Biomedical Engineering Reference
In-Depth Information
water-0.1 % formic acid and acetonitrile-0.1 % formic acid. When possible, the
authors performed sectional analysis of hair samples [
130
] . Wang and coworkers
used small volume LLE to perform cleanup after chemical hydrolysis of 20 mg of
hair sample with NaOH [
159
]. Targeted analytes in this work were amphetamine,
methamphetamine, MDA, MDMA. Digested hair were centrifuged, then 50 m l of
chloroform and a small amount of solid KCl were added, finally the mixture was
vortexed and centrifuged. Authors selected chloroform as extraction solvent because
of its greater density than water, allowing it to remain at the bottom of a tapped vial,
convenient when handling small volume. Authors tested volume of extraction sol-
vent ranging from 20 to 200 ml: results showed that smaller the volume used in the
extraction, the higher was the extraction of drugs. Although in this case the analysis
is performed by GC, this LLE approach is interesting.
11
Conclusion
The versatility offered by LC, i.e., the possibility to vary mobile phase composition
by adding suitable additives, as well as different types of commercially available
stationary phase, makes LC particularly appropriate for multiclass analysis of drugs
in complex matrices such as human biological matrices. Detection in MS and MS/
MS has amplified the advantages, allowing the technique to reach unambiguous ana-
lytical data. This makes the
odd coupled
LC-MS an analytical technique applicable
for forensic purposes, as the determination of illicit substances or substances sub-
jected to government regulations. Drugs of abuse are certainly substances of interest
in forensics and their determination in human biological matrices is a significant
analytical problem. The most common are hallucinogenic substances such as THC,
psychostimulants such as cocaine, amphetamines, and methoxyamphetamine or their
derivatives, but also other psychotropic substances of emerging abuse such as ket-
amine and phencyclidine. Human biological matrices are different: from the most
common plasma and urine to OFs, nails, sweat, and hair. In fact, Bush from SAMSHA
wrote in 2008 about the fundamental understanding that the window of drug detec-
tion for urine, hair, OF, and sweat patch specimens are neither equal nor identical, but
the results from each specimen can be used in a complementary manner [
129
] .
A kind of guidance has been drawn for the chemist/toxicologist who approaches
to develop a new analytical method (from sample pretreatment to chromatographic
separation and MS detection) and to validate new methods. Different strategies are
possible with MS detector, especially with high resolution instrumentation. This
chapter focuses on analysis on targeted molecules (so-called confirmatory analysis),
but there are many application of LC-MS in GUS/STA: in this case the aim is to
identify unknown compounds that may be present in a selected matrix. However, in
this case, it needs subsequent confirmatory analysis to be used in a court. The most
cited international guidelines are compared with regard to the parameters to be
monitored during method validation and how effectively to evaluate them; among
these matrix effect plays a significant role in LC-MS methods.
