Analysis of Illicit Drugs in Human Biological Samples by LC-MS n - LC-MS in Drug Bioanalysis - page 387

Enzymatic Digestion
The keratin structure is destroyed through the use of proteolytic enzymes such as
pronase and proteinase K. They are often used with chemical agents such as urea
and thioglycolic to cleave the disulfide bonds and increase the dissolution rate of
enzyme activity. The extracting procedures, using enzymatic digestion, last about
4-6 h and must be conducted at constant temperature and pH for providing maximum
enzyme activity [ 155 ] .
Chemical Digestion
The hair treatment with concentrated solutions of sodium hydroxide allows the
complete dissolution of the keratin structure by chemical hydrolysis of proteins in
about 1 h. Under these conditions, some drugs such as amphetamines are volatile
and thus there may be losses of the analyte. In more basic solutions occurs the com-
plete hydrolysis of molecules such as cocaine, heroin, and 6-MAM [ 51 ] . Concentrated
solutions of hydrochloric acid are also used: it eliminates the problem of volatile
basic compounds, but increases the time of dissolution.
Matrix Solid Phase Dispersion
The matrix solid phase dispersion (MSPD) is a sample pretreatment technique used
for extraction of analytes from solid samples. Typically applications are found in the
treatment of complex biological matrices such as plant or animal tissues [ 156, 157 ] .
The solid phase particles, in addition to disperse the sample, break the structure of
the matrix, so that the contained analytes may be recovered. A cartridge is packed
with the homogenized mixture and placed between two filters, and then the elution
of the analytes is performed. This extraction technique allows for the use of small
amounts of sample, extraction of high yields, and reduced extraction times. Recently
the MSPD technique has been applied for the extraction of drugs of abuse from the
hair by Míguez-Framil et al. [ 144 ]. Hair samples (approximately 0.050 g) were
blended thoroughly with alumina in a glass mortar to obtain a homogeneous mix-
ture. The mixture was quantitatively transferred by using a powder funnel to a 10 ml
syringe. A previously conditioned Oasis HLB cartridge was then attached to the end
of the MSPD syringe for on column analytes retention. In this way, the target drugs
isolated from hair matrix were retained on column and adsorbed onto the solid sup-
port of the SPE cartridge.
Micropulverized Extraction
Miyaguchi and Inoue proposed micropulverized extraction for the determination of
amphetamine, methamphetamine, dimethylamphetamine, MDA, MDMA, ketamine,