My peaks have a slight peak tailing so half height or half width is appropriate but do I use
R = (RT1 - RT2) / [0.5 * (W1 + W2)],
http://sciencing.com/calculate-hplc-resolutions-7547102.html
OR
Half-width method (Resolution used in Performance Report):
page 249 of the report. That method used for agilent 1200 chemstation calculation of resolution so do I use this or the above. I do not know much about HPLC statistics or QC so make the answer simple for me to understand please.
Both equations are one and the same thing, the first one uses base width, the other one uses width at half height. How much tailing do you have? If it is excessive, then resolution values may not be correct, otherwise most people use the half width, with the knowledge that peaks have little bit tailing. Unfortunately, no simple method is available for calculating resolution in Agilent's software other than the methods of "moments". The methods of moments is far too complicated for everyday use. Keep in mind that Agilent's symmetry in the reports has nothing to do with the USP tailing factor.
Use the equation given to you by your chemstation software. These equations have already been validated by Agilent in accordance per 21 CFR part 11.
Yes, I think the validated equation is more often used rather than a statistical empirical made method. The validated equation is more modern industry so that is good advice. I have slight peak tailing. I will check out that article Farooq on peak quantification and methods that you published. Visual examination may not suffice. Automated is best.
Dear Mel, The Excel sheet in our total peak analysis can estimate the tailing factor for you. That work is more useful for people engaged in column packing or those who are interested in unusual peak shapes seen e.g. chiral chromatography. If you have large number of peaks, Excel sheet can become tedious. Agilent's ChemStation can calculate USP tailing for you as well, if you go to "Extended Report".
The statistical methods of moments is not empirical, it is the most accurate way of calculating peak parameters. Nobody uses them in general because of low precision and the column efficiency looks bad if you calculate it with the second moment.
it is simple using vernier calipers.
First convert the units of time in mm(millimeters) . take the print of chromatogram and measure the width from 1-5 minutes.
for example : if the widht of 5 minutes is 250 mm, each minute is 50 mm .
If T1 is 7 min and T2 is 10 minutes. after coversion, T1 is 350 mm, T2 is 500.
Measure w1 and w2 of the two peaks in mm
Now apply the values of T1 and T2 and w1 and w2 in the equation. the resolution will come in number.
Regards,
Bujji Reddy Kanchi.
My printer does not work in the laboratory. Converting min to mm does provide a number only
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