Malic acid and l-carnitine

[qfiviera]

Hi guys.
I have Malic acid and L-Carnitine in a sample. Malic acid shows two peaks when injected alone, one sharp at about 2 min and the other one at 3.7 min. I´m pretty sure the second one is Fumaric acid, when injected a solution of fumaric, same retention time 3.7 and spectra, don´t know if it is degraded by sovents or system, or if it is in the material. In presence of L-carnitine, the second peak in Malic acid splits into two separated 3.3 and 3.7 min, 1
5 - 2.0 resolution peaks. When I inject a solution of fumaric and L-carnitine, shows the same splitted peak at 3.3 and 3.7 min. Is it possible for L-carnitine to affect chromatography somehow, interacting?
System:
C18, 250 x 4.6 mm, 5 um
MP: Heptansulphonate (1132 mg): 11.5 mL H3PO4 to 2000 mL with water : MeOH 40.6 mL

[HPLCaddict]

What are the retention factors of all those peaks? The retention times seem pretty low for such a big column. At which flow-rate are you running?
What is the sample solvent? Are you probably seeing split peaks because of some solvent/mobile phase mismatch?

[Peggsy]

I'm led to believe that malic acid is synthesised from fumaric acid. Molar absorptivity of fumaric acid is some 100 times greater than that for malic. So even for a 99% pure malic acid stock, there would be detectable amounts of fumaric acid.