Peak tailing factor computation.

[irwine]

Hi
I am new here in this forum. It's kinda nice to have a forum like this for those people involve in chromatography. You guys rock!!!

By the way, I need some help regarding the system suitability test. We all knew that SST comprises the No. of theoretical plates, resolution, tailing factor, etc... Is there a way to compute the tailing factor without using a software? I mean, is there a way to determine the tailing factor manually? The data provided were the chromatogram itself with area, retention time, and height..

Thanks.

[Shanextan]

First, you need to understand the definition of the tailing factor. Then you may use a rule to measure the peak width.

[tom jupille]

Shanextan is correct. The definition of tailing factor long predates the use of data system software. It's actually easiest to do with a printout of the chromatogram, a sharp pencil, and a good ruler.

[irwine]

I am using the peak width at 10% method. So you mean that I have to trace the peak to a graphing paper, then get the peak width at 10% height, get the point at the rising part and the sloping part of the peak then correspond it to the y-axis (time-axis)?

Waahhh... So many computation to do..

[shaun78]

No.

USP definition for failing:

W[0.1]/2f

W[0.1] = width of peak at 10% of its height (measure the height of the peak from the baseline to apex in cm. Multiply that height by 0.1; Measure up from the baseline that result (say the height was 100 cm, I measure up from the baseline 10 cm)).

f = half width of the peak as drawn from apex down to beaseline. So, drop a line from the apex of the peak to your baseline. Measure from the beginning of the peak at the baseline to your f line in cm. This value is f. Multiply that by 2.

I hope this helps...

Shaun

[DR]

There's an old letter I submitted to LC*GC (Ouchi, Glenn, (Feb. 1993) letter to "The Data File" LCGC 11, (2) 110. A method to calculate Tailing factors using Windows 3.x software) that details how to calculate tailing using a screen shot dropped into Microsoft Paint. You need a good view of your peak of interest, then you exploit the (x,y) mouse coordinates on the status bar of MS-Paint in order to get your heights and widths.

[Shanextan]

USP defines the tailing factor at 5% the peak height.

It is tedious to calculate tailing factor manually. Most people use software now.

[shaun78]

Yes, the USP does define it at 5%. However the calculation remains the same no matter if using 5 or 10%. I changed the calculation to represent 10; if using 5% the W[0.05] = height of peak in cm * 0.05.

I completely agree, it is tedious and people do use software now. Sounds like a good excust to me to write a quick software validation protocol to confirm that the software calculates the same thing you do by hand within +/- x%.

[Uwe Neue]

It's tedious, but "the software" agrees with you. This is why tailing factors vary a lot, even if "the software" does it.

Signed: "the software"...

[irwine]

Thanks guys for the information..

By the way, where can I get a free software of the computation of tailing factor. Our software doesn't include calculation of the tailing factor. My unit is Merck Hitachi D7000.

It's pretty da** difficult to compute it manually.. hehehe:)

Thanks again guys..

Irwine

[wanda50]

I agree that you need to know the principle behind the calculation. the current generation is spoiled!!! Even 15 years ago we did all system suitability calculations by hand here.

[Jumpshooter]

I must confess that the only and last time I ever used a manual calc'n of tailing factors was in an "Instrumentation" course I took as an undergrad wayyyy wayyyy back in 1988. Thank goodness for the software!

[irwine]

Generation today are spoiled because of the technologies in computers and softwares. I was trying to compute for those SST manually in order to know the basic that lies behind the creation of the software.

But unfortunately, I don't have a software which will verify my manual calculations.

Our HPLC unit and software doesn't include calculations of the Tailing factor, which I need..