Waters Oasis On-Line Columns SPE Columns For LC/MS/MS - Manual (Page 3)

Oasis On-Line Columns SPE Columns for LC/MS/MS 3
[ Care and Use ManUal ]
IV. typICal ChromatographIC CondItIons
A very fast gradient is run with a total run time, including
re-equilibration, of 3.0 minutes. The gradient profile is shown below
(Table 1) where mobile phase B is 100 % aqueous with 0.5 % formic
acid and mobile phase A is 100 % acetonitrile with 0.5 % formic
acid. These mobile phases are recommended for the analysis of
basic drugs. For acidic drugs, ammonium hydroxide is used instead.
The switching valve diverts the cartridge effluent to waste for the
first minute to prevent proteins and other endogenous interferences
from entering the ESI interface. The valve is switched after one
minute to redirect the flow to the MS. The gradient is carried out at a
0.4 mL/min flow rate. The injection volume of diluted plasma can be
as low as 10 μL up to 200 μL depending on the required sensitivity.
The expected lifetime is 200 injections with a 200 μL injection
volume.
Table 1: Oasis HLB Gradient Method
A: Acetonitrile + 0.5% formic acid or 0.5% NH
4
OH
B: Water + 0.5% formic acid or 0.5% NH
4
OH
Figure 1: 10 Port Valve Setup for On-line SPE-LC/MS/MS
Time (min) HPLC Gradient Flow
0.4 mL/min
Valve Position
A B Function
0.0 5 95 Load Position
0.5 5 95
1.0 95 5
2.6 95 5 Elution Position
2.9 95 5
3.0 5 95 Equilbration/Load
MASS
SPECTROMETER
WASTE
ALLIANCE HT
515
System
10
9
8
7
6
5
4
3
2
1
Elution
Position
MASS
SPECTROMETER
WASTE
ALLIANCE HT
Oasis
On-Line
Column
Oasis
On-Line
Column
515
System
10
9
8
7
6
5
4
3
2
1
Load
Position