LC-MS help with acrylic / maleic method

[Eric_L]

Hello, I’m new to the forums and a novice when it comes to LC-MS.

I’m trying to develop a LC-MS method to measure the residuals monomers in an acrylic / maleic acid copolymer. I’m currently running standards that are just acrylic and maleic acid in the mobile phase right now. I don’t get great separation between the two analytes but good enough to integrate through UV-Vis. The problem is that the signal for the SIM ions spreads out and doesn’t give consistent results through the mass spec. It looks like the molecules may be getting hung up in the spray chamber because the signal gets so spread out. Any help would be appreciated. Thank you.



Conditions:
Mobile phase:
90% 0.1% Formic Acid buffer
10% Acetonitrile

Flow Rate: 0.5ml/min
Column Temp: 25C
UV Wavelength: 205nm

MS Conditions:
Agilent single quad
Mode: Multimode-ES
Polarity: Negative
SIM Ions:
Maleic Acid – 115.00 | Fragmentor: 45
Acrylic Acid – 71.00 | Fragmentor: 90

Gas temp: 300C
Vaporizer: 200C
Drying Gas: 12.0 l/min
Neb Pressure: 35psig

Column: C18 Poroshell 4.6 X 50mm 2.7micron

(The reason I’m trying to develop a method through the mass spec as oppose to the UV-Vis detector is because of a problem with a loss of signal do to matrix effects in the sample. I lose somewhere between 50-60% of a maleic acid spike of 0.2-0.4% when I analyze through UV-Vis)

[LiVD]

2000 and 600 counts seems to me to be rather low, did you optimize the ionization? Getting rid of the formic acid in your mobile phase might improve this, although it will likely destroy your retention time. Have you thought about using HILIC?