methods for impurity profiling of heroin and cocaine - United Nations ...

Data handling, interpretation of results and data collections 49
bulk of the heroin and other alkaloidal bases are retained in the aqueous phase
while extracting many of the alkaloidal-related amidic compounds into an organic
phase. High-resolution capillary gas chromatograms of these extracts are typically
quite complex and many analysts have found that visual comparison of the
overlaid chromatograms is the most efficient direct comparison method (see annex
II, tables 1 and 2, for a listing of many of the known alkaloidal compounds found
in heroin and cocaine).
B. Interpretation of results
Irrespective of the equipment and software available in a laboratory carrying out,
or planning to carry out, impurity profiling, the results have to be interpreted carefully,
taking all relevant considerations into account, including analytical implications
of illicit processing and distribution, as well as those arising, for example,
from differences in storage conditions. Experience in the interpretation of profiling
results can only be built gradually, but good analytical skills and knowledge
of relevant chemistry are essential. In addition, for analytical results to be operationally
useful, they have to be communicated in an adequate way to the requesting
authority. The United Nations manual Drug Characterization/Impurity Profiling:
Background and Concepts [5] provides an overview of relevant practical aspects
related to the interpretation of results, addressing the following areas:
(a) The significance of chemical similarities and differences between
drug samples;
(b) Establishing specific links between two or more samples;
(c) Establishing drug distribution patterns;
(d) Identifying the source of drug samples:
(i) Natural and semi-synthetic drugs;
(ii) Synthetic drugs;
(e) Identifying and characterizing the specific starting materials employed
in clandestine drug manufacture.
C. Approach to setting up profiling data collections
As explained previously, the availability of appropriate databases is critical for
both types of comparison, case-to-case comparisons for evidential purposes and
retrospective comparisons for intelligence purposes. A recommended approach to
the compilation of a profiling data collection is as follows:
(a) Generate a data bank of comparison data (i.e. analytical data plus any
appropriate physical data). (The samples used for generating compari-