Methods for impurity profiling of heroin and cocaine

12

Methods for impurity profiling of heroin and cocaine

4.

Trace elements (ICP-MS)

The resulting data are useful for:

(a)

Determining possible sample links;

(b)

Possible indication of origin for “uncut” samples.

5.

Isotopic abundance (isotope ratio mass spectrometry (IRMS))

The resulting data are useful for:

(a)

Determining possible sample links;

(b)

Indicating region of sample origin.

To aid the reader in assigning the significance of individual peaks in the chro-

matogram, table 1 of annex II summarizes many of the impurities that have been

identified in illicit heroin samples and gives, to the extent possible, an indica-

tion as to their “source”, that is, whether they are related to the plant material,

the manufacturing process, subsequent distribution or the analytical procedure

(artefacts). Table 2 of annex II summarizes the same information for samples of

illicit cocaine.

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13

III.

METHODS FOR IMPURITY PROFILING

A.

General comments

The methods discussed in this manual are provided as a general guide for the

interested reader. For those who wish to utilize any of these methods as part of

the establishment of profiling programmes for heroin and/or cocaine, it is advis-

able to study the original publications.* Not only will such study ensure that the

method selected will meet requirements, but most certainly the reader will gain

much additional practical and theoretical information. Quantification allows a more

rigorous basis for comparison, but frequently only qualitative data are used. The

recommended qualitative approach is to normalize the data by determining area

count ratios of the various detected impurities relative to the appropriate target

alkaloid (heroin or cocaine). It is the case that this method is actually more reli-

able for purposes of comparing samples, as both quantification errors and biases

from the introduction of adulterants and/or diluents are greatly reduced. 

Whatever the approach, it is essential that all methods, whether published in

this manual or in the scientific literature, be evaluated in the analyst’s own lab-

oratory prior to use.

After the Consultative Meeting held in Sydney, Australia, in 1999, a review

[16] and several other methods for heroin profiling, using mostly advanced sta-

tistical procedures for data evaluation, were published [17-28]. However, in terms

of analytical technique, publications since 1999, for the most part, still indicate

gas chromatography as the analytical tool of choice. 

For those who do decide to create an impurity profiling programme, it can-

not be overemphasized that the successful implementation of any programme

requires meticulous control of all analytical method and sample storage variables.

Additionally, it is the opinion of several experts in the field that instrumentation

utilized in an ongoing impurity profiling programme should not be used for any

other purpose. Finally, all procedures utilized for receiving, processing and stor-

age of samples for impurity profiling should adhere to good laboratory practice

and custodial evidentiary procedures. 

Impurity profiling results are typically used for court purposes (evidence, tac-

tical operations) and/or for intelligence purposes (strategic intelligence operations).

Since one rarely knows beforehand what samples will be used in an evidentiary

manner, the integrity of both the sample handling procedures and the analytical

*A few of the methods listed here have not been published previously and in those instances the

names of the source laboratory and a primary contact person are provided under the method heading;

contact details are available from UNODC.

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14

Methods for impurity profiling of heroin and cocaine

procedures must be maintained at the highest level. From an analytical standpoint,

it is clear that for all chromatographic methods the frequent incorporation of stan-

dard and “check” samples can be invaluable in helping to maintain the integrity

of the analytical product. As has already been noted, it is necessary for the ana-

lyst 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.

Needless to say, if impurity profiling results may ever be utilized as evi-

dence, then it is likely that some aspects of the impurity profiling procedure will

depend on court and/or legislative requirements. Irrespective of the approach uti-

lized, the importance of taking a comprehensive approach to this work cannot be

overemphasized. While it is true that the approach and the methods utilized by

the forensic chemist can be constrained to some degree by legal requirements,

typically the analyst still has a good deal of flexibility in the design of an impu-

rity profiling procedure. Finally, and most importantly, when linkage determina-

tions are performed for evidentiary purposes, it is quite clear that a positive

correlation cannot be based only on the results of a single method. In those cases,

the expert group recommends the additional use of other, preferably independent

methods, with at least one of those methods designed to access a trace level alka-

loidal fraction. An analysis of occluded solvents is always an excellent additio-

nal method and is very useful in the earlier stages of a comparative analysis;

however, solvent analyses are of secondary importance relative to analyses that

address the presence of plant-related constituents. Supplementary information is

provided in annex I.

B.

Heroin methods

Table 1 of annex II summarizes many of the major and trace level alkaloidal

impurities found in heroin, together with some common adulterants and diluents.

1.

Hydrolysis of heroin

Post-processing hydrolysis can occur readily for those samples containing non-

bound water or excess acid. In those cases where both the alkaloidal content and

the extent of hydrolysis are significant, the sample may become dark brown

(almost black) and will finally become tar-like. In less severe cases, hydrolysis

may not be obvious until the impurity profile data have been examined. An

O

6

-monoacetylmorphine (O6MAM) content greater than 10% relative to the heroin

is an indication that post-processing hydrolysis may have occurred in the sample.

Other indicators are very low levels of O

3

-monoacetylmorphine (O3MAM) and

relatively high morphine content (> 1% relative to the heroin). In some cases both

the morphine and the O6MAM can be present at a higher level than the heroin

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