ICP-MS Method Validation for the Analysis of Trace Elements in Illicit Heroin

Abstract

The analysis of the trace elements present in the street doses of heroin has currently been undertaken with a dual aim: to estimate the elemental compositions and to cluster the case samples. Inductively coupled plasma-mass spectrometry was optimized to quantify 18 trace elements simultaneously. The method presented high repeatability and reproducibility for the target elements. The linear concentration ranges achieved linearity with r² > 0.9975. The limits of detection (LOD) were sufficiently low for almost all the elements except for Ca (LOD = 100 ppb). The limit of quantification (LOQ) for each element was also found acceptable. All target elements show mean recoveries between 92%–108%. Other major findings of this study including intra-sample (RSD < 5%) and inter-sample (RSD < 14%) precisions, sample weight test (≥30 mg), dissolution vessels, and sample filtration are also reported. The capability of the optimized method was assessed by using forty case samples. With their elemental compositions statistical classification of these case samples is also discussed herein.

Keywords:

• Heroin
• ICP-MS
• Profiling
• Trace elements
• Validation

Acknowledgments

The authors would like to thank the University of Malaya for the IPPP (PS360/2010A) grant, and facilities supplied by the Department of Chemistry Malaysia (MOSTI) to carry out this project. We are also indebted to Leethavani Balachandran (MOSTI) for her technical assistance.

Notes

*Major elements in parentheses at 10 ppm, minor elements at 0.1 ppm, and Hg at 0.005 ppm.

^#Major elements in parentheses at 5 ppm, minor elements at 0.05 ppm, and Hg at 0.0025 ppm.

^{^}IS was maintained at 0.01 ppm. Individual signal relative to IS is used for concentration calculation. Each IS is responsible for different groups indicated by its suffix I to IV.

ND ˭ Not detected or <LOD.

Note: Figures in bold indicate unacceptable RSD defined by Myors et al. (1998).

ND ˭ Not detected or <LOD.