Method and device for non-contact sampling and detection

Abstract

A system for the stand-off detection of trace amounts of analyte materials such as explosives, chemical warfare agents, toxic industrial chemicals, and the like includes an ion source that is operably connected to an ion collection means and to a sensor. The ion source employs a first gas that is passed through an electrical discharge to produce metastable gas molecules as well as charged particles of various kinds. Ions and other charged particles are removed from the first gas which is then reacted with a second gas having a lower ionization potential to obtain reactant ions of relatively uniform energy. The reactant ions are focused and accelerated into a beam that is directed upon a surface, such as luggage or clothing that is being interrogated, to produce analyte ions which are collected and passed into the sensor that is preferably a differential mobility spectrometer.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to a method and apparatus for the direct, non-contact, real-time sampling and detection of minute quantities of materials on surfaces. [0003] More particularly, this invention relates to a method and apparatus for producing ions from targeted sample molecules on or above a surface that is spaced apart from the apparatus and for detecting and identifying those ions, all without contacting the surface. [0004] 2. Description of Related Art [0005] Military and security needs, law enforcement concerns and environmental monitoring all require a capability to sample and detect minute quantities of explosives, drugs, chemical and biological agents, toxic industrial chemicals, and other targeted compounds of interest residing on or in a variety of materials and surfaces. Most users desire a fast, portable, simple, operator friendly detector that combines different detection capabilities in a single uni...

AI Technical Summary

Benefits of technology

[0027] The detector system of this invention includes two major parts. First is a reactant ion production device having the capability to produce reactant ions from introduced air or other gases, and to filter, focus and accelerate such reactant ions constrained within a sheath gas or not as appropriate, toward a surface, generating surface sample ions from the chemicals on that surface. Second is an ion collection device that collects surface sample ions produced by the interaction of reactant ions with sample chemicals on the surface. The ion collection device has the capability to transfer such sample ions from the ambient air in which they are collected to a controlled air stream, to introduce reactant gases or dopants that can modify the structure, charge and / or adduct formation or dissociation of the sample ions, and to introduce the ions into a differential mobility spectrometer. Events in the ion production and ion collection devices are fully coordinated to maximize sample ion production and collection. Feedback controls, using information from a rangefinder and the spectrometer or sensor, enable similar ion detection results to be obtained regardless of the distance between the detector and the surface.

Problems solved by technology

If vapor pressures of chemicals of interest are very low, they are undetectable by traditional screening methods or vapor must be produced from these materials.

These methods are time consuming, expensive and highly dependent upon trained operators capable of near perfect consistency in obtaining samples.

These factors limit screening to only a small portion of the samples that should be examined.

However, mass spectrometry requires large, heavy and expensive equipment making the technique impractical for applications that require portability.

There are several significant drawbacks to IMS including: Typical ion mobility spectrometer analysis cycles require 5-8 seconds from introduction of sample to alarm notification The percentage of ions produced that are actually detected is as low as 1% due to the ion gate, resulting in lower sensitivity Resolution among different ions is dependent upon the length of the drift region, making it difficult to miniaturize Reduction in the cross sectional area of the drift tube also decreases sensitivity, again making it difficult to miniaturize

Detection of such materials must be rapid, but also must be done with virtually no false negatives such that these materials go undetected when actually present, creating a potentially dangerous situation.

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