Research: Method Development and Validation for Drug Identification and Confirmation by LC/MS-MS for Limited-specimen Cases

Driving under the influence of drugs (DUID) cases represent the largest portion of cases handled in most forensic toxicology laboratories.  Blood is a commonly used specimen and is often analyzed using gas chromatography-mass spectrometry (GC/MS).  A common extraction for this method requires two milliliters of blood.  If more than one extraction is necessary, a larger volume of blood is required.  Recently, laboratories have started using liquid chromatography-mass spectrometry (LC/MS) to obtain a lower limit of detection and extractions which require less blood to complete.  Currently, the Oklahoma State Bureau of Investigation (OSBI) Laboratory operates LC-based extractions which require 250 to 500 microliters of sample to complete, but these are limited to specific drug classes.  A general drug screen for forty drugs has been developed and validated using 250 microliters of blood.  Even with this reduction of volume requirements, there are still instances in which less than one milliliter of blood is available for use by the analyst.  An additional validation has been completed which required 100 microliters of sample to confirm the presence of thirty-nine drugs.  A comparison between these methods was completed to verify the sensitivity of the 100 microliter method.

Danielle Ross-Carr – 2017