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.

Reconfigurable acquisition system with integrated optics for a portable flow cytometer.

Portable and inexpensive scientific instruments that are capable of performing point of care diagnostics are needed for applications such as disease detection and diagnosis in resource-poor settings, for water quality and food supply monitoring, and for biosurveillance activities in autonomous vehicles. In this paper, we describe the development of a compact flow cytometer built from three separate, customizable, and interchangeable modules. The instrument as configured in this work is being developed specifically for the detection of selected Centers for Disease Control (CDC) category B biothreat agents through a bead-based assay: E. coli O157:H7, Salmonella, Listeria, and Shigella. It has two-color excitation, three-color fluorescence and light scattering detection, embedded electronics, and capillary based flow. However, these attributes can be easily modified for other applications such as cluster of differentiation 4 (CD4) counting. Proof of concept is demonstrated through a 6-plex bead assay with the results compared to a commercially available benchtop-sized instrument.

Study of Discontinuous Atmospheric Pressure Interfaces for Mass Spectrometry Instrumentation Development.

The discontinuous atmospheric pressure interface (DAPI) has allowed the transfer of ions from atmospheric pressure ionization sources to an ion trap mass analyzer in hand-held mass spectrometers with miniature pumping systems at transfer efficiencies high enough for proper chemical analysis. The DAPI potentially would allow a significant enhancement to the mass analysis efficiency of laboratory-scale mass spectrometers, which have pumping systems of much larger capacities. A laboratory-scale mass spectrometer with a DAPI-RIT (rectilinear ion trap)-DAPI configuration has been developed to explore this possibility. The gas dynamic effects on ion trapping and mass analysis have been studied at various conditions. A pulsed nanoelectrospray ionization source synchronized with the DAPI has been implemented to improve the sample usage efficiency as well as to adjust the number of ions to be trapped for MS analysis, so that space charge effects can be avoided. Single-scan spectra of peptides were recorded with an ionization time as short as 1 mus, corresponding to an analyte consumption of several attomoles. The simplicity of application of the DAPI for performing ion/molecule and ion/ion reactions has also been demonstrated with proton transfer and electron transfer dissociation reactions with peptides.

Study of discontinuous atmospheric pressure interfaces for mass spectrometry instrumentation development.

The discontinuous atmospheric pressure interface (DAPI) has allowed the transfer of ions from atmospheric pressure ionization sources to an ion trap mass analyzer in hand-held mass spectrometers with miniature pumping systems at transfer efficiencies high enough for proper chemical analysis. The DAPI potentially would allow a significant enhancement to the mass analysis efficiency of laboratory-scale mass spectrometers, which have pumping systems of much larger capacities. A laboratory-scale mass spectrometer with a DAPI-RIT (rectilinear ion trap)-DAPI configuration has been developed to explore this possibility. The gas dynamic effects on ion trapping and mass analysis have been studied at various conditions. A pulsed nanoelectrospray ionization source synchronized with the DAPI has been implemented to improve the sample usage efficiency as well as to adjust the number of ions to be trapped for MS analysis, so that space charge effects can be avoided. Single-scan spectra of peptides were recorded with an ionization time as short as 1 micros, corresponding to an analyte consumption of several attomoles. The simplicity of application of the DAPI for performing ion/molecule and ion/ion reactions has also been demonstrated with proton transfer and electron transfer dissociation reactions with peptides.