Screening and Extractions
Kenji Ota, CA DOJ
Screening Methods
With one exception, participants of these discussion groups are no longer using RIA. The
exception is one private lab using RIA for oxycodone screening. Overall, the reason for
dropping RIA was costs due to radioactive waste disposal.
EMIT when used is used primarily for urine samples, with again one exception where blood
samples are first precipitated and screened using this technique.
ELISA (EIA) was used by a majority of the participants. Opiates,
methamphetamine/amphetamine, benzodiazepines, cocaine, marijuana overall were the
drugs screened in common. PCP was included in many drug screen panels in the past but a
number of participants dropped this screen due to its relative rarity for the agencies served by
those labs. Barbiturates, methadone, propoxyphene, oxycodone, zolpidem, and carisoprodol
were other drugs/drug classes that were screened. Of note and of interest to some
participants was the finding that a fair number of driving cases were coming up positive for
carisoprodol.
By far, blood and urine were the most common matrices screened. Participants from
coroner’s laboratories screened other tissues, but made a comment that there were a lot of
false positives that required confirmatory testing, but immediate confirmations was the
standard operating procedure anyways. Other matrices were oral fluids, vitreous humor for
alcohol, spinal fluid, hair, and in one instance, maggots.
Almost all participants indicated that immediate confirmation of positive results after
screening was the standard operating procedure, which overall resulted in a significant
backlog.
Extraction Methods
Liquid/liquid extraction is still a predominant method for conducting extractions. All
participants used liquid/liquid extraction methods for a portion of their cases.
SPE is also used quite often, with polymeric columns (SPEware Cerex columns) very
enthusiastically promoted for ease of use, good flow characteristics, clean extracts, and good
recovery. Good results were also achieved by the various silica-based packed column
manufacturers. Participants indicated both blood and urine samples were extracted by SPE.
Benzodiazepines were mentioned as a problem class of drugs to analyze. 2 methods used
to successfully approach this problem was 1). acid/neural extraction followed by CI- analysis
and 2). extraction using SPEware Cerex Polycrom Clin II columns. The first method was a
DOJ Toxicology laboratory method; the second was mentioned by John Musselman of the
Phoenix Police Department Laboratory Services Bureau.
No extraction methods or GC/MS methods were forthcoming for the analysis of gabapentin;
there was a warning given by participants that what is observed is a GC breakdown product
when it is observed in cases.