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.

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.

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.