The identification of illicit drugs and related compounds often requires more than a single analytical technique. Established controlled substances may be recognized through conventional library searching, while emerging drugs, structural analogs, impurities, mixtures, and new psychoactive substances may not have an exact reference spectrum available. In these cases, reliable identification depends on combining complementary analytical data with systematic interpretation.
This webpage brings together several practical examples illustrating the use of electron ionization and chemical ionization GC/MS, accurate-mass measurements, DART mass spectrometry, infrared spectroscopy, and NMR. Each technique contributes different information, including molecular weight, molecular formula, functional groups, fragmentation behavior, and structural connectivity.
NIST Identity Search can provide rapid identification when a high-quality reference spectrum is present in the library. When an exact match is unavailable, NIST Hybrid Search can identify structurally related compounds by combining fragment-ion matching with neutral-loss information. This approach can greatly extend the practical value of existing spectral libraries and provide important clues about the structural class of an unknown.
Accurate-mass data and proposed molecular formulas can then be used with large “spectra-less” databases such as SciFinder/CAS Registry and ChemSpider. These resources contain millions of reported structures, including many compounds for which searchable mass spectra are unavailable. Candidate structures can be refined using no. associate references, key words, substructures, molecular formula, accurate mass, sample history, known chemistry, isotope patterns, and expected fragmentation.
This combined strategy reflects the “Known Unknown” philosophy: the compound may be unknown to the analyst, but it may already have been reported in the scientific literature, registered in a chemical database, or represented by a closely related compound in a spectral library. By integrating multiple tools and complementary evidence, analysts can move from a broad list of possibilities toward a scientifically defensible identification.
The four links below provide examples of these approaches applied to the identification of illicit drugs, white powders, PCP-related compounds, and new psychoactive substances.
-Illicit Drugs EI GC/MS Current Trends Symposium
-Seized Drugs Forensic@NIST2022 Workshop
-Identity of PCP Related Drug Hybrid Search
-Illicit Drug Identified Wiley KnowItAll Searches