Fast analysis of narcotic drugs by optical chemical imaging

https://doi.org/10.1016/S0022-2313(02)00489-1Get rights and content

Abstract

A new technique is proposed for fast detection, identification and imaging of narcotic drugs in their solid phase. This technique, which requires only a tiny sample of a few microns, is based on microscopic chemical imaging. Minor sample preparation is required, and results are obtained within seconds. As far as we know, this is the most sensitive detection system available today for solid drugs. The technique can be applied for fast analysis of minute drug residues, and therefore is of considerable importance for forensic applications. It is shown that identification of drug traces in realistic matrixes is possible. Two main methods were applied in this study for detection of drugs and drug derivatives. The first method was based on direct detection and chemical imaging of the auto-fluorescence of the analyzed drugs. This method is applicable when the analyzed drug emits fluorescence under the experiment conditions, such as lysergic acid diethylamide (known as LSD). The second method was used for obtaining chemical imaging of drugs that do not fluoresce under the experiment conditions. In these cases fluorescent labeling dyes were applied to the examined samples (including the drug and the matrix). Both methods are simple and rapid, and require minor or no sample preparation at all. Detection limits are very low in the picogram range.

Introduction

Detection of drug traces is of considerable importance for forensic applications. Traditional drug analysis requires a rather large sample and is time-consuming. The ideal analytical tool for forensic applications should be fast and of very low detection limits. Therefore, a good analytical approach to this problem should be based on luminescence, which usually results in fast and simple detection methods. The applications of luminescence in drug analysis can be divided roughly into two major methods: solution and solid surface luminescence. Clearly, the later method is favored since it does not involve extraction of the sample and the consequent analyte dilution.

Several previous attempts of performing drug analysis based on solid surface luminescence have been published [1], [2]. In a recent work, near-IR spectroscopy was applied for identification and quantification of narcotics in solid mixtures [3]. However, these methods require rather large samples and their absolute detection limits are too high for most forensic applications.

An alternative approach, based on microscopic chemical imaging providing spectral information at every pixel, is proposed here. It has the potential of solving the issue of fast and very sensitive detection of drugs. Chemical imaging is a new science that develops the tools for “chemical vision” and its applications. These tools combine the analytical power of traditional spectroscopy with two-dimensional (2D) visualization. It means that one obtains a 2D image of an object with full spectrum at each of its pixels. It provides information on chemical composition with spatial resolution. This technology, which is based on Fourier-transform fluorescent imaging, can be coupled to microscopy for obtaining better absolute detection limits. The Fourier-transform fluorescent imaging microscopy (FTIM) method, developed in our laboratory [4], [5], provides microscopic images of the particulates of interest, with full fluorescence spectrum at each pixel.

In this study we show that FTIM enables direct microscopic inspection of solid drugs, with superb sensitivity. Two detection methods are suggested, which cover a wide range of possible applications. We also address the analytical problems due to matrix effects and present a method that handles many realistic matrixes. As far as we know, no alternative solution to the problem of direct microscopic drug analysis is available today.

Section snippets

Materials

The following drugs and drug derivatives were examined:

  • 1.

    lysergic acid diethylamide (LSD);

  • 2.

    cannabinol (CAN) and cannabidiol (CAND)—both materials are present in Cannbis sativa plant and belong to cannabinoids substances;

  • 3.

    ethylmorphine (EtMOR), also called morphine ethyl ether, is a derivative of morphine; and

  • 4.

    benzoylecgonine hydrate (BEC), which is a cocaine-related product.

All the above materials were purchased from Sigma-Aldrich, Israel, Ltd.

The following fluorescence labeling materials, purchased

Results and discussion

As previously mentioned, the ability of analyzing trace amounts of narcotic drugs in their original solid phase is of considerable forensic importance. We developed two methods for detection of drugs and drug derivatives. The first one was based on direct detection and chemical imaging of the auto-fluorescence of the analyzed drug, while the second method included a fluorescent-labeling step, performed prior to analysis. The second method is somewhat similar to recent analytical achievements

Conclusions

The above results clearly demonstrate the feasibility of fast analysis of narcotic drugs by fluorescence chemical imaging. Although best performance could be achieved using an imaging instrument of variable excitation wavelength, a low-cost setup (fixed excitation) can be applied in combination with a proper fluorescence labeling technique. Labeling of drugs in various matrixes was performed, which resulted in good FTIM detection. We found such labeling compounds that possess significant shift

Acknowledgements

This study was supported, in part, by the Mitchell Entrepreneurial Award and by The James Franck Program in Laser Matter Interaction.

V.B. is grateful for financial support by Ministry of Absorption for new immigrant scientists.

References (6)

  • S. Hassoon et al.

    Anal. Chim. Acta

    (2000)
  • R.J. Hurtubise, Solid Surface Luminescence Analysis, Theory, Instrumentation, Applications, Marcel Dekker, New York,...
  • E.P. Gibson

    J. Forensic Sci.

    (1977)
There are more references available in the full text version of this article.

Cited by (8)

  • Fourier transform spectral imaging microscopy (FT-SIM) and scanning Raman microscopy for the detection of indoor common contaminants on the surface of dental implants

    2015, Talanta
    Citation Excerpt :

    Several techniques have been developed and validated for analysis of aerosols adhered to surfaces, including fluorescence [14,15] and multiphoton ionization [16]. When surface imaging is of interest, Fourier Transform Spectral Imaging Microscopy (FT-SIM) [17–24] and Raman spectroscopies are known to provide detailed chemical information [25,26]. Some of these methods have the capacity to provide important information about characteristics of oral hard and soft tissues [27–30].

  • Is sensing spatially distributed chemical information using sensory substitution with hyperspectral imaging possible?

    2012, Chemometrics and Intelligent Laboratory Systems
    Citation Excerpt :

    The spectra can be subjected to various multivariate methods in order to extract chemical information. Hyperspectral cameras originated in the field of remote sensing [3] and are increasingly being used in many other scientific disciplines, such as chemistry [4,5], biology [6,7], medicine [8,9] and forensic sciences [10,11] because they provide an intuitive, easy and rapid way to detect various properties and compounds on surfaces. Chemical images generated from hyperspectral cameras can of course be viewed on a computer monitor for inspection, however in many applications it is awkward and cumbersome to switch ones attention to a monitor.

  • Ultra-trace analysis of illicit drugs from transfer of an electrostatic lift

    2011, Science and Justice
    Citation Excerpt :

    However, the actual application of these techniques is still a tedious detailed analytical process requiring a good deal of time for sample cleanup and preparation along with a suitable amount of time to complete analysis. Other improvements made in ultra-trace drug analysis that will emphasise immediacy with accuracy include such techniques as optical chemical imaging [11]. Solid surface luminescence of minute drug amounts from matrices can be achieved.

  • Fast optical assessment of pesticide coverage on plants

    2007, Analytica Chimica Acta
    Citation Excerpt :

    We suggest a new method for overcoming the above-mentioned matrix effects, which is based on inspecting the spectral influences resulting from the interaction of the pesticides and an added labeling compound. The detection is carried out by traditional LIF, which provides fast results [13,14,10,15] or by chemical mapping methods, such as Fourier transform chemical imaging [16–18]. A variety of commercial pesticides were examined in this study.

View all citing articles on Scopus
View full text