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Sampling of illicit drugs for quantitative analysis--part III: sampling plans and sample preparations
T Csesztregi1, M Bovens2, L Dujourdy3
1Hungarian Institute for Forensic Sciences, P.O. Box 314/4, 1903 Budapest, Hungary.
Forensic Science International
|May 13, 2014
Summary
This study developed a sampling plan for analyzing illicit drugs like heroin, cocaine, and cannabis. It provides guidelines for sample size and increment number to minimize uncertainty in drug analysis.
Area of Science:
- Forensic Science
- Analytical Chemistry
- Materials Science
Background:
- Accurate quantitative analysis of illicit drugs is crucial for forensic investigations.
- Heterogeneity in drug samples presents significant challenges for representative sampling.
- Existing sampling methods may not adequately address the variability in common illicit substances.
Purpose of the Study:
- To devise a general sampling plan for the quantitative instrumental analysis of common illicit drugs.
- To establish recommended increment sizes and primary sample sizes for various drug forms.
- To minimize sampling uncertainty to match analytical uncertainty in drug seizure analysis.
Main Methods:
- Conducted drug homogeneity and particle size investigations.
- Developed a flow-chart-based general sampling plan for heroin, cocaine, amphetamine, cannabis resin, MDMA tablets, and herbal cannabis.
- Constructed a table correlating sampling uncertainty with the number of random increments and recommended increment sizes.
Main Results:
- A sampling plan was created for common illicit drugs, with specific recommendations for powdered drugs, cannabis resin, MDMA tablets, and herbal cannabis.
- Recommended increment sizes: 1g (powders/resin), 1 tablet (MDMA), 1 bud (herbal cannabis).
- Recommended primary sample sizes: 15x1g increments (powders/resin), 20 tablets (MDMA), 50 buds (herbal cannabis).
- Appropriate analytical sample sizes determined: 20-35mg (powders), 200mg (herbal cannabis).
Conclusions:
- The developed sampling plan helps laboratories minimize sampling uncertainty for illicit drug analysis.
- The study highlights the importance of comparing incremental sampling results to ensure a 'correct sample'.
- Recommended the use of control charts (R or S charts) for quality control in sampling procedures.
- The general sampling theory applied can be extended to other disciplines requiring correct sampling of powders and solids.