Methods for impurity profiling of heroin and cocaine

Introduction

3

on the detection and assay of various groups of drugs in biological specimens,

can be requested from the Laboratory and Scientific Section (see address below).

Copies of articles from the scientific literature on drug characterization and impu-

rity profiling can also be requested from the same address.

It is important to note that these manuals are provided to laboratories as edu-

cational documents within the training remit of UNODC and as a means of encour-

aging laboratories to collaborate and participate with the United Nations in the

global effort to combat illicit drugs. In addition, these publications are also an

attempt to help promote national efforts by providing internationally accepted

guidelines.

C.

Use of the manual

The present manual, as was the case with previous manuals, suggests approaches

that may assist drug analysts in the selection of methods appropriate to the

sample under examination and provide data suitable for the purpose at hand. The

majority of methods described here are published in the scientific literature. They

represent a summary of the experience of scientists from several reputable labo-

ratories around the world and have been routinely used for a number of years in

those laboratories. The reader should be aware, however, that there are a number

of other published methods not mentioned in this manual that may also produce

acceptable results. There are a number of more sophisticated additional approaches

that may provide insight into specific aspects of sample history, but may not be

necessary for routine operational applications. Therefore, the methods described

here should be understood as guidance, that is, minor modifications to suit local

circumstances should normally not change the validity of the results.

Methods provided here are chosen on the basis of proven suitability and reli-

ability, important prerequisites, especially if the results are to be used for eviden-

tial purposes. However, the reader should be aware that the conclusions drawn

using different analytical methods will each have a different level of certainty.

Since similarity based on one method alone is usually not sufficient for eviden-

tial purposes and in order to make the overall process more rigorous, the expert

group recommends the use of at least a second method where each method used

addresses a different set of target analytes. However, the decision whether or not

additional methods are required remains with the chemist on a case-by-case basis

and may also be dependent on national requirements. As a guiding principle, the

rigorousness of the method employed determines the strength of the evidence 

produced. 

In this context, it should also be understood that drug profiling is not a rou-

tine analytical technique. Dedicated equipment and experienced chemists are

required and close cooperation between forensic laboratories and law enforcement

personnel is critical for effective use of results. 

For further details on the background and operational value, as well as lim-

itations, of drug characterization and impurity profiling, the reader is referred to

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4

Methods for impurity profiling of heroin and cocaine

the United Nations manual entitled Drug Characterization/Impurity Profiling:

Background and Concepts [5].

The Laboratory and Scientific Section would welcome observations on the

contents and usefulness of the present manual. Comments and suggestions may

be addressed to:

Laboratory and Scientific Section

United Nations Office on Drugs and Crime

Vienna International Centre

P.O. Box 500

1400 Vienna

Austria

Fax: [phone]

E-mail: [e-mail]

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II.

ASPECTS OF 

DRUG CHARACTERIZATION AND

IMPURITY PROFILING

A.

Background, concepts, purpose and strategies

Drug characterization and impurity profiling studies can be valuable scientific

tools to support law enforcement operations. As a general concept, when impurity

profiling is employed for sample comparisons (linkage determinations), all pos-

sible means for the generation of information and data should be considered,

including the use of physical characteristics, packaging, adulterants and diluents. 

In organic chemistry the term “characterization” is often utilized to describe

the process of determining the exact molecular structure of an organic compound.

However, here the term “drug characterization” is used to mean the process of

determining the major features of a drug sample, both its physical and chemical

characteristics, and also including the presence and nature of cutting agents, the

quantification of significant sample components and so on. In contrast, impurity

profiling typically involves several analyses that are designed to produce a detailed

picture (profile) of a drug sample, usually in the form of chromatographic data.

The resulting chemical profiles, also known as “signatures” or “impurity profiles”,

result in the identification and, usually, the quantification of major components

in the sample just as may also be accomplished in drug characterization. However,

unlike drug characterization work, impurity profiling will also include one or more

additional analyses designed to target the minor (trace) components in the sam-

ple.* When performing impurity profiling work, the analyst’s ultimate goal is to

obtain profiles of the major and minor components in formats that allow him/her

to use the data as a comparative tool for the purpose of locating other samples

having similar profiles.

An introduction to drug characterization and impurity profiling, its potential

and limitations is given in the United Nations manual Drug Characterization/

Impurity Profiling: Background and Concepts [5], which addresses both labora-

tory and law enforcement personnel who may wish to start an impurity profiling

programme. While the reader is referred to this United Nations manual, some of

the parts most relevant to the forensic chemist are the uses and the limitations of

the technique and these are discussed briefly below.

5

*For the purposes of this manual, major components are components present above 1% relative to

the target compound (heroin or cocaine), while minor components are generally below 1% relative to

the target compound and, in general, can be found only after an extraction or pre-concentration step.

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