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

50 Methods for impurity profiling of heroin and cocaine
son data will depend on the purpose of the profiling work: it will be
day-to-day casework samples for a programme focusing on case-to-case
comparisons or a collection of appropriate samples from known sources
for a focus on determining sample origin);*
(b) Determine those data points collected within the data bank which have
statistically useful comparison value;
(c) Develop a search algorithm to identify possible “matches”. (Typically
either a relational database or spread sheet program is utilized. A simple
search algorithm using peak area ratios of two to four of the statistically
useful major components will keep the search times to a minimum
and may be sufficient for this work);
(d) Develop an enhanced search algorithm to extend comparison to other
statistically useful data points to include trace alkaloid-related components.
(As a first step in developing a profiling programme, comparison
of trace impurity profiles can be carried out by visual superimposition
of chromatograms);
(e) Develop and define a statistically defensible method for determining the
probability that “matches” are made correctly. (The use of a commercially
available statistical software program can greatly simplify this
process).
Any database should be periodically re-evaluated to identify obvious outliers and
to ensure its appropriateness for the intended purpose.
The process of building appropriate databases may be efficiently assisted by
the exchange of information and data, in a standardized form, between laboratories.
In conclusion, the methods and approaches published in this manual provide
guidance for the establishment of profiling programmes for heroin and/or cocaine.
As has already been noted, it is necessary for the analyst to understand exactly
how the impurity profiling results will be utilized and to know the precise nature
of all applicable requirements before attempting to set up an impurity profiling
programme and/or choosing the appropriate analytical methods. Irrespective of the
purpose, the importance of taking a comprehensive approach to profiling work
cannot be over emphasized.
*The accuracy of sample source assignments directly determines the limits of accuracy and quality
of the profiling programme.