ASTM E2677-14

5.1 ETDs are used by first responders, security screeners, the military, and law enforcement to detect and identify explosive threats quickly. ETDs typically operate by detecting chemical agents in residues and particles sampled from surfaces and can have detection limits for some compounds extending below 1 ng. An ETD is set to alarm when its response to any target analyte exceeds a programmed threshold level for that analyte. Factory settings of such levels typically balance sensitivity and selectivity assuming standard operating and deployment conditions.

5.2 A LOD is commonly accepted as the smallest amount of a particular substance that can be reliably detected in a given type of medium by a specific measurement process 5.3 When deployed, individual ETD performance (for example, realistic LODs) is influenced by: (5.4 Technical Challenges and Pitfalls to the Determination of LOD Values in ETDs and the Setting of Optimal Alarm Thresholds:

1.1 In harmony with the Joint Committee for Guides in Metrology (JCGM) and detection concepts of the International Union of Pure and Applied Chemistry (IUPAC) 1.2 Here, the limit of detection (LOD90) is defined to be the lowest mass of a particular compound deposited on a sampling swab for which there is 90 % confidence that a single measurement in a particular ETD will have a true detection probability of at least 90 % and a true nondetection probability of at least 90 % when measuring a process blank sample.

1.3 This particular test method was chosen on the basis of reliability, practicability, and comprehensiveness across tested ETDs, analytes, and deployment conditions. The calculations involved in this test method are published elsewhere 1.4 Intended Users—ETD developers, ETD vendors, ETD buyers, ETD testers, ETD users (first responders, security screeners, and the military), and agencies responsible for public safety and enabling effective deterrents to terrorism.

1.5 While this test method may be applied to any detection technology that produces numerical output, the procedures have been designed for ion mobility spectrometry (IMS) based ETD systems and tested with low vapor pressure explosive compounds. Compounds are deposited as liquid solutions on swabs and dried before use. As some swabs are absorbent, this deposition procedure may not be optimal for those ETD technologies that rely on high coverage of analyte on the surface of the swab. Background interferences introduced to the test samples were representative of a variety of conditions expected during deployment, but these conditions were not intended as comprehensive in representing all possible scenarios. The user should be aware of the possibility that untested scenarios may lead to failure in the determination of a reliable LOD90 value.

1.6 Units—The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Some specific hazards statements are given in Section 8 on Hazards.