Methods for impurity profiling of heroin and cocaine



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8

Methods for impurity profiling of heroin and cocaine

all minor by-products, are the processing methods employed in the conversion of

the raw plant product to a street-ready product. Isotopic abundances are also

strongly affected by processing; however, isotopic abundance measurements are

the only validated method that can actually relate a specific sample to a specific

geographical origin. Processing issues apply equally to the illicit products of heroin

and cocaine; however, heroin profiling is further complicated by the additional

synthetic step required to convert the morphine into heroin. 

Isotopic abundance and trace element measurements are not widely available

to the forensic analyst owing in part to the cost of the hardware and in part to

the significant training requirement mandated by the techniques. More frequently

the forensic analyst will use chromatographic techniques for impurity profiling

that target major alkaloids, minor alkaloids, processing by-products, adulterants

and diluents, and occluded solvents. As noted previously, it is important to under-

stand that these techniques only provide information that is indirectly related to

a specific geographical origin. When using chromatographic techniques, too, it is

important to understand that, in general, there is a direct and inverse relationship

between the quality (purity) of the sample and one’s ability to associate that sam-

ple with a specific geographical origin or to establish definitive linkages between

two or more samples (i.e. the more highly refined or the more highly diluted a

sample, the more difficult it becomes to detect components other than the major

alkaloids; hence, the number of comparison points are reduced).

The fact that the relative ratios of the major alkaloids in opium and coca leaf

are closely associated with plant varietal, cultivar and agronomic differences can

be exploited for the assignment of geographical origin. It is the case that a sig-

nificant portion of the illicit opium poppy grown shows relatively little varietal

or cultivar variation within each major growing region, while varietal or cultivar

variation between the major growing regions can be significant. For instance,

opium poppy cultivated in the Americas is quite distinct both morphologically and

chemically from opium poppy grown in Asia. However, most of the illicit coca

bush grown is Erythroxylum coca v. coca, with the illicit cultivation of other vari-

eties being limited mostly to Colombia. Hence for cocaine, it is possible that the

environmental differences existing between the various coca bush growing regions

of South America may be the most significant influence as regards both trace

level alkaloid content and 

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C and 



15

N abundance. For both cocaine and heroin,

the processing methods employed are most often region-specific and, in many

instances, differ quite substantially from one source region to the next. Therefore,

in the absence of post-processing hydrolysis, the quantities of alkaloidal con-

stituents as compared with the primary alkaloid (i.e. cocaine and heroin) and the

processing by-products found in the “street” product are primarily a function of

the processing methods employed by the clandestine laboratory, the source plant

species, variant or cultivar grown and, perhaps, agronomic differences. 

It has been successfully demonstrated that, when suitable authentic databases

are at hand, samples of seized cocaine can be related to relatively specific grow-

ing regions. For instance, Ehleringer and others [15] have successfully related

cocaine samples to the growing regions of the Guaviare and Putumayo-Caqueta



Aspects of drug characterization and impurity profiling

9

areas of Colombia, the Apurimac valley and the Huallaga-Ucayali valleys of Peru

and the Chapare valley of Bolivia. This work was accomplished using isotopic

abundance measurements in conjunction with chromatographic methods targeting

both major and minor alkaloid impurities, and occluded solvents. For cocaine, the

use of occluded solvent data does not provide information about the growing

region; however, it does allow for a distinction to be drawn about the region where

the cocaine was processed into the hydrochloride salt.

Unfortunately, such precise results are not at present available for determi-

nation of the origin of heroin samples. This is because of two limitations inher-

ent in work on heroin origin determination. One of those limitations is the

additional synthetic step that is required for converting morphine to heroin, as this

process obscures much of the minor alkaloid information. The second and per-

haps most important limitation is the very large number of authentic samples

required from frequently inaccessible growing and processing sites. For heroin,

the acquisition of such a large number of authentic samples is as yet beyond any

practical scope of work. Nevertheless, practical experience has shown that a large

percentage of heroin samples can be assigned to general regions of origin. Those

regions of origin are reasonably well known and are four not well-defined areas

best designated as South-West Asia, South-East Asia, Mexico and South America,

principally Colombia. 

Origin information for heroin and cocaine may also be derived from other

law enforcement information. However, since traditional law enforcement infor-

mation sources are frequently anecdotal in nature and/or inferred from other rela-

ted information, origin determination by scientific studies can be invaluable in

negating or confirming such information.



2.

Establishing trafficking and distribution networks

Although the same analytical tools can be employed for both work on origin deter-

mination and the elucidation of trafficking and distribution linkages, there exists

a quite different set of data handling requirements. Obviously impurity profiling

used for the purpose of establishing trafficking and distribution linkages does not

require the existence of an origin-related authentic database. Additionally, impu-

rity profiling for origin determination requires that the analytical data from a sin-

gle sample be correlated to one of several large groups of samples that exhibit

similar features where those features can be related to geographical origin, while

the successful determination of a trafficking linkage requires that the analytical

data generated from no less than two samples must share a significant number of

essentially identical features. The ideal case for a positive linkage determination,

of course, is when all measurable features of the comparison samples are identi-

cal. Although rare, it is possible for the data utilized in a successful linkage deter-

mination to be derived from relatively few sample-specific features regardless of

when or where the features were introduced into the sample, as long as the fea-

tures are sufficiently unique. However, in order to maximize the probability of

successful linkage determinations, it is strongly recommended that comparison




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