Methods for impurity profiling of heroin and cocaine

24

Methods for impurity profiling of heroin and cocaine 

result of changes in electro-osmotic flow, which in turn results in an improvement in

resolution over time. A chromatogram taken from Lurie and others [35] showing a

typical separation obtained with a selection of basic compounds frequently found in

heroin samples and a table showing the corresponding relative migration times for

these and additional compounds appear in annex III as figure II and table 1.

Outcome: Indication of general source region (South-East Asia, South-West Asia,

Mexico, South America). Sample comparisons for discrimination and evaluation of

samples for case-to-case evidential purposes (linkage determinations). Additional infor-

mation 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.

Method A6.2:

Miscellar Electrokinetic Chromatography (MEKC)

Sample type: Major weakly basic, acidic and neutral components: cut and uncut samples.

Operating conditions: Agilent model HP

3D

CE

MEKC:

Column maintained at 15° C with an applied potential of

8.5 kV

Detector:

UV diode array

Monitored wavelength: 195 nm

Column:

32 cm x 50 µm fused silica (23.5 cm to detector window)

Run buffer:

103.2 mM sodium dodecylsulfate in 50 mM dibasic phos-

phate-borate buffer (pH 6.5)*

Injection solvent: 2:8 mixture of methanol and 3.75 mM monobasic sodium

phosphate buffer adjusted to pH 2.6 with phosphoric acid

Injection: 100 

mbar*s

Initial column conditioning: Flush with 0.1M NaOH, then with water, then with

CElixir reagent A and then with 50 mM phosphate-borate buffer (each flush for one

minute). Finish with a six-minute run buffer flush. 

Pre-injection column conditioning: Flush for two minutes with run buffer. 

External standards: Accurately weigh approximately 10 mg of the appropriate stan-

dard material for each target analyte into a 100-ml volumetric flask. Dilute to volume

with injection solvent. Assure dissolution before diluting to final volume. Sonication

for 15 minutes is recommended.

Sample preparation: Use the sample prepared from the CZE run.

Reference chromatogram: see annex III, figure III and table 2.

*In the original reference, the run buffer was obtained from MicroSolv Technology, Eatontown,

New Jersey, United States.

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Methods for impurity profiling

25

Rationale for use: A highly selective and rugged method that provides good quanti-

tative accuracy and precision. As noted above the costs associated with the method

are relatively low. Analyses times are short, resulting in a method capable of high

sample throughput. Effective mobilities are very reproducible, but increases in absolute

migration times are observed over time. The effect occurs owing to changes in electro-

osmotic flow, which in turn results in an improvement in resolution over time. Sugars

are not detected. A chromatogram taken from Lurie and others [35] showing a typical

separation obtained with a selection of weakly basic, acidic and neutral compounds

found frequently in heroin samples and a table showing the corresponding relative

migration times for these and additional compounds appear in annex III as figure III

and table 2.

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

to-case evidential purposes (linkage determinations). Additional information is required

to confirm links between samples, that is, the method should be used as one part with-

in a broader analysis scheme.

3.

Methods for the determination of trace components

Methods described in this subsection are used to substantiate the results of the

methods for the analysis of major components described above. 

All of the methods described below are designed for high-resolution capil-

lary GC and employ a liquid-liquid extraction step to isolate the acidic and neu-

tral components from the bulk basic fraction. The resulting extract produces an

analytical product that can be quite complex. It is not uncommon for the acidic

and neutral components extracted from a South-West Asian crudely refined heroin

base sample to yield a 250+ component high-resolution GC chromatogram.

Only a relative few of these compounds have been fully characterized [34, 36-39].

The most significant chemistry underlying the generation of a majority of these

250+ compounds is found in the works of Polonovski and Polonovski and of

Mariella and the associated papers [40-46].

The routine application of a computer algorithm for the comparison of such

complex data sets is not present in many laboratories. Rather, in those laborato-

ries lacking the appropriate computerized comparison capabilities, comparison of

trace impurity profiles is carried out by (visual) superimposition of chromatograms.

Virtually every manipulation of a sample carries with it some risk of sam-

ple degradation and, even in the hands of the most meticulous analyst, some sam-

ple degradation often occurs during an analytical process. For instance, two

common sources of degradation are contact with acid during the extraction process

and interactions with glass surfaces. When in the hands of a competent analyst,

degradation of a neutrals extract is typically not noticeable when the extract con-

tains at least 500 micrograms of total material. However, when the total amount

of extracted material is decreased significantly, as would be the case with highly

refined samples, then sample degradation during analysis becomes much more

of a concern. An example would be an extract obtained from a 50-mg sample

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