Forensic drug chemistry can be used in a variety of circumstances. One of the main purposes of testing is for use in court. Forensic chemists are often called upon to testify in court about their results and the procedures they used to analyze the samples.
Drugs can come in many shapes and forms. They can be “pills, powders, liquids,” mushrooms or leaves, “crystalline materials,” or be inserted into other materials like paper. Any number of items can be seized when investigators collect evidence, such as “the substance itself, containers used to transport the substance, utensils used to manufacture or use the substance, or in the case of manufacturing, the component chemicals used to create an illegal substance” (“A Simplified Guide”). Any evidence that is gathered is photographed and sealed up then sent to the lab for further testing.
The image above is crystal meth that had been seized by investigators.
Analysis is performed by trained drug chemists because of the importance that the results are accurate. Generally there are three steps to the testing process. The first is a weight test. This just determines the net weight of the sample and helps determine if there is enough of a substance present to be tested.
The second step is presumptive testing. This step, also called screening, “determines the general characteristics of the sample material and allows analysts to narrow down the field of confirmatory tests that will be used” (“A Simplified Guide”). Presumptive tests can include microscopic (examines structure of the sample), microcrystalline (crystals of the substance are grown and looked at under polarized light), ultraviolet spectroscopy (putting a UV light on a substance and observing how the material absorbs the light), and gas chromatography (primarily used to distinguish the different parts of a sample).
The third step is confirmatory testing. During this process, the sample is separated and the parts are compared with known materials. Several processes can be used to separate the compounds: gas chromatography (“dissolving the material in a liquid solvent, injecting the liquid into a superheated oven, vaporizing the liquid and pushing it through a very small, very long, glass capillary tube using a carrier gas such as helium or hydrogen. The mixture separates into individual chemical components inside the tube”), liquid chromatography (basically the same process as gas chromatography except the superheated oven step is removed. The material is dissolved and put straight into the tube), capillary electrophoresis (when the compound is inside the previously mentioned tube, an electrical field separates the parts), and wet chemistry (uses “liquid solvents to separate compounds”).
Some tools used in the identification processes are mass and infrared spectroscopy. Mass breaks apart the components of a substance using an electron beam. Infrared uses infrared light to determine the components in a sample. Different substances absorb light differently than others, and that information is compared to known reference materials to decide what a material is.
The process of identifying a material is a long and involved one, and it is very important that the technician performing the analysis is trained properly so the results of the analysis are accurate.
Source: “A Simplified Guide to Forensic Drug Chemistry.” Forensic Science Simplified. 2013. Web. 6 Feb. 2016.