Saturday, December 27, 2008
Monday, December 22, 2008
Maybe the collision energy (CE) is too LOW
(1) Maybe the collision energy is too LOW. The First MS is not full a fragment.(2) Are you using ESI mode?
(3) If the Molecular weight is 237, for SIM -> Here are three characteristic ions (m/z) 164,149,122 I highly recommend them.
(4) MS-MS (MRM): Need to search online for the product ion and parent ions.
(5) If only need the full scan, why not adjust the concentration of analyte.
Hope it helps.
Tuesday, December 16, 2008
Sunday, December 14, 2008
m/z (563.10761) is NOT the Molecular Ion? (II)

(1) Try to adjust the the capillary voltage: increase it a little bit each time.
If the the mass response of [M+H2O -H]- is decrease, the mass response of [M-H]- increase: then the m/z (563.10761) definitely is the molecular Ion.
If No such change happened, then the m/z (563.10761) definitely is NOT the Molecular Ion.
(2) From my view, the possibility of [M+H2O-H]( belongs to Molecular ion) is very low. Under ESI (-) negative mode, the trend of forming
the [M+HCOOmore high.
Doubt the H2O have that much acidity for forming the ion peak.
Monday, December 1, 2008
Where M/Z 425 from? ( II )
Where M/Z 425 from? ( I )
The molecular weight of your analyte is 548: 1st Mass is 549, 2nd Mass is 489, 3rd Mass are 471, 425.Here is HUGE challenge for the structural elucidation of your analyte.
From M/Z (471) to M/Z (425) , maybe belong the loss of Acetoxyl M/Z.
But it is NOT right because there are two Acyloxy in your analyte.
Will Update you by Monday Night.
Monday, November 17, 2008
Come on, Man: Don't be silly to send us this Newbie question? Are you want to test our GC knowledge?(1) Condition the GC Column according the manufacturer' recommend.
(2) Check the septum and the inlet, make sure NO cross-contamination -> inject the Blank.
(3) Optimize your method, change the Oven temp Ramp -> Higher the Initial temp, Low down the Temp Ramp.
(4) Low down the Split Ratio.
(5) Adjust the GC gas Flow Rate.
Sample Overload on Column? Example 2
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