502 / 658
Conclusions
Positive and negative ion detection of co-eluting drugs
was accomplished in a single chromatographic run
using automated polarity switching. Drugs that
underwent a neutral water loss were further fragmented
using WideBand Activation to provide a diagnostically
rich MS/MS spectrum for structural confirmation.
The compound ketoprofen underwent a prominent,
non-specific neutral loss of formic acid and was further
analyzed using an MS
3
transition. Full-scan MS
n
data
was reprocessed to quantify all 16 compounds by
reconstructed ion chromatograms (RICs), or post-
acquisition MRM, and provided results comparable to
triple quadrupole SRM quantitation. It is possible to
achieve the low % RSD required in quantitation due to
the fast cycle time of the Thermo Scientific LTQ. In the
case of non-specific neutral molecule losses, MS
3
experiments generated diagnostic spectra for
confirmational purposes while providing quantitative
results comparable to the MS/MS data. Results of the
ruggedness study demonstrate no appreciable loss of
sensitivity or reproducibility across 100 replicate urine
injections. Thus, using the Thermo Scientific LTQ
two-dimensional linear ion trap, we have demonstrated
the development of a simple, rapid, and rugged method
capable of confirmational screening and simultaneous
quantitation of drugs in horse urine using both full-scan
LC/MS/MS and MS
3
spectra.
0
100000
200000
300000
400000
500000
600000
700000
800000
900000
1000000
0
20
40
60
80
100
Injection Number
Area
Average Area =482146
CV =3.81%
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
100000
0
20
40
60
80
100
Injection Number
Area
Average Area =65211
CV =2.41%
0
5000
10000
15000
20000
25000
30000
35000
40000
0
20
40
60
80
100
Injection Number
Area
Average Area =18574
CV =3.43%
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
0
20
40
60
80
100
Injection Number
Area
Average Area =27690
CV =2.32%
A
B
C
D
Figure 8: Ruggedness and reproducibility for 100 consecutive injections of a 166 pg/µL standard of theobromine, caffeine, pentoxyphylline,
and ketoprofen in urine
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