Autonomous in situ analysis and real-time chemical detection using a backpack miniature mass spectrometer: concept, instrumentation development, and performance.

A major design objective of portable mass spectrometers is the ability to perform in situ chemical analysis on target samples in their native states in the undisturbed environment. The miniature instrument described here is fully contained in a wearable backpack (10 kg) with a geometry-independent low-temperature plasma (LTP) ion source integrated into a hand-held head unit (2 kg) to allow direct surface sampling and analysis. Detection of chemical warfare agent (CWA) simulants, illicit drugs, and explosives is demonstrated at nanogram levels directly from surfaces in near real time including those that have complex geometries, those that are heat-sensitive, and those bearing complex sample matrices. The instrument consumes an average of 65 W of power and can be operated autonomously under battery power for ca. 1.5 h, including the initial pump-down of the manifold. The maximum mass-to-charge ratio is 925 Th with mass resolution of 1-2 amu full width at half-maximun (fwhm) across the mass range. Multiple stages of tandem analysis can be performed to identify individual compounds in complex mixtures. Both positive and negative ion modes are available. A graphical user interface (GUI) is available for novice users to facilitate data acquisition and real-time spectral matching.

Arrays of low-temperature plasma probes for ambient ionization mass spectrometry.

RATIONALE: This paper reports the development of arrays of capillary-based low-temperature plasma (LTP) probes for direct sample analysis. These probe arrays allow a higher surface area to be analyzed, increasing the throughput in large sample analysis. Validation of these arrays was performed on illicit, cathinone-based drugs marketed as 'bath salts'. METHODS: LTP arrays consisting of 1, 7, and 19 probes were constructed with quartz capillaries and held together with silver epoxy resin adhesive. Three drugs, mephedrone, methylone and methylenedioxypyrovalerone, were analyzed with each plasma ion source and an ion trap mass spectrometer in full MS and in MS/MS positive ion mode. Chemical and thermal footprints were determined for each source. A reactive probe design was used to inject trifluoroacetic anhydride directly into the plasma stream for on-line derivatization. RESULTS: Small LTP probes and bundled arrays provide low picogram level limits of detection for mephedrone, methylone and methylenedioxypyrovalerone. Bundling the probes together in larger arrays increases the surface area analyzed by a factor of ten, while maintaining surface temperatures below 40 °C. Selectivity towards mephedrone and methylone was increased using trifluoracetylation under ambient ionization conditions. CONCLUSIONS: Low-temperature plasma ionization sources allow rapid detection of illicit 'bath salt' drugs in low amounts. The sources have a larger sampling area that allows faster detection of each analyte, and selectivity towards the selected drug is enhanced by adding reagents directly into the plasma stream.

Chemical analysis and chemical imaging of fragrances and volatile compounds by low-temperature plasma ionization mass spectrometry.

RATIONALE: The rapid analysis of volatile compounds, such as fragrances, is important in many commercial industries. The various ambient ionization methods have until now been largely applied to non-volatile or low-volatile compounds with success, and this study develops a semi-quantitative method for volatile compounds in commercial cleaning products. METHODS: Low-temperature plasma (LTP) ionization was used to perform rapid analysis, determine limits of detection (LODs) and perform chemical imaging on eight fragrances. Several mass analyzers including an ion trap, a quadrupole and an orbitrap were used to rapidly screen volatile compounds from cloth, paper, and glass and determine compositions present in a commercial cleaning product. Peltier cooling was used in some cases to enhance the retention time of compounds on a surface. RESULTS: This LTP method allowed the detection of fragrances in low picogram absolute amounts from glass, paper and cloth. Quantitation was demonstrated for compounds in a commercial cleaning product 1 min after the product was applied to a vinyl tile surface. High-throughput analysis and simultaneous detection of multiple compounds in a mixture were demonstrated with analysis times of less than 1 min. Modest spatial resolution (better than 1 cm) was achieved with LTP ionization. CONCLUSIONS: A semi-quantitative method has been demonstrated for the routine analysis of volatile and semi-volatile compounds. This method would be useful in quality control and production environments to determine product persistence, location of analytes and to complement olfactory studies for determining concentrations in the ambient environment.