On‐site forensic analysis of colored seized materials: Detection of brown heroin and MDMA‐tablets by a portable NIR spectrometer

Abstract

The increasing workload for forensic laboratories and the expanding complexity of the drug market necessitates efficient approaches to detect drugs of abuse. Identification directly at the scene of crime enables investigative forces to make rapid decisions. Additionally, on‐site identification of the material also leads to considerable efficiency and cost benefits. As such, paperwork, transportation, and time‐consuming analysis in a laboratory may be avoided. Near‐infrared (NIR) spectroscopy is an analysis technique suitable for rapid drug testing using portable equipment. A possible limitation of spectroscopic analysis concerns the complexity of seized materials. NIR measurements represent composite spectra for mixtures and diagnostic spectral features can be obscured by excipients such as colorants. Herein, a NIR‐based (1300–2600 nm) detection of heroin and MDMA in colored casework (i.e., brown powders and ecstasy tablets) using a portable analyzer is presented. The application includes a multistage data analysis model based on the net analyte signal (NAS) approach. This identification model was specifically designed for mixture analysis and requires a limited set of pure reference spectra only. Consequently, model calibration efforts are reduced to a minimum. A total of 549 forensic samples was tested comprising brown heroine samples and a variety of colored tablets with different active ingredients. This investigation led to a >99% true negative and >93% true positive rate for heroin and MDMA. These results show that accurate on‐site detection in colored casework is possible using NIR spectroscopy combined with an efficient data analysis model. These findings may eventually help in the transition of routine forensic laboratories from laboratory‐based techniques to portable equipment operated on scene.

Portable NIR spectroscopy: the route to green analytical chemistry

“…Illicit-drug seizures are a growing problem since the forensic drug identification is not easy to perform, especially in case of new psychoactive substances. Kranenburg and coworkers ( Kranenburg et al, 2022a ; Kranenburg et al, 2022b ; Kranenburg et al, 2022c ) and Awotunde and coworkers ( Awotunde et al, 2022 ) introduced a handheld NIR with a 1,300–2,600 nm range. A specific chemometric model was developed for forensic samples.…”

Rapid and On-Scene Chemical Identification of Intact Explosives with Portable Near-Infrared Spectroscopy and Multivariate Data Analysis

“…These samples were acquired as part of criminal investigations and are thus fully realistic and representative of the chemical complexity and diversity encountered in forensic practice. The advanced data analysis framework recently developed by TIPb data scientists to identify drugs of abuse in street samples [38] was used as a starting point to develop a tailor-made data analysis interface for NIR-based forensic explosive analysis. This involved the creation of a matrix library (Table S2, Supplemental Information), the construction of an LDA model for compound selection, and the creation of a NAS model to match a composite spectrum to the actual NIR data for an unknown sample.…”

“…Previously, this setup was successfully applied to identify and characterize an extensive set of frequently encountered drugs of abuse. High accuracy was achieved using a multi-stage chemometric model, which included a linear discrimination analysis (LDA) component and a net analyte signal (NAS) model [36][37][38][39][40]. To address the chemical diversity in the field of forensic explosive investigations, the data analysis strategy was further refined through a three-stage approach.…”

A green methodology for the determination of cocaine in camouflaged samples

“…Thus, Raman spectroscopy has been used for qualitative and quantitative analysis of abused drugs. [22][23][24][25] NIR spectroscopy has been also used for the determination of heroin and cocaine in seized street samples 20,26,27 or the direct quantication of cocaine in impregnated materials. 13 MIR spectroscopy, especially using attenuated total reection (ATR), has not only been employed for the direct discrimination and identication of cocaine and its adulterants in different types of seized samples 7,22,[28][29][30] but is also used for quantication using chemometrics.…”