Sharp Area Fluctuation with LC-MS

[wenzhe]

Dear Friends,

I am working with LC-MS (TSQ Quantum Ultra) and got big variations in response between injections. The chromatographs are always consistent, implying LC part is not the root cause. On the contrary, MS part is paining. Could anyone help me with this problem? I attached the conditions and results.

Column: YMC AQ12S05-1546WT
Mobile Phase: A: Acetonitrile with 0.1% Formic acid
B: Water with 0.1% Formic acid (pH 3)
Flow Rate: 0.6 ml/min
Gradient (A): 0 min (25%)-3 min (15%)-5 min(25%) - 10 min (25%)

Spray Voltage: 4500 V
Sheath Gas: 50 Arb
Aux Gas: 5 Arb
Ion Sweep Gas: 1 Arb
Skimmer Offset: 17 V
Capillary Temperature: 400 ºc
Collison Pressure: 1.2 mTorr
Tube Lens Offset: 100V (Compound A) / 80V (Compound B)
Collision Energy: 13V (Compound A) / 29V (Compound B)

[wenzhe]

[img]C:\Users\wenzhe\Temporary\LC-MS%20Method%20for%20Vlado2[/img]

[wenzhe]

Hope this figure works.