Chromatography Forum

Hello,
I am analyzing two surfactants (both acids) using HPLC on a Poroshell 3x50 mm 2.7um column and am finding that there is consistently double-peaking at two retention times for the 13-C internal standard for one of the compound (0.4 minutes apart). The compound itself it usually ok, but does sometimes have a smaller double peak. When I analyze the standards on a larger 4.1x150 mm, 5um column, I do not see the split peaks. Any help is greatly appreciated!!
Image here: http://imgur.com/yEoFCOc
Method Flow rate: 0.8 mL/min
Injection Volume: 2 uL
Gradient: A2= 2 mM AmAc in water; B2= 2 mM AmAc in methanol
0 to 0.25 min 40% B2
0.25 to 2.50 40 to 100% B2
2.50 to 7.00 100% B2
7.00 to 10 min 100 to 40% B2

Hello

Please paste chromatograms and write method parameters.
Otherwise it will take ages to guess what kind of problem you have.

Regards

Tomasz Kubowicz

What is the pKa of your analyte? Maybe the two peaks are charged and non-charged species of the same compound. Try to run this method with 0.2 % formic acid instead of AmAc and see what happens. And reduce dwell time for your copmounds, you only have 5 points per peak, this is not enough for reliable integration.

Edit: I just saw your daughter ion is 80 m/z: Is your compound a sulfonic acid? If yes, formic acid will be too weak. Better try a mixed mode column, see sielc.com if you find similar compounds in the applications list.