Marijuana and the Cannabinoids

188 Foltz
NaOH (1–2 N) at 80–95°C for 10–30 minutes (61–65,67) or maintained at 37°C overnight
(66). If the assay includes determination of drugs that are degraded in the presence
of strong alkali, β-glucuronidase/arylsulfatase can be used to digest the hair prior
to extraction (60).
Early methods for the determination of cannabinoids in hair used liquid/liquid
extraction to remove cannabinoids from the hydrolyzed hair (61–63,66,68); for example,
after acidification, homogenized hair can be extracted with hexane:ethyl acetate (9:1
v/v; ref. 61). A more recently published method employing enzymatic hydrolysis used
a two-step liquid/liquid extraction procedure (60). After adjustment of the pH to 8.5,
the hydrolyzed hair sample was extracted with chloroform:isopropanol (97:3 v/v).
The aqueous layer was separated, acidified with acetic acid, and re-extracted with
hexane:ethyl acetate (9:1 v/v). The two organic extracts were then combined and prepared
for GC/MS analysis.
Sachs and Dressler developed a very sensitive but lengthy assay for the detection
of THCA in hair. The procedure involved initially extracting the hydrolyzed hair in
hexane:ethyl acetate, washing the organic extract with 0.5 M NaOH and then with 0.1 M
HCl, and injecting the concentrated organic extract into a high-performance liquid chromatography
column. The fraction containing THCA was collected, acidified with 0.05
M phosphoric acid, and extracted with hexane:ethyl acetate. This extensive clean-up
permitted detection of derivatized THCA at concentrations as low as 0.3 pg/mL (67).
Other recently published methods have generally used SPE procedures, including
solid-phase microextraction (SPME). Moore et al. used mixed-mode hydrophobic/anion
exchange SPE cartridges to extract THCA from digested hair (64). After conditioning
the SPE cartridge, the hydrolyzed hair sample was added to the cartridge; the column
was washed with deionized water (2 mL) and 0.1 M HCl:acetonitrile (70:30 v/v; 2 mL)
and dried, after which THCA was eluted with 3 mL of hexane:ethyl acetate (75:25 v/v).
Several variations of solid-phase microextractions have recently been used to
extract cannabinoids from hydrolyzed hair samples. Strano-Rossi and Chiarotti developed
a relatively simple and rapid method for detection of THC, cannabinol, and cannabidiol
in hair based on solid-phase microextraction and GC/MS analysis (65). A
commercially available 30-µm polydimethylsiloxane fiber was dipped into the neutralized
hair digest for 15 minutes and then inserted directly into the injection port of
the GC/MS, where the adsorbed nonderivatized cannabinoids were vaporized. The
injection port temperature was 260°C; the 5% phenylmethylsilicone capillary column
was maintained at 100°C for 2 minutes and then temperature-programmed to 270°C.
The LODs for analysis of 50 mg of hair were 0.1 ng/mg for THC and cannabinol and
0.2 ng/mg for cannabidiol.
Musshoff et al. used two variations of a headspace solid-phase microextraction
(HS-SPME) method for determination of cannabinoids in hair. With one method a
100-µm polydimethylsiloxane fiber was inserted for 25 minutes into the headspace of
a heated (90°C) vial containing the digested hair (69). The fiber was then exposed to
the headspace in a second vial containing 25 µL of MSTFA for 8 minutes at 90°C,
resulting in trimethylsilylation of the adsorbed cannabinoids. Finally, the fiber was
inserted into the heated (250°C) injection port of a GC/MS, permitting the derivatized
cannabinoids to be vaporized and analyzed. The reported LODs ranged from 0.05 to
0.14 ng/mg for THC, cannabidiol, and cannabinol. THCA was not detected.