10
Methods for impurity profiling of heroin and cocaine
data should be gathered from all available sources, that is, to include data on cut-
ting agents (adulterants and diluents), packaging methods and materials, logos and
fingerprints and, in short, all comparable information.
As noted above, there are significant limitations associated with origin deter-
mination work and, not surprisingly, there are also other equally important limi-
tations associated with linkage determination work. These limitations are due
primarily to the variable nature of the clandestine production processes, subse-
quent sample modifications during distribution and sample changes related to
widely varying transportation histories. Variations in processing impurities across
consecutive batches from a given laboratory have not been well studied, but it is
well known that such variations can be relatively large. Moreover, large illicit
consignments of cocaine and heroin rarely constitute the product of a single lab-
oratory operation. As a result, the analyst may be able to form an opinion as to
the likelihood that two samples are consistent with their being from two differ-
ent batches made in the same laboratory, but most often such a link cannot be
established with certainty. When the samples are from the same processing batch
and their locations in the distribution chain are close, then the probability that the
analyst will be able to link them with reasonable certainty is markedly improved,
but still not guaranteed. However, when two samples are not chemically related,
it is often possible for an analyst to state that fact with certainty.
Considering the previously noted limitations, it would be unrealistic to think
a sufficiently large information base of regional and/or international impurity pro-
filing data could be developed that would enable the identification of related sam-
ple seizures in large networks and/or major trafficking organizations. However,
with regard to smaller scale or local drug supply networks, impurity profiling data-
bases can be useful in a number of ways beyond the obvious establishment of
possible network linkages. One common such usage is to estimate the size of a
particular drug operation, which is information that can be used to estimate the mon-
etary value of the operation and, in turn, aid in the confiscation of financial assets.
C.
Types and investigational value of sample components
In general, the impurity profile of a drug sample reflects its history. For a drug
derived from a natural product, the history the analyst will attempt to measure
starts when the farmer selects the seed for planting and ends only upon the com-
pletion of all analytical work. As a consequence, impurities detected by an ana-
lyst can arise from many sources, but usually those impurities most easily detected
belong to one of the following four categories:
(a)
Compounds co-extracted from the raw plant materials;
(b)
Impurities and by-products to include occluded solvents and/or reagents:
(i)
Due principally to laboratory processing;
(ii)
Also contributed to by transportation and distribution practices;
Aspects of drug characterization and impurity profiling
11
(c)
Cutting agents added at any point in the distribution chain;
(d)
Analytical procedure-generated artefacts.
A number of laboratories throughout the world are at present involved in the work
of impurity profiling. Those laboratories do not all have the same purpose for this
work nor do all of the laboratories pursue the same “easily detected impurities”
(analytical targets). Following this paragraph is a listing of the most common ana-
lytical targets that these laboratories do pursue, two of which require the use of
relatively expensive analytical hardware not typically found in the majority of
forensic drug laboratories.
1.
Major components*
The resulting data are useful for:
(a)
Characterizing the target analyte heroin or cocaine;
(b)
Screening samples for possible linkages (similar samples);
(c)
Indicating region of sample origin;
(d)
Characterizing cutting agents (adulterants and diluents).
2.
Trace components**
The resulting data is useful for:
(a)
Determining possible sample links;
(b)
Indicating region of sample origin;
(c)
Indication of processing or synthetic methods utilized.
3.
Residual and/or occluded solvents
The resulting data are useful for:
(a)
Determining possible sample links;
(b)
Indicating region of sample origin (heroin only);***
(c)
Identification of “last-step” processing solvents.
*Major components are generally the most abundant alkaloids, diluents and adulterants.
**Analysis of trace components generally requires an extraction step and is most frequently fol-
lowed by a concentration step.
***For cocaine, the analysis of residual and/or occluded solvents may only indicate the region in
which the hydrochloride was produced, but not where the coca bush was grown.