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Technical Note – Microcrystal Tests

NCJ Number
Date Published
December 2023
7 pages

This publication is a technical note to the white paper Evolving Approaches and Technologies for Seized Drug Analysis” describing microcrystal tests.


This technical note to the white paper Evolving Approaches and Technologies for Seized Drug Analysis” provides an in-depth explanation of microcrystal tests, which provide a rapid and inexpensive alternative to instrumental analysis techniques through the development of unique crystal formations between a given analyte and a specific reagent. The unique microcrystals can be compared against a reference/control using a polarized light microscope (PLM) to assess crystal shape, size, color, and spatial arrangement. The inclusion of specific optical properties such as refractive index, birefringence, and sign of elongation adds additional support for the presence of a controlled substance(s) in a seized drug sample. Although the application of microcrystal tests to the analysis of seized drugs is not novel, the evolution of microcrystal tests and their application to the analysis of seized drugs is important given the current challenges of seized drug analysis. In particular, the ability to rapidly identify even minute quantities of relatively common seized drugs provides great value to forensic laboratories. Even though microcrystal tests have a relatively limited scope of analysis (i.e., common seized drugs), they are quick, sensitive, and inexpensive alternatives to advanced analytical techniques such as gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). Analyzing common drugs of abuse with microcrystal tests enables laboratories to dedicate more advanced instrumentation to more challenging seized drug samples. Microcrystal tests may also be incorporated into a validated analytical scheme to confirm the presence of controlled substances identified with alternative techniques.

Date Published: December 1, 2023