Toxicology

The Toxicology Section of the Missouri State Highway Patrol Crime Lab is responsible for analyzing blood, urine, and other body fluids for alcohol, drugs, and poisons.The Toxicology Section performs analyses in a variety of cases including investigations of driving while intoxicated (DWI), investigations of fatal traffic crashes, investigations of unattended or unexplained deaths, drug violations, sexual assault cases, and homicides. The Toxicology Section is also responsible for analyzing alcoholic beverages in both criminal cases and administrative procedures.

Blood Alcohol Analysis

Approximately 35% of the cases received by the Toxicology Section involve a request for a blood alcohol analysis. Many of these cases are simply DWI investigations, but routinely the incident involves a serious traffic crash where people have been critically injured or killed. In most instances, a police officer investigating a DWI would request the suspect submit to breath alcohol analysis. However, if the suspect is unable due to injuries to complete a breath test, a blood sample must be collected and sent to the lab for analysis. Therefore, the DWI samples received by the Toxicology Section are usually from the most serious traffic crashes.

Alcohol analysis is a relatively simple procedure. While the primary focus of the analysis is the determination of the ethanol content of the blood, other related substances can also be found using the same analysis. The procedure is used to determine the concentration of ethanol, methanol, acetone, 2-propanol in blood and blood products, and qualitatively identify acetaldehyde and formaldehyde in blood and blood products. This procedure may also be used to qualitatively identify other volatile substances with similar chemical characteristics.

The procedure used by the Toxicology Section employs automated headspace gas chromatography with quantitation by internal standard integration. According to Henry's Law, at equilibrium, in a sealed vessel, volatile compounds in the liquid state will be present in the vapor state at a concentration proportional to the concentration in liquid. By sampling this vapor, i.e., the headspace, through a gas chromatograph, the volatile compound may be qualitatively identified and quantitatively measured. A single headspace injection is split into two capillary columns, each exiting to a flame ionization detector. One column is used for quantitation, the other for qualitative confirmation.

Criminalist loading chromatograph A Criminalist loading the headspace gas chromatograph

Gas Chromatograph The headspace gas chromatograph

Drug Testing

Approximately 65% of the cases received by the Toxicology Section involve a request for a drug test. A drug test on a blood or urine sample can be broken down into two parts: screening tests and confirmatory tests.

Drug Screening Tests

The Toxicology Section employs two drug screening methods which are immunoassay tests and thin layer/paper chromatography tests. The immunoassay tests are performed on the Abbott AxSYM System which uses the specific immunoassay technique known as fluorescence polarization immunoassay. The AxSYM is used to screen both blood and urine samples for the following classes or families of drugs:

  • amphetamine/methamphetamine - stimulants such as methamphetamine (crank, ice), amphetamine, and methylenedioxymethamphetamine (MDMA, Ecstasy)
  • barbiturates - sedatives such as butalbital (Fiorinal), phenobarbital, and pentobarbital (sodium pentothal)
  • benzodiazepines - tranquilizers such as diazepam (Valium) and alprazolam (Xanax)
  • cannabinoids - active chemicals in marihuana
  • cocaine metabolite - cocaine and its related metabolites
  • opiates - narcotic analgesics derived from opium such as codeine, morphine, heroin, oxycodone, and hydrocodone
  • phencyclidine - also know as PCP or angel dust
Lab Procedures

The other screening test employed in the Toxicology Section is a thin layer/paper chromatography method called Toxi-Lab A produced by Ansys Technologies. Using this method the criminalists in the Toxicology Section can analyze urine samples for a variety of drugs not included in the immunoassay screening test. Some of the drugs detectable using Toxi-Lab A are listed below:

  • Muscle relaxants: carisoprodol, meprobamate, methacarbamol
  • Narcotic analgesics: propoxyphene, meperidine, methadone, tramadol, pentazocine
  • Stimulants: methylphenidate, phentermine, methylenedioxymethamphetamine (MDMA), methylenedioxyamphetamine (MDA)
  • Sedatives: glutethimide, methaqualone, ketamine
  • Antidepressants: amitriptyline, nortriptyline, sertraline, fluoxetine, trimipramine, desipramine, imipramine, doxepin, trazodone, amoxapine
  • Anticonvulsants/antispasmodics: phenytoin, carbamazepine, trihexyphenidyl
  • Anti-inflammatories: naproxen, ketoprofen, ibuprofen
  • Local anesthetics: lidocaine, procaine
  • Antihistamines: chlorpheniramine, diphenhydramine, orphenadrine, doxylamine, hydroxyzine
  • Decongestants/broncodilators: ephedrine, pseudoephedrine, phenylpropanolamine, theophylline
  • Miscellaneous: strychnine, verapamil, acetaminophen, quinine, quinidine, psilocin, haloperidol, dextromethorphan

Confirmatory Tests

While screening tests are very accurate and reliable tests, they are not 100% accurate. Samples which screen positive are presumed to be actually positive, but the specific drug must be confirmed by a more specific method. The method employed by the Toxicology Section for all confirmations is gas chromatography/mass spectrometry (GC/MS).

In confirmatory tests, a procedure specific to the class or family of drug for which the sample screened positive is employed to "wash" or separate the drug itself from the matrix, i.e. blood or urine, in which it resides. The procedure of separating the drug from the sample is called an extraction. The Toxicology Section has different procedures for each class of drug. The general scheme of an extraction is to adjust the pH of the sample, expose the sample to an organic solvent to wash out the drug, collect and concentrate the organic solvent, and derivatize the drug in the sample. Some extractions have a but a few steps in the scheme, while others have many steps. The extraction process is one of the most time-consuming aspects of drug testing.

Once the drug has been extracted from the sample, it can then be analyzed and identified on the GC/MS instrument. The GC/MS instrument identifies drugs based on their discreet chemical structure. Identifying a chemical by its structure is the most accurate way to identify a chemical because the structure of a chemical is what makes a chemical unique and unlike any other chemical.

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