SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists

A70
FAST SCREENING AND IDENTIFICATION OF DRUGS USING RETENTION TIME
LOCKINGIRESUL TS SCREENER BY GC-MS
Rosa E. De Jesus·, Robert A. Middleberg; National Medical Services, Willow Grove, PA 19090
A major challenge for all forensic toxicology laboratories is to isolate, detect, identify and quantify the
wide array of toxicants or drugs that may be present in a case where the cause of death is unknown. It is a
challenge to screen, in a single analysis, hundreds of the most common toxicants that could be present.
However, the use of a retention time locking process with GCIMS analysis affords this opportunity. This
very powerful tool allows for the automated, rapid screening and identification of mUltiple analytes in just
one injection. This tool combines the two key characteristics for the positive identification of a compound:
retention time and mass spectra. After maintenance of the chromatographic system (Le. cutting or
changing the column), the retention times of the analytes can drift, which makes the positive identification
of analytes more time-consuming. Furthermore, although two or more instruments may be running under
the same conditions, the retention times of those analytes may not be the same. However, when using
retention time locking, the inlet pressure is adjusted and the methods are locked to that pressure, resulting
in consistent retention times of all compounds from run to run. With the use of this technique the event
times of the method will stay the same, allowing the comparison of real time data with previously acquired
data. Also the chromatograms can be superimposed, leading to easy observation and comparison of
patterns. Retention time locking is used then in conjunction with a results screener, where a database is
created for the locked methods. Results screener contains information of the target and qualifier ions ofthe
analytes of interest, with their relative intensities, at their expected retention times. Therefore, every
injection is made using a locked method containing a previously created database, and the system scans for
the ions produced associated with an analyte in a window at its expected retention time. This allows for
rapid identification of all compounds, including coeluting analytes. This detection and identification of the
compounds in the sample, based on retention time and mass spectra, is achieved automatically in justa few
seconds. The information obtained is then reviewed by the analyst and summarized in a customized report.
Having no limits in the number of compounds that can be included in the database, retention time locking /
results screener is a very powerful automated tool for the fast screening and identification of compounds in
a sample. The use of this tool will be demonstrated as it is utilized for the routine analysis of toxicology
samples.
Keywords: Retention time locking; GC-MS drug screening; Drug identification
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