Methods for impurity profiling of heroin and cocaine

Methods for impurity profiling

39

2.

Methods for the determination of trace components

The methods described below are used to substantiate the results obtained from

methods C1-C4. A potential limitation for the methods D1 and D2, presented

below, is that they are designed for the analysis of unadulterated samples.

However, methods D3 and D4 are not limited to unadulterated samples, but they

do not employ a derivatization step and, as a result, artefact production is a con-

cern. In addition, many of the by-products and decomposition products generated

during cocaine processing are not observed unless the sample is derivatized.

Hence, it is likely that no one of these methods will be suitable for every labo-

ratory and/or for every sample.

Some researchers have observed that the truxillines and the corresponding

truxillic/truxinic acids may not be ideal parameters for profiling purposes owing

to what is thought to be trans-isomerization and/or artefact formation.* However,

Moore and others [50-52] examined this issue in detail and found no evidence to

support this view. Rather, Moore and others describe a truxilline analysis method

and state that the method results are very reproducible and very useful for indi-

cating the country of origin. On the matter of benzoic acid, however, there seems

to be general agreement that it may not provide a very useful parameter for either

sample-to-sample comparison or origin determination.

Temperatures:

Injector: 215° C

Detector: 325° C

Oven: 120° C, hold for 2 min, 6° C/min to 320° C, hold

for 5 min

Internal standard: None; normalize by peak area ratios for tropacocaine, norcocaine

and  cis- and trans-cinnamoylcocaine relative to cocaine.

Sample preparation: Weigh the equivalent of 30 mg of cocaine base and dissolve in

2 ml of absolute ethanol.

Rationale for use: Not the most sensitive method, but a broad range of nitrogen-

containing compounds can be detected (by the same token, the majority of nitrogen-

free adulterants and diluents cannot be detected). Simple sample preparation (no

extraction or derivatization) enhances sample throughput.

Outcome: Sample comparisons for discrimination and evaluation of samples for case-

to-case evidential purposes. Additional information is required to confirm links

between samples or to assign source regions, that is, the method should be used as

one part within a broader analysis scheme.

*Personal communication from Olivier Guéniat, Police de sûreté, Neuchâtel, Switzerland, at the

Consultative Meeting held in Sydney, Australia, in 1999; see also Rivier [53].

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40

Methods for impurity profiling of heroin and cocaine

Method D1:

GC method, with derivatization: “trimethoxy method”

Source:  J. F. Casale and J. M. Moore, “3’,4’,5’-Trimethoxy-substituted analogs of

cocaine, cis-/trans-cinnamoylcocaine and tropacocaine: characterization and quantita-

tion of new alkaloids in coca leaf, coca paste and refined illicit cocaine”, Journal of

Forensic Sciences, vol. 39, No. 2 (1994), pp. 462-472.

Operating conditions: 

Detector:

FID

Column:

DB-1 or equivalent, 30 m x 0.25 mm x 0.25 µm

Carrier gas:

Hydrogen at 35 cm/sec

Injection size:

2 µl, split 20:1

Temperatures:

Injector: 230° C

Detector: 280° C

Oven: 150° C for 1 min, 6° C/min to 275° C, hold for

8 min 

Internal standard: 3’, 4’, 5’-Trimethoxyethylcocaine at 0.1 mg/ml in chloroform

Sample preparation: 100 mg equivalent of cocaine base is added to 0.5 ml of inter-

nal standard solution and 0.5 ml of saturated aqueous sodium bicarbonate. Mix

thoroughly, allow the phases to separate and mix the chloroform layer into 0.5 gm of

Celite 545 and pack the Celite sample mixture onto the top of a previously prepared

ion-pairing column. Elute with 22 ml of water-saturated chloroform, discarding the

first 10 ml and capturing the remainder. Reduce to dryness and reconstitute in 1.0 ml

of chloroform for GC-FID analysis.

The ion-pairing column is prepared by packing a 0.5-ml saturated aqueous sodium

bicarbonate Celite 545 bottom layer followed by 2 ml of 1N HCl:2N NaCl in a 4-gm

Celite 545 top layer in a 260 x 22 mm glass column. The column is then primed by

eluting with 10 ml of water-saturated chloroform. 

Rationale for use: The ion-pairing column removes the vast majority of the cocaine

and thereby allows for the quantification of 3’,4’,5’-trimethoxycocaine (TMC,

MW 393), 3’,4’,5’-trimethoxytropacocaine (TMT, MW 335) and cis- and trans-

3’,4’,5’-trimethoxycinnamoyl-cocaine (TMCC, MW 419) in unadulterated cocaine

hydrochloride. When cocaine = 1.0, the approximate relative retention times are TMT

= 1.3, TMC = 1.65, cTMCC = 1.82, tTMCC = 2.1. Tropacocaine and norcocaine are

also easily detected by this method. 

Outcome: As with method D2, this is one of the methods that are necessary to dis-

tinguish between coca grown in different countries. It allows sample comparisons for

discrimination and evaluation of samples for case-to-case evidential purposes (linkage

determinations). Provides additional information required to confirm links between

samples, that is, the method should be used in conjunction with a major component

analysis.

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