Biomedical Engineering Reference
In-Depth Information
6
4
2
0
0
20
40
60
80
Sample Sequence No.
Neat Solution
CS and QC
Incurred Sample
Fig. 10
Gradual decrease of internal standard response caused by the charging of the mass spec-
trometer. Analyte: escitalopram. Reproduced from ref. [
36
] with permission from Elsevier
20
0
ANA
IS
ANB
ANA/IS
ANB/IS
-20
-40
0
5
10
15
20
25
30
Injection Sequence
Fig. 11
An ascorbic acid-contaminated triple quadrupole mass spectrometer affected the responses
of levothyroxine (ANA), liothyronine (ANB), and
13
C
6
-thyroxine (IS) differently when a neat solu-
tion sample was repeatedly injected, resulting in a gradual increase of analyte/IS response ratios
for one analyte (ANA) while gradual decrease for the other (ANB)
Therefore, it is expected that there might be differences in matrix components for
different samples because each sample is from an individual subject and collected
at different sampling time. These differences could cause many different types of IS
response variations.
