U.S. flag

An official website of the United States government, Department of Justice.

Evaluation of Laser Diode Thermal Desorption (LDTD) for High Throughput Analysis of Controlled Substances and Toxicology in Forensic Sciences

NCJ Number
Date Published
January 2014
147 pages

This project evaluated laser diode thermal desorption (LDTD) coupled with triple quadrupole (QQQ) mass spectrometry for the high-throughput quantitative analysis of controlled substances and drug toxicology in forensic laboratories.


LDTD was determined to have potential for screening and quantifying biological samples in forensic laboratories. It can rapidly analyze a large number of samples in a short period (approximately 12 seconds per sample). This makes it ideal for high throughput forensic laboratories; however, due to the lack of chromatography, analysts must be diligent in developing their method, so as to determine the best parameters and extraction techniques. The specific advantages of the LDTD system are quick installation, little instrument training, no additional software requirement, ease of use, minimal maintenance, rapid sample analysis, minimal sample volume, lack of chromatographic solvents and consumables, and the ability to be used across multiple mass spectrometry platforms. The disadvantages of LDTD are sample destruction; inconsistencies associated with manual spotting; erroneous peaks due to interferences in sample matrix and peak apparitions as a result of the desorption process; difficulty in analyzing isomers and isobars due to the lack of chromatography; and the limited amount of ion transitions per method, depending on the mass spectrometry used. This project optimized 111 drugs of abuse in methanolic drug solutions. Forty-nine compounds across major drug classes were spiked into drug-free human urine and blood for validation of screening or quantitative analysis. Liquid-liquid extraction or solid phase extraction methods were used for both urine and blood matrices for the extraction of drug analytes of interest. The goal was to use minimal sample preparation in order to increase overall sample analysis efficiency. 27 figures and 34 references

Date Published: January 1, 2014