At Forensic Fluids Laboratories, we can identify and quantitate over 130 different compounds. For scientists looking for more information about oral fluid drug testing, Forensic Fluids provides the following summary of the detection process, advantages and associated instrumentation. Below, you'll also find references to various publications regarding tandem mass spectrometry, ELISA, LC/GC, and more.


ELISA Screening

Forensic Fluids Laboratories uses FDA approved ELISA (Enzyme Linked ImmunoSorbent Assay) plates for all of our drug screens. These plates are coated with polyclonal (rabbit) antibodies, making them less specific (that is, more likely to detect across a range of species) than monoclonal (mouse) antibodies.

This screening process tells you whether a sample is negative or positive for a certain drug or group of drugs (e.g., Opiates and Methamphetamines are groups of drugs, whereas PCP is a single drug) but does not give you a quantitative value or number. 

The immunoassay will also cross react with other chemicals/drugs that are structurally similar to each other. For example, Ephedrine and other cold pills cross-react with a Methamphetamine or Amphetamine screen, causing a false positive. False positives may also occur due to reactions with other medications as well.

For these reasons, all of our screens are followed by confirmation by LC/MS/MS (liquid chromatography tandem mass spectrometry), for positive identification and quantitation. 

LC/MS/MS Confirmation

Forensic Fluids Laboratories uses the most sensitive instruments available. The LC/MS/MS can detect lower levels than a single MS, and is also more accurate at identifying drugs. 

The scientific advantage of tandem mass spectrometry (MS/MS) is seen by the way it identifies peaks. Daughter, or fragment ions in Multiple Reaction Monitoring (MRM) analysis are inextricably sourced from one parent each. This makes this method more sensitive and accurate than single mass spectrometry. MRM, with tandem MS, provides exceptionally clean fragment ion chromatograms for quantification. By selectively detecting a product ion of interest from a specified precursor ion, the signal-to-noise ratio is optimized, thus lowering limits of detection (LOD). The MRM analysis mode sets MS1 to pass one parent at a time to the collision cell. This single parent ion is dissociated to fragment ions and these are measured by MS2.

The advantage of liquid chromatography (LC) is that it gives the laboratory the ability to analyze for many more drugs than gas chromatography (GC). Some compounds are not very amenable to GC, such as polar analytes, metabolites, and involatiles. Drugs do not need to be derivatized with liquid chromatography like they do with gas chromatography. Getting rid of this step decreases sample preparation time in some cases by more than one hour. Sample prep for liquid chromatography may be as easy as: pipet the saliva sample, add internal standard, centrifuge, and analyze.

Data collected for any daughters is exclusive to the parent from which it was sourced. Co-eluting parents may be monitored which produce the exact same fragment ions with no confounding of the data.

References

  • K.B. Scheidweiler, M.A. Huestis. A validated gas chromatographic-electron impact ionization mass spectrometric method for methylenedioxymethamphetamine (MDMA), methamphetamine and metabolites in oral fluid. Journal of Chromatography B. 835: 90-99 (2006)
  • K. Deventer, P. Van Eenoo, and F.T. Delbeke. Screening for amphetamine and amphetamine-type drugs in doping analysis by liquid chromatography/mass spectrometry. Rapid Communications in Mass Spectrometry. 20: 877-882 (2006)
  • T. Kuiper, Lacinda DeCicco, V. Spiehler, G. Sneed, and P. Kemp. Choice of an ELISA assay for screening postmortem blood for amphetamine and/or methamphetamine. Journal of Analytic Toxicology. 26: 513-518 (2002)
  • S.W.Toennes, S. Steinmeyer, H. Maurer, M.R. Moeller, and G.F. Kauert. Screening for drugs of abuse in oral fluid-correlation of analysis results with serum in forensic cases. Journal of Analytical Toxicology 29: 22-27 (2005)
  • S.W.Toennes, S. Steinmeyer, M.R. Moeller, and G.F. Kauert. Driving under the influence of drugs-evaluation of analytical data of drugs in oral fluid, serum and urine, and correlation with impairment symptoms. Forensic Science International 152: 149-255 (2005)
  • F.M. Wylie, H. Torrance, R.A. Anderson, and J.S. Oliver. Drugs in oral fluid Part I. Validation of an analytical procedure for licit and illicit drugs in oral fluid Forensic Science International. 150: 191-198 (2005)
  • R.J.F. Schepers, J.M. Oyler, R.E. Joseph, E.J. Cone, E.T. Moolchan, andM.A. Huestis. Methamphetamine and amphetamine pharmacokinetics in oral fluid and plasma after controlled oral methamphetamine administration to human volunteers. Clinical Chemistry 49: 121-132 (2003)
  • K.B. Scheidweiler, and M.A. Huestis. A validated gas chromatographic-electron impact ionization mass spectrometric method for methylenedioxymethamphetamine (MDMA), methamphetamine and metabolites in oral fluid. Journal of Chromotography B 835: 90-99 (2006)
  • M. Yonamine, N. Tawil, R.L. de Moraes Moreau, and O.A. Silva. Solid-phase micro-extraction-gas chromatography-mass spectrometry and headspace-gas chromatography of tetrahydrocannabinol, amphetamine, methamphetamine, cocaine and ethanol in saliva samples. Journal of Chromatography B 789: 73-78 (2003)
  • C. Chou, and M. Lee. Solid phase microextraction with liquid chromatography-electrospray ionization-tandem mass spectrometry for analysis of amphetamine and methamphetamine in serum. Analytica Chimica Acta 538: 49-56 (2005)
  • K.A. Mortier, K.E. Maudens, W.E. Lambert, K.M. Clauwaert, J.F. Van Bocxlaer, D.L. Deforce, C.H. Van Peteghem, A.P. De Leenheer. Simultaneous, quantitative determination of opiates, amphetamines, cocaine and benzoylecgonine in oral fluid by liquid chomatography quadrupole-time-of-flight mass spectometry. Journal of Chromatography B 779: 321-330 (2002).

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