Page 148 - Advances in Forensic Applications of Mass Spectrometry - Jehuda Yinon

1522_C03.fm Page 131 Thursday, November 13, 2003 9:53 AM

It is generally proposed that drugs can enter into hair by two processes:
adsorption from the external environment and incorporation into the grow-
ing hair shaft from blood supplying the hair follicle. Drugs can enter the hair
from exposure to chemicals in aerosols, smoke, or secretions from sweat and
sebaceous glands. Sweat is known to contain drugs present in blood. Because
hair is very porous and can increase its weight up to 18% by absorbing liquids,
drugs may be transfered easily to hair via sweat.
Drugs appear to be incorporated into the hair during at least three stages:
from the blood during hair formation, from sweat and sebum, and from
external environment.
From various studies, it has been demonstrated that after the same dos-
age, black hair incorporates much more of a drug than blond hair. This
2,3
has resulted in discussions about a possible racial bias of hair analysis and is
still under evaluation.
The possibility of racial bias due to differences in melanin concentrations
or in hair porosity is still under discussion. Melanins are responsible for the
color of hair. Two types of melanin are present: eumelanin (with low sulfur
content) and pheomelanin (with high sulfur content). Black and brown hair
contain more eumelanin than red and blond hair. It appears that it is not
simply the concentration of drugs in blood that determines the concentration
in hair. Numerous factors may influence the incorporation of drugs into hair,
such as the nature of the compounds (pKa, lipid solubility, and metabolism
pattern) and variation in hair growth cycles. Until these mechanisms are
elucidated, the quantitative results and extrapolation to the amount of drug
intake from such a hair analysis should be considered with extreme caution. 4

3.2 Procedures

3.2.1 Specimen Collection

Collection procedures for hair analysis for drugs have not been standardized.
In most published studies, the samples are obtained from random locations
on the scalp. Hair is best collected from the area at the back of the head,
called the vertex posterior. Compared with other areas of the head, this area
has less variability in the hair growth rate, the number of hairs in the growing
phase is more constant, and the hair is less subject to age- and sex-related
influences. Hair strands are cut as close as possible from the scalp, and the
location root-tip must be mentioned. Storage is achieved at ambiant tem-
perature in aluminium foil, an envelope, or a plastic tube. The sample size
varies considerably among laboratories and depends on the drug to be ana-
lyzed and the test methodology. For example, when nandrolone or
betamethasone is investigated, a 100 mg sample is recommended. Sample

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