Chromatography Forum

Dear All
Below there are two chromatograms of DNP-formaldehyde at 5 and 100 ppm


formaldehyde-DNP 5 ppm


formaldehyde 100 ppm

As you can notice in the peak at 100 ppm there is a bump eluting straight after the peak, while in the peak at 5 ppm the baseline after the peak is fairly flat.
I would like to know whether the bump observed in the peak at 100 ppm is due to column overload or it might be some compound coeluting with formaldehyde.
The column used was a phenomenex columbus 150x4.6 mm and mobile phase a gradient 0.6% perchloric acid-methanol at a flow rate of 1.0 ml/min. DAD signal at 365 nm.

Many thanks for your help

Looks like overloading to me, maybe column and detector...

If you did a vertical scale expansion of the 5 ppm peak, I think you would find that the bump is there. From the looks of the 100 ppm peak, you are saturating the detector (going above its linear range) rather than overloading the column.

I agree, I believe if you looked, yo would find that the bump is there on the 5 ppm.

Although, your peaks look very wide