quantitative bioanalysis. This system has the capability of directly analyzing samples from their biological matrixes and therefore potentially eliminating the need for sample cleanup and chromatographic separations. A LEAP Technologies autosampler was customized to perform the automated sample introduction into the DART beam with high precision, which significantly improved the reproducibility of the method. Additional pumping was applied to the atmospheric pressure inlet on the mass spectrometer to compensate for the increased vacuum load because of the use of high-flow helium by the DART. This resulted in an improvement of detection sensitivity by a factor of 10 to 100 times. Matrix effects for a diversified class of compounds were evaluated directly from untreated raw plasma and were found to range from approximately 0.05 to 0.7. Precision and accuracy were also tested for multiple test compounds over a dynamic range of four orders of magnitude. The system has been used to analyze biological samples from both in vivo pharmacokinetic studies and in vitro microsomal/S9 stability studies, and the results generated were similar to those obtained with conventional LC/MS/MS methods. Overall, this new automated DART-triple quadrupole mass spectrometer system has demonstrated significant potential for high-throughput bioanalysis.

Direct analysis in real time for reaction monitoring in drug discovery.

Direct analysis in real time (DART) is a novel ionization technique that provides for the rapid ionization of small molecules under ambient conditions. In this study, several commercially available drugs as well as actual compounds from drug discovery research were examined by LC/UV/ESI-MS and DART interfaced to a quadrupole mass spectrometer. For most compounds, the molecular ions observed by ESI-MS were observed by DART/MS. DART/MS was also studied as a means to quickly monitor synthetic organic reactions and to obtain nearly instantaneous molecular weight confirmations of final products in drug discovery. For simple, synthetic organic transformations, the trends in the intensities of the mass spectral signals for the reactant and product obtained by DART/MS scaled closely with those of the diode array or the total ion chromatogram obtained by LC/UV/ESI-MS. In summary, DART is a new tool that complements electrospray ionization for the rapid ionization and subsequent mass spectral analysis of compounds in drug discovery.

Atmospheric pressure laser desorption/ionization on porous silicon.

A recently developed commercial atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) source (MassTech, Inc.) was modified to adopt commercially available DIOS plates (Mass Consortium Corp.) for the studies of laser desorption from the surface of porous silicon under atmospheric pressure conditions. The feasibility of atmospheric pressure laser desorption/ionization from the surface of porous silicon (AP-DIOS) was demonstrated. The advantages of this new AP-DIOS technique include reasonably good sensitivity (subpicomole range for standard peptide mixtures), simplicity of sample preparation, uniformity of target spots and the absence of matrix peaks in the spectra. The AP-DIOS source was interfaced with a commercial ion trap (LCQ Classic, Thermo Finnigan) which additionally provides a unique MS(n) capability. The AP-DIOS spectrum of 250 fmol of unseparated tryptic digest of bovine serum albumin (BSA) was compared with that of AP-MALDI for the same compound. AP-DIOS offers significantly better coverage for the digest components in the mass range 200-1000 Da. The combined data of both techniques enabled us to nearly double the number of matched peaks in BSA digest analysis compared with AP-DIOS or AP-MALDI analysis separately.