Biomedical Engineering Reference
In-Depth Information
found to offer the best overall recovery, followed closely by a mixed-mode polymeric
sorbent. It was reported that the C
8
material offered the cleanest sample extracts.
After SPE direct injection of eluate or its dilution prior to injection into LC-MS
apparatus is possible.
Limitations of SPE include the coextraction of interfering compounds and poor
extraction of some drugs, but an important advantage is the possibility of building
automated systems and obtaining the analytical procedure online, as this is the
recent trend.
Recently Bjock et al. [
103
] have developed an analytical method for the determi-
nation of 19 drugs of abuse and metabolites in whole blood. The following com-
pounds were investigated: amphetamine, MDA, MDEA, MDMA, methamphetamine,
cocaine, BEG, morphine, 6-MAM, codeine, methadone, buprenorphine, norbu-
prenorphine, ketobemidone, tramadol,
O
-desmethyltramadol, zaleplone, zolpidem,
and zopiclone. Sample pretreatment consisted of PPT prior to automated SPE. The
samples were mixed, sonicated, and centrifuged. SPE was performed by using mixed
mode cartridge: the highest and most reproducible recoveries were obtained with the
Isolute Confirm HCX (130 mg, 3 ml) SPE column with 80:20 toluene/ethyl acetate.
An LC-MS system was used for separation of the target analytes and the total time of
analysis was 35 min to ensure reequilibration between injections. The described
method was successfully applied by the authors for screening and quantification of
the 19 targeted drugs of abuse in 412 authentic forensic cases from October 2008 to
February 2009 in DUIDs cases (Driving Under Influence of Drugs).
In the American Federal Bureau of Investigation (FBI) laboratories, Jagerdeo
et al. analyzed cocaine and four metabolites: BEG, EME, ecgonine, and CE.
Pretreatment of the samples to precipitate plasma proteins was carried out by adding
zinc sulfate to blood sample. Filtered samples were transferred and were prepared
for the online SPE system, with an anion exchange based cartridge. Detection was
performed using a Qtrap Mass Spectrometry equipped with a turbo spray ion source
operated in positive electrospray ionization mode. This method was validated and
demonstrates excellent accuracy and precision, and an excellent lower limit of
detection (also due to the high performing instrumentation) [
104
] .
Bouzas et al. [
95
] developed a quantitation method for the determination of drugs
of abuse (opiates, amphetamine and derivatives, cocaine, methadone and metabo-
lites) in serum by using online extraction coupled to LC-MS/MS. The online extrac-
tion procedure described consists of an extraction column and an analytical column,
which were coupled online. A PPT procedure was performed with zinc sulfate: an
aliquot of 0.1 M zinc sulfate in methanol was added to the serum sample in a pro-
portion of 2:1 (
v
/
v
) to serum. Analytes were extracted by a short pentafluorophenyl
silica column and separated on a longer analytical column with the same stationary
phase. Recoveries of all analytes were above 80 %. The proposed procedure by
Matuszewski et al. [
64
] was used for the evaluation of matrix effect:
ME(%) = B/A × 100, where ME is the matrix effect (suppression or enhancement)
and B corresponds to peak areas for standards spiked after extraction into sample
extracts and A to peak areas obtained in neat solution standards. Authors compared
this method to offline SPE coupled with GC-MS and results showed that LC-MS/
