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working standards (WS1 to WS3) followed by a reagent blank, control sample, and
samples.
d.
Re-inject working standards approximately every 4 hr. (e.g., enough t ime for 16
samples with analysis cycle time of 15 min). Correlation coefficient of each set of
calibration curves should have r
2
>0.9990 and calibration curve residuals should be ≤4%.
Samples should be bracketed by two sets of such valid calibration curves.
Table 4. Mass analysis parameters
Retention time
typical, min
Molecular
ion
(precursor)
Product ion Dwells
Cone
voltage
Collision
energy
Choline
2.5
104.2
60.3
0.025
40
12
Choline-d
9
2.5
113.4
69.3
0.025
40
15
Carnitine
4.4
162
103
0.025
32
15
Carnitine-d
3
4.4
165
103
0.025
30
15
Table 5. Mass Spectrometer (Xevo TQ-S) operating conditions
Ionization Mode:
ESI positive
Capillary voltage:
3.6 KV
Collision Gas Pressure
3 to 4 e
-3
Source Temperature:
150ºC
Desolvation Temperature: 350ºC
Cone Gas Flow
50 L/hr.
Desolvation Flow Rate
1100 L/hr.
PWHH
0.7 AMU*
Instrumental resolution parameters for the TQ-S are setup by IntelliStart to
achieve a resolution of approximately 0.7 amu across the mass range
Table 6. Chromatographic Parameters
Mobile Phase A
10 mM ammonium acetate (95/5 water/ acetonitrile v/v)
Mobile Phase B
10 mM ammonium acetate (5/95 water/ acetonitrile v/v)
Flow Rate
0.7 mL/min (analytical)
Flow Rate into MS
Full flow
Column
ACQUITY UPLC BEH HILIC 1.7
m, 2.1×100 mm
Column Temperature 25 °C
Injection Volume
10 µL
Injection Type
Full Loop
Sample temperature 8 °C
Candidates for 2016 Method of the Year
329