Chromatography Forum

Hi!
I'm having problems with linearity for my calibration curve of pyridxoine. I only get an R^2 value of 0.934 and the curve looks really bad. I am using ESI and single quadropole MS. The column is sunniest rp-aqua (2.0 i.d. x 150 mm) and I use a gradient of ACN and buffer (20 mM ammonium formate/ 0.05% formic acid). Starting with 100% buffer to 70% buffer for 15 minutes. I'm running SIM mode for m/z 170. I am also analyzing ascorbic acid and biotin with this method and they both show great linearity.

Any ideas or tips for improving linearity?

You should describe in more detail HOW the curve for vitamin B6 looks bad, or better yet, post a picture of the curve.

The compound has a phophate group on it, which can be problematic.

Agilent has a medronic acid solution out that has helped me for improving peak shapes and linearity of chelating compounds. Give that a try maybe?

Anal. Chem. 2018, 90, 15, 9457–9464