Qualitative Analysis of Real Drug Evidence Using DART-MS and the Inverted Library Search Algorithm

Chromatographic-less mass spectrometry techniques like
direct analysis
in real-time mass spectrometry (DART-MS) are steadily being employed
as seized drug screening tools. However, these newer analytical platforms
require new computational methods to best make use of the collected
data. The inverted library search algorithm (ILSA) is a recently developed
method designed specifically for working with mass spectra of mixtures
collected with DART-MS and has been implemented as a function in the
NIST/NIJ DART-MS data interpretation tool (DIT). This paper demonstrates
how DART-MS and the ILSA/DIT can be used to analyze seized drug evidence,
while discussing insights gathered during the evaluation of 92 adjudicated
case samples. The evaluation verified that the combination of DART-MS
and the ILSA/DIT can be used as an informative tool to help analysts
screen seized drug evidence but also revealed several factorssuch
as the influence of incorporating multiple in-source fragmentation
spectra and the effect of scoring thresholdsan analyst must
consider while employing these methods. Use cases demonstrating the
benefit of the nonscoring metrics provided by the ILSA/DIT and demonstrating
how the ILSA/DIT can be used to identify novel substances are also
presented. A summary of considerations for using the ILSA/DIT for
drug screening concludes this paper.