Abstract
Illicit-drug production, trafficking and seizures are on an all-time high. This consequently raises pressure on investigative authorities to provide rapid forensic results to assist law enforcement and legal processes in drug-related cases. Ideally, every police officer is equipped with a detector to reliably perform drug testing directly at the incident scene. Such a detector should preferably be small, portable, inexpensive and shock-resistant but should also provide sufficient selectivity to prevent erroneous identifications. This study explores the concept of on-site drugs-of-abuse detection using a 1.8 × 2.2 mm2 multipixel near-infrared (NIR) spectral sensor that potentially can be integrated into a smartphone. This integrated sensor, based on an InGaAs-on-silicon technology, exploits an array of resonant-cavity enhanced photodetectors without any moving parts. A 100% correct classification of 11 common illicit drugs, pharmaceuticals and adulterants was achieved by chemometric modelling of the response of 15 wavelength-specific pixels. The performance on actual forensic casework was investigated on 246 cocaine-suspected powders and 39 MDMA-suspected ecstasy tablets yielding an over 90% correct classification in both cases. These findings show that presumptive drug testing by miniaturized spectral sensors is a promising development ultimately paving the way for a fully integrated drug-sensor in mobile communication devices used by law enforcement.
| Original language | English |
|---|---|
| Article number | 123441 |
| Number of pages | 8 |
| Journal | Talanta |
| Volume | 245 |
| DOIs | |
| Publication status | Published - 1 Aug 2022 |
Bibliographical note
Funding Information:This research was partially funded under Penta Call 2 project Environmental Sensors for AIR Quality (ESAIRQ) n. 16113, NWO TTW project n. 16670 and NWO Zwaartekracht Research Center for Integrated Nanophotonics.
Funding Information:
For the measurements in each set, three preprocessing methods were applied to the triplicate-averaged absorbance values, and compared: mean-centering, sum normalization and standard normal variate (SNV). Six classifiers were compared for building the classification model: linear discriminant analysis (LDA), partial least square ? discriminant analysis (PLS-DA), support vector machine (SVM), principal component analysis (PCA)-LDA, random forest (RF) and PLS-RF. Fivefold groupwise cross-validation was used to optimize the parameters of the PLS, PCA and RF-based models, and groupwise randomized search cross-validation was used to optimize the SVM models that had a larger number of parameters to tune. In all cases of cross-validation, replicate measurements from each sample were kept together in one group. The combination of the preprocessing method and classifier that resulted in the best prediction performance for each experiment set is shown in this manuscript. The algorithms used in analysis and modeling were implemented in Python using packages from NumPy [50], Matplotlib [51], and Scikit-learn [52].This research was partially funded under Penta Call 2 project Environmental Sensors for AIR Quality (ESAIRQ) n. 16113, NWO TTW project n. 16670 and NWO Zwaartekracht Research Center for Integrated Nanophotonics.
Publisher Copyright:
© 2022 The Authors
Funding
This research was partially funded under Penta Call 2 project Environmental Sensors for AIR Quality (ESAIRQ) n. 16113, NWO TTW project n. 16670 and NWO Zwaartekracht Research Center for Integrated Nanophotonics. For the measurements in each set, three preprocessing methods were applied to the triplicate-averaged absorbance values, and compared: mean-centering, sum normalization and standard normal variate (SNV). Six classifiers were compared for building the classification model: linear discriminant analysis (LDA), partial least square ? discriminant analysis (PLS-DA), support vector machine (SVM), principal component analysis (PCA)-LDA, random forest (RF) and PLS-RF. Fivefold groupwise cross-validation was used to optimize the parameters of the PLS, PCA and RF-based models, and groupwise randomized search cross-validation was used to optimize the SVM models that had a larger number of parameters to tune. In all cases of cross-validation, replicate measurements from each sample were kept together in one group. The combination of the preprocessing method and classifier that resulted in the best prediction performance for each experiment set is shown in this manuscript. The algorithms used in analysis and modeling were implemented in Python using packages from NumPy [50], Matplotlib [51], and Scikit-learn [52].This research was partially funded under Penta Call 2 project Environmental Sensors for AIR Quality (ESAIRQ) n. 16113, NWO TTW project n. 16670 and NWO Zwaartekracht Research Center for Integrated Nanophotonics.
UN SDGs
This output contributes to the following UN Sustainable Development Goals (SDGs)
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SDG 3 Good Health and Well-being
Keywords
- Forensic on-scene analysis
- Illicit-drug detection
- Indicative testing
- Integrated photonics
- Portable devices
- Spectral sensing
- N-Methyl-3,4-methylenedioxyamphetamine
- Cocaine
- Substance Abuse Detection
- Illicit Drugs
- Smartphone
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