Tailing and Symmetry

[fdamico]

Hello!!
A question:

What is the basic difference between symmetry Factor and Tailing Factor ?


ps I work with EP!

Thanks

[Johnny Rod]

They are two names for the same thing, tailing factor is a USP term so you are interested in Peak Symmetry for EP. I think they are both calculated using peak front and back widths at 5% of peak height, your chromatography software should do it for you anyway.

[fdamico]

Unfortunately software (HPLC Agilent, Chemstation) calculates both...
and the values ​​are different

[carls]

Chemstation calculates symmetry values using a proprietary formula unlike any other equation I have seen for asymmetry (asymmetry values are more commonly reported) . I could not find a reference for their symmetry calculation and it is not mathematically correlated with any asymmetry calculation I am aware of.

The USP tailing factor is widely accepted and differs from other asymmetry calculations in that it uses the peak width at 5% of peak height divided by 2x the front width at 5%.

Asymmetry is commonly calculated as the ratio of back to front width at a specified % of peak height, normally at 10%.

If anyone is aware of a reference discussing the chemstation symmetry calculation I would appreciate your forwarding it.

[tom jupille]

They are similar in concept but different in detail.

The Tailing Factor is defined by the USP as the distance from the front edge of the peak to the back edge, divided by the distance from the front edge to the centerline, with all distances measured at 5% of the maximum peak height.

The Asymmetry Factor is defined by ASTM as the distance from the centerline to the back edge divided by the distance from the centerline to the front edge, with all distances measured at 10% of the maximum peak height.

Here's a diagram taken from our Fundamentals of HPLC course:


Because the measurements are made at different levels on the peak, the two parameters cannot be exactly converted. They are generally similar in magnitude with the Asymmetry Factor usually being a bit larger.

[Johnny Rod]

The diagram above shows also the calculation of EP symmetry factor if done at 5% height (width divided by twice peak front width). Chemstation seems to use area:
http://www.chem.agilent.com/en-US/Suppo ... 04398.aspx

[zheyin]

Hello!!
A question:

What is the basic difference between symmetry Factor and Tailing Factor ?


ps I work with EP!

Thanks

Can you tell me where can you see the Tailing factor in Chemstation?
Which report type and how did u choose it to show?
thank you!

[fdamico]

Can you tell me where can you see the Tailing factor in Chemstation?
Which report type and how did u choose it to show?
thank you!

Hi.. The report is Extended performance...
Line: USP Taling

[zheyin]

Can you tell me where can you see the Tailing factor in Chemstation?
Which report type and how did u choose it to show?
thank you!

Hi.. The report is Extended performance...
Line: USP Taling

Seems to me the method must have calibration method in it.
i.e. the method must give I.D. for the peak of interest.
Otherwise, the extended report does not have info for the peak of interest.
I hate ChemStation
Miss Empower

[mostafa.mo2]

Can you tell me where can you see the Tailing factor in Chemstation?
Which report type and how did u choose it to show?
thank you!

Hi.. The report is Extended performance...
Line: USP Taling

The report is Extended performance don't give USP tailing factor
please tell me how you get it