Biosample Assay by LC-MS (2)

(1) Capillary Voltage: -3.0 kv.
(2) Cone Voltage: -40 v.
(3) Collision Energy: 18 ev.
(4) MRM: m/z 299.5 →m/z 255.2.

Biosample Assay by LC-MS (1)

Happy Spring Festivals 2009!

Ionization Suppression Summary

(1) Compounds That Cause Sensitivity Suppression.
-Salts can interfere with ionization and can cluster to complicate spectrum (but also aid in identification).
-Strong bases or quaternary amines can interfere with positive mode analytes, e.g. Triethylamine(TFA).
-Acid -Sulfuric/Sulfonicacids and TFA interfere in negative mode.
-Phosphate buffer and non-volatile ion pairing agents (e.g. SDS) can cause severe suppression and complex spectrum.

(2) Dimerization([2M+H]+) can occur at high concentration, leading to non-linearity during quantitation.
-DimerSignal at m/z = (MW*2) + 1.
-Can cause non-linearity at high concentrations.

Five Ways to Reduce Acetonitrile Consumption

The current global shortage of Acetonitrile has pushed us to find 5 ways to reduce thedependence on Acetonitrile

Option 1: Reduce column ID:

Reducing the HPLC column ID from 4.6 mm to 3.0 mm can result in > 50 % reduction in mobile phase consumption.

Option 2: Reduce particle size and column dimensions:

* Reduces solvent consumption
* Maintains resolution
* Reduces run time

Option 3: Reduce column length:

Option 4: Substitute Acetonitrile with Methanol:

http://www.phenomenex.com/images/methanal_replacement.gif

Option 5: Solvent recycling (Isocratic separations only)

Reference by Phenomenex.

VIP reference for the Method Transfer....

It's time to clean the Inlet....

Agilent 6890N ECD.
Temp Ramp: 80℃（1min)----20℃/min--- 260℃（15min)----5℃/min---300℃（3min),
Detector Temp: 300℃
Inlet: 250℃
GC Column:HP-5.

Baseline drift?

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.

Agilent MassHunter could meet your request.

Go to MassHunter, File->TIC->.....

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.