Biomedical Engineering Reference
In-Depth Information
norketamine, cocaine, and BEG in hair [
158
]. A washed hair specimen (0.2 mg) was
precisely weighed in a polypropylene tube. A stainless steel bullet, 4 ml of 10 ng/ml
methamphetamine-d5 (IS) and 50 ml of 0.1 M ammonium formate buffer (pH 3.5)
were added. The tube was capped and shaken vertically for 5 min at 1,500 strokes per
min with an automatic pulverizer. After a brief centrifugation, the bullet was removed
with tweezers. The suspension was filtered using a centrifugal filter unit with a
0.45 mm polyvinylidene fluoride (PVDF) microporous membrane. The filtrate was
transferred to a conical insert with polymer feet in a glass vial to be analyzed by
LC-ESI-MS/MS.
A C18 column was used for separation at 40 °C. The mobile phase, delivered at a
flow rate of 0.3 ml/min, was 5 mM ammonium formate (pH 3.5) in water-acetonitrile;
proportion of acetonitrile was changed over a gradient. Full scan analysis with the
Orbitrap analyzer was performed with a mass range of
m
/
z
130-430 and resolving
power of 30,000 in a profile mode. Method performances were investigated,
specially accuracy was evaluated by analyzing standard reference material: the
results obtained were in general agreement with the approved values. Sample pretreat-
ment, consisting in 5 min extraction of a very small amount of hair, only 0.2 mg,
validated with reference material, represented certainly a convenient approach.
10.4.3
Cleanup
In some cases the extract of hair is directly analyzed or after a solvent exchange, or
after evaporation of the extracting phase [
134-
136,
139-
141,
147
] . Through direct
injection strong signal suppression is recorded and an extract cleanup step prior
to instrumental analysis is suggested [
141
]. The extract purification is important for
increasing the selectivity and accuracy of the analysis by eliminating potential inter-
ference and restricting the matrix effects; it is important to make the sample compat-
ible with the instrumental analysis as in this step may be a change of solvent or the
concentration of analytes so as to fall within the detection limits of the instrument.
Furthermore, the sample purification is important for safeguarding the instru-
mentation, as the sample cleanup also removes all those substances that could dam-
age it over time.
The procedures to purify the extracts appear to be mainly LLE (liquid-liquid
extraction) and SPE (solid phase extraction).
An interesting application has been proposed by Bucelli et al. [
133
] : a LC-ESI-MS
method for the analysis of 16 drugs (EME, cocaine, benzoylecgonine, morphine,
6-MAM, codeine, amphetamine, methamphetamine, MDA, MDEA, MDMA,
MBDB, ephedrine, phentermine, phendimetrazine, buprenorphine) in human hair.
The ion trap spectrometer afforded to work over the entire mass range in full scan
mode, in MS/MS and MS
n
mode. The mixture was incubated at 45 °C for 18 h and
then centrifuged. Extraction was carried out with Bond Elut Certify cartridges.
Analytes were eluted with a mixture of dichloromethane-isopropanol-ammonia.
The eluent was removed under a gentle nitrogen stream at 45 °C. For chromato-
graphic separation a C18 column was used and the elution solvents were ultrapure
