Peak Symmetry

[wrighty]

Morning All,

Could somebody help me out with a problem i've got regarding peak symmetry.

I am currently running a sample with contains 7peaks, 6 of these are approx 1% (each) and the seventh peak makes up over 90% of the total area.

Now, i am developing a method for this sample, resolution is good but i am struggling with the symmetry.

The EP states that peak symmetry must lie between 0.8 and 1.2. The six small peaks are around the 1 mark but the main peak is 6!. When i look at the profile of the big peak it is obvious why the symmetry is so poor ( a gradual increase and then a sudden drop).

For those users with EP knowledge, can i justify this method based on these symmetrys?

cheers

steve

[shaun78]

No. The peak exibiting the symmetry of 6 is not meeting ICH guidelines, which the EP should also be following/referencing.

What type of a column does the EP specify (packed/cap).

I know the EP allows fluctuiations on column flows/velocity. Speeding either up will help the symmtery ... however for something that far gone you may not have much success "fixing" it.

Cheers!

[chromatographer1]

Your main peak is overloading the column.

Perhaps you can do two injections, one for the 1% peaks and then a second injection with an increased split ratio or smaller injection size so the 90% peak will be able to meet symmetry requirements?

best wishes,

Rod

[wrighty]

The method itself is not EP. It is a method that has been used for many years within the company. As a result, it has landed on my lap to validate the method. If a method exists in the EP then the comapny likes to follow it. If there isnt then we create system suitability acceptance criteria we like to follow the general guidelines set out in the EP.

The split is a good idea and is worth a shot. It is something that i never thought of (i've had the Friday feeling all day so the brains been on go slow). Will give it a shot after the weekend.

cheers

steve