Examination of Firearms Review: 2007 to 2010 - Interpol

extraction efficiency for certain drugs, and ease of automation for on-line
coupling of SPE to chromatographic systems [286,287]. Pre-treated samples
were injected into the LC system with two extraction columns. A comparison of
the LODs of LLE and SPE for alkaline drugs was conducted, and most of the
drugs had lower LODs using SPE versus LLE [288]. In addition, several
methods have been reported to use online coupling of SPE to LC-MS/MS for
the analysis of basic drugs of abuse in human serum [289], 21 therapeutic and
21 drugs of abuse in urine [290], tricyclic antidepressant drugs (amitriptyline,
desipramine, imipramine, and nortriptyline) in serum [ 291 ], 19 drugs of
different classes in equine plasma [292], and amphetamines in blood and urine
[293].
3.2.4 Microextraction in packed sorbent (MEPS)
Although SPE has many advantages over LLE, it normally has a higher cost
because the SPE cartridges are typically disposed of after each use. To
address this, the microextraction in packed sorbent (MEPS) technique was
developed, where the packed syringe can be used more than 100 times (and
also allowing the use of smaller sample sizes, as small as 10 µL) [294]. The
use of MEPS in sample preparation was reported for cotinine [295] and
metabolites of monoterpenes [296] in urine by GC-MS, cocaine and its
metabolites in urine by real-time source coupled to TOFMS [297], anti-cancer
drugs such as cyclophosphamide [298] and busulphan [299] in plasma, and
β-blockers such as acebutolol and metoprolol in plasma and urine by
LC-MS(MS) [300], anesthetic drugs in plasma [301], and fluoroquinolones in
urine by CE-MS [302]. Determination of dopamine and serotonin with MEPS
connected online to LC-MS/MS was reported to be a facile, more rapid, and
lower cost method [303].
3.2.5 Solid-phase microextraction (SPME)
SPME has several advantages such as ease of automation, good linearity, and
high sensitivity without the need of solvents. It can also be utilized for direct
measurement of biological samples such as whole blood or plasma [304]. But
longer extraction times are required for analytes with low volatility in complex
matrices, and the capacity of SPME fiber is limited [268].
Automation of SPME on a 96-multi-well plate format improves the speed and
throughput of the method to be at least comparable to automated LLE,
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