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The optimization of selective reaction monitoring (SRM)
parameters was performed by direct infusion of standards.
Collision-induced dissociation (CID) data were recorded
for each analyte including optimum collision energies
for the selected ion transitions.
Table 1 summarizes all the mass transitions found for
each analyte and its relative collision energy (CE) and
tube lens values.
Results and Discussion
To ensure thorough validation of the method, neat
standard solutions, standard addition on purified
extracts, and spiked blank tissue extracts were prepared
and compared.
Table 2 lists the correlation coefficients (r
2
) indicating the
linearity of the calibration curves for the three types of
samples analyzed; five concentrations of the sample solution
are considered (2, 5, 10, 20, and 50 μg/kg or similar).
To assess the inter-day repeatability of the method, ten
replicates of spiked samples were analyzed between
days. Solutions were prepared containing all the toxins
in the five different concentrations used to perform the
calibration curves (2, 5, 10, 20, and 50 μg/kg or similar).
The repeatability of the method expressed as the
coefficient of variation percentage (CV %) has been
rated less than 20% as shown in Table 3.
Analyte
ESI Mode
Parent Mass
Product Mass
Collision Energy
Tube Lens
AZA-1
ESI+
842.3
806.1
51
207
824.2
42
207
AZA-2
ESI+
856.3
838.1
42
214
820.2
49
214
AZA-3
ESI+
828.3
792.2
48
192
810.0
40
192
PTX-2
ESI+
876.3
841.3
35
205
823.0
40
205
805.3
41
205
DTX-1
ESI-
817.0
255.0
69
197
113.1
67
197
DTX-2
ESI-
803.15
255.3
61
207
113.1
50
207
YTX
ESI-
1141.5
1061.7
50
240
570.2
467.3
40
240
OA
ESI-
803.3
254.9
68
216
113.1
50
216
Table 1: Selected ion transitions (
m/z
) of the studied compounds and optimized collision energy and tube lens value for the TSQ Quantum Ultra triple quadrupole
mass spectrometer
Analyte
Neat Solution
Spiked Purified Extract
Spiked Extract
AZA-1
0.9932
0.9965
0.9970
AZA-2
0.9973
0.9964
0.9901
AZA-3
0.9972
0.9958
0.9993
DTX-1
0.9964
0.9995
0.9953
DTX-2
0.9973
0.9966
0.9965
YTX
0.9999
0.9923
0.9988
PTX-2
1.0000
0.9977
0.9927
OA
0.9955
0.9924
0.9927
Table 2: Correlation Coefficient (r
2
) of the calibration curves for the three types of samples analyzed in
the concentration range of 2–50 μg/kg)
Analyte
Standard Deviation
Repeatability
CV%
AZA-1
0.25
0.79
20
AZA-2
0.29
0.90
18
AZA-3
0.43
1.37
17
DTX-1
0.18
0.55
2
DTX-2
0.22
0.68
9
YTX
0.12
0.40
12
PTX-2
0.39
1.36
20
OA
0.16
0.48
4
Table 3: Values of CV% obtained for the repeatability of the lower concentrated curve point (2 µg/kg)