Chromatography Forum

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

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?

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.