Help the novice :)

[tounsi]

HI everybody, I want to study the stability of the levomepromazine and I chose the following chromatographic conditions:
- Column C8
- mobile Phase: mixture (KH2PO4 pH 3,5 - Acétonitrile) (30:70
- detection 250 nm
- Sample of levomepromazine reference : 50 mg in 50 mg of mobile phase
During the separation I had this chromatogramme. How you can interpret these abnormalities
THANK YOU

http://img80.imageshack.us/img80/520/ssl23917.jpg

Edit 4/8/09: I substituted a smaller version of the graphic for faster loading.
-- Admin

[skunked_once]

First guess in the column problem sweepstakes: There could be a void at the head of your column causing the column fronting. Is this a brand new column? Do you get the same shaped peaks if you run a test compound?

[tom jupille]

First guess in the column problem sweepstakes: There could be a void at the head of your column causing the column fronting.

And the second guess would be partially-plugged inlet frit. Either way, the tipoff is the fact that all of your peaks show the same problem. That suggests that the problem occurred when the peaks were still together (i.e. at the head of the column or upstream from that.

[AA]

If you have really dissolved 50 mg of sample in 50 mg of mobile phase, you are likely overloading this column. Make a more dilute sample and see if the peak shape improves.

[tom jupille]

I took the liberty of substituting a smaller version of the graphic in the original post to speed up loading.