September 11, 2024, 02:10:34 AM
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### Topic: Calculating Peak Width (Liquid Chromatography)?  (Read 2631 times)

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#### yungsushi

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##### Calculating Peak Width (Liquid Chromatography)?
« on: May 05, 2024, 03:10:49 PM »
I have a homework problem asking me to calculate the peak widths of a two-component mixture on a 20-cm packed liquid chromatography column. I know the flow rate (0.30 mL/min), the dead time (5 min), and the retention times of both components (35 min and 60 min). I know that the retention time and peak width are related by the equation $$N = 16(\frac{t_{r}}{W})^2$$ where N is the number of plates a column has, tr is the retention time, and W is the peak width. I also know that $$N = \frac{L}{H}$$ where L is the packing length and H is the plate height. Since both equations equal N, I can set them equal to each other, but that leaves me with 2 unknowns: H and W. Am I missing another equation that I could use to solve for H and leave me with just W as an unknown, or is there not enough information given to me to solve this?

#### Hunter2

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##### Re: Calculating Peak Width (Liquid Chromatography)?
« Reply #1 on: May 05, 2024, 04:06:44 PM »
H is the packaging height. This information should gives your column. Probably the 20 cm.

#### MOTOBALL

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##### Re: Calculating Peak Width (Liquid Chromatography)?
« Reply #2 on: May 09, 2024, 03:48:02 PM »
As stated by the OP, H is the plate height, NOT the "packaging" height, whatever that may be.

L/H = (4 Tr/W)sqd

So, W = (4 Tr) / sq rt (L/H) ; NOTE you may need to correct Tr to Tr - T0, where T0 is the dead time, i.e. NO retention; N = usually around 5,000 - 10,000 plates, for HPLC column.

You have not been given  H = HETP = height equivalent to a theoretical plate, so cannot give a numerical answer.

Regards,

Motoball