Chromatography Forum

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.

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

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.

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..

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

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.

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

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

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%.

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"...

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

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.

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!

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..