Washington’s Crime Laboratory Division (CLD) is responsible for testing solids and liquids of varying amounts and sizes for drug identification. It uses two separate techniques1 to identify the chemical composition of unknown substances: (1) Fourier Transform Infrared Spectrometer (FTIR) and (2) Gas Chromatography Mass Spectrometry (GCMS). Both techniques must be used to identify drugs, and both require significant training and experience for method development2 and interpretation.
FTIR irradiates the atoms of organic molecules with infrared energy to detect covalent bonds, i.e., a molecular structure that is based on the bonding of electron groups. In simple terms, FTIR is looking for covalent bonds (parts of the atom) that are detectible at certain wavelengths due to the absorption of infrared light. FTIR then produces a graph, known as an infrared spectrum, that depicts the covalent bonds as peaks. An analyst then compares the unknown substance’s graph to the infrared spectrum (graph) of a known substance (i.e., cocaine). This interpretation involves a human-conducted peak-to-peak comparison of the graphs’ overall appearance, physical properties, band width, functional group characteristics, as well as tests for carbonyls, aromatics, and multiple bonds.
GCMS is a combination of two techniques. The gas chromatograph technique separates the unknown compounds into ion fragments (i.e., the ionization process) and the mass spectrometer technique then uses a magnetic field to identify the composition of the ion fragments. The result is a graph, known as a mass spectrum, which depicts the ion fragments detected and identified in the GCMS. Like the FTIR process, a human compares the result of an unknown mass spectrum to known mass spectra (i.e., a hardcopy or e-copy library of spectra/graphs). To properly interpret the test results, a technician looks for a specific molecular ion (the highest molecular weight in the spectrum), and information-rich fragment ions, evaluating (among other things) the mass differences that must correspond to the ion fragments with realistic compositions.
Although FTIR and GCMS are very different identification techniques, their interpretation processes are similar and subjective. With both, it is important to establish the validity of the “known” substance(s) that will be used to compare against an “unknown” substance. The scientific term for the “known” substance is “reference material,” which is defined as material that is sufficiently homogeneous and stable with reference to specified chemical properties and has been established to be fit for its intended use in measurement/comparison. Reference material must be scientifically authentic and traceable. This means that proper documentation is necessary to show its specified property values and authenticity going back to a verified substance. Additionally, reference material needs to be evaluated using the same set of procedures,3 and under the same conditions, as the unknown substance’s testing. All the spectra generated from reference material testing with the FTIR and GCMS is stored in spectra libraries for comparison purposes.
By analogy, this drug-identification process is akin to comparing a latent fingerprint (i.e., an unknown solid or liquid) with a known inked fingerprint impression (i.e., a reference material like authentic cocaine). The validity of fingerprint analysis is based on the quality of the prints, on having a one inked fingerprint impression that verifiably comes from a known individual, and a skilled analyst. An inked fingerprint impression not “traceable” to a known human being is meaningless for comparison with other unknown fingerprint samples. The same is true with drug testing. The reference material must be adequately verified and traceable to a known standard in order to be of any value in comparison analyses.
CLD’s testing methods for drug analysis leave room for human error both in the way it maintains reference material and in how analysts compare known vs. unknown samples. Subjectivity also plays a roll in these comparison-based tests, which can have a major impact on results. Make sure you work with an attorney who understands the testing procedlisures and can identify errors when they happen.
1) A “technique” is the use of instrumentation to isolate, detect, and identify chemical substances.
2) A “method” is a set of laboratory-specific techniques to get qualitative and/or quantitative composition of a sample.
3) A set of approved laboratory-specific steps and criteria that document a validated analytical method (i.e., standard operating procedures).