BACKGROUND OF THE DISCLOSURE

The present invention generally relates to chemical detection systems and more specifically to illicit and dangerous substance trace detection systems, which are used in airports and other facilities for screening.

Ion Mobility Spectrometry (IMS) and Mass Spectrometry (MS) are known techniques for chemical detection.

Ion Mobility Spectrometry (IMS) is an atmospheric pressure chemical detection technology that is, in many ways, similar to Time-of-Flight Mass Spectrometry. Samples need to be in a gas phase for detection with an IMS system. Vaporized samples containing the analyte of interest are analyzed directly by drawing them into the IMS air flow system. Trace levels of explosive materials, drugs and chemical warfare agents can all be detected in this way. In existing IMS systems, samples are driven from a substrate or swab by applying heat from a desorber. Thus, non-volatile materials cannot be detected. Heat results in their decomposition rather than their desorption.

Sample material released into the IMS instrument by thermal desorption is then ionized to form reactant ion species from the gas employed in the system, normally air. Mixing these stable reactant ion clusters with vapor samples to be analyzed can result in ionization of the sampled materials, thus forming ion clusters characteristic of the sample material. A small packet of formed ions is guided by an electromagnetic field through a drift tube towards a detector, where they eventually strike a collector electrode to produce a signal. Ions travel through the drift tube guided by the electromagnetic field and opposed by a gas countercurrent. As a result, characteristic clusters of ions are formed based on analytes' size and shape, which in turn produce specific drift speeds that can be further correlated to a calibration standard to create a final plasmogram result.

FIG. 1illustrates, as prior art, an early portable IMS instrument generally indicated at10. A swab12, which has sampled an area of interest, is held in front of the inlet slot with a holder14. A desorber heater heats the air around the swab or the swab itself to release volatile trace chemicals from the sample swab. Once inside the instrument10, the gas analyte is ionized and passes through various magnetic grids to the collector/detector.

Mass Spectrometry (MS) is a similar analytical technique that ionizes chemical species and sorts the ions based on their mass-to-charge ratio. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures.

FIG. 2is a schematic of an exemplary magnetic sector mass spectrometer (MS) instrument generally indicated at20. In a typical MS testing procedure, a sample, which may be solid, liquid, or gas is first converted to vapor (operation not shown on schematic). The vapor22is ionized in an ionization region24, for example by a corona discharge needle. This may cause some of the molecules in the sample to break into charged fragments. These ions are then separated according to their mass-to-charge ratio, typically by accelerating them in an acceleration region26and then subjecting them to an electromagnetic field28. Ions of the same mass-to-charge ratio will undergo the same amount of deflection by the electromagnetic field28. The ions are counted by a detector30, such as an electron multiplier. Results are displayed as spectra of the relative abundance of detected ions as a function of the mass-to-charge ratio. The original structure of the analyte can be elucidated by the observed mass-to-charge ratio and characteristic fragmentation pattern.

For a number of different purposes, including environmental testing, law enforcement, security and field detection, samples requiring MS or IMS analysis are collected on swabs.

FIGS. 3a-3cillustrate a prior art rectangular swab50and holder52and introduction of the swab50into an exemplary prior art IMS instrument54for testing. At the present time, swabs collected for travel security screening are tested directly without further sample preparation primarily because of time and technique constraints. This is a balance between adequate security and the need to move people through checkpoints at a reasonable pace.

FIG. 4illustrates another prior art swab60and holder62.

FIG. 5still further illustrates additional swab shapes70,80,90currently being used in industry.

For obvious reasons, the reliability and speed of testing of the collected swabs is critical, for particularly for security screening at travel checkpoints, i.e. airports, cruise and border crossing. Accordingly, there is a perceived need for enhancement of the sample preparation to improve testing results without sacrificing testing speed.

SUMMARY OF THE INVENTION

The present disclosure teaches a novel sample preparation technique and provides an adapter/holder which aids in the delivery of the analyte into the instrument inlet and concurrently serves as an ionization source.

The technique includes adding a solvent to the swab to better dissolve and release any trace chemicals contained on the swab, charging of the solvated swab to create an ionized analyte prior to entry into the detection instrument, and positioning of the charged swab so that a sharp corner, or a shaped angled tip of the swab faces the inlet into the detection instrument. The technique may be referred to as Ambient Desorption Ionization (ADI).

In cases where the swab includes pre-existing corners, i.e. 90 degree square corners, or otherwise, the swab can be used without modification (see swabs50,70,80,90as illustrated inFIGS. 3aand5).

As a first step in the technique, the swab is positioned so that an optimally angled corner or tip (analyte release area) faces the instrument inlet port to aid in creation of a directed ionized plume at the inlet of the detector. The swab is preferably held in an adapter/holder which is integrated into, or is configured for mounting onto, or positioning in front of, an existing MS/IMS detector device so that the corner or angled tip is within ±5 mm of the entrance to detector. The adapter positions the swab and provides the high voltage connection. A solvent supply for the technique may also be supported by the adapter/holder.

The sample swab is energized by applying a high voltage to ionize the analyte and create ions which are directed toward the detector inlet. The detector inlet is grounded or has a differential potential in order to attract the ionized species into the detector inlet. The existing detector units thereafter function as intended for analysis.

In the alternative, if the swab lacks a pre-existing corner, such as the round swab60illustrated inFIG. 4, it can be quickly modified by cutting or otherwise shaping the swab. A shaping punch tool can be provided to quickly cut the swab60and create the desired angled tip or corner.

The novel technique is thus intended to improve release of chemical residue from the sample swabs and improve detection. Sample introduction and ionization are combined in a single step process making this invention particularly useful for MS/IMS, since this new technique allows non-volatile compounds to enter and flow through the instrument.

The invention advantageously allows the use of existing swabs directly as the ionization source, given the availability of a high voltage supply internal or external, and also eliminates the need for other types of ionization sources, for example radioactive material or corona discharge.

The ability to use present swab materials and holders is critically important in large scale deployment of the technique, and depending on the IMS or MS device, the present technique and adapter may require no change in swab materials; and if the instrument is presently portable, it remains so.

