Question about scaling up methods

[Mike H.]

I have a method that uses a SB-aq 50mm x 4.6mm x 1.8µm column. There is an impurty that needs to be concentrated in order to do MS. I plan to use a similar C-18 column, 9.4mm x 250mm 5µm.

I planned to just use a scale up calculator to connvert the mathod to the new column, but after entering the parameters, the converted flow for the larger column is less than the optimal flow suggested by Agilent. 5ml/min-10ml/min. but the method calculator says to use 2.55ml/mim.

Is there a way to convert to larger column, use the recomended flow and still preserve the elution order?

[tom jupille]

What flow are you using on the small column?

[Mike H.]

What flow are you using on the small column?

50mm Zorbax C-18 aq 4.6 mm id, 1.8µm, flow 1.7ml/min. I'm trying to scale up and preserve selectivity to a Zorbax C-18 prep column, 250mm, 9.4mm id, 5µm.

I used one of the numerous scale up calculators on the net, but the scale up parameters generated state a flow of 2.55ml/min which is below the optimal flow of the prep column 5-10 ml/min. I don't know if this is because this method cannot be scaled up in a manner that preserves everything or if it's some error in the calculator.

[AA]

When I did the calculation for flow rate, I got 7 mL/min

Flow Prep= Flow Analytical X (Diameter Prep)Squared/(Diameter Analytical)Squared

Flow Prep = 1.7 X (88.36/21.16)

Flow Prep = 7.1 mL/min

Also, you dont need a 250 mm column for this, a 150 mm column 5um (packed with the same chemistry of course) should give you similar separation.

You can estimate the length needed for the prep column using this calculation Length/Particle size

50 mm/1.7um = 29.41

150 mm/5um= 30.00

A 250 mm column can certainly work, but wouldnt really be needed. Last thing, dont forget to scale the injection volume if you want similar chromatography.

[HPLCaddict]

The scale-up calculator used for the calculation obviously scaled not only to the column diameter, but also to the particle size:
7.1mL/min * 1.8µm / 5µm = 2.55 mL/min

I'd go with what AA said. Use 7 mL/min on that big monster, possibly using only 150mm length, if available.

[Mike H.]

This was helpful. Thanks