By sulfa on Tuesday, January 23, 2001 - 04:10 pm:
I need to separate 12 sulfa drugs (sulfanilamide, sulfaquinoxaline and others) at pH 3.8 and recommend me in this forum SymmetryShield, I think 5” 250 x 4.6. The questions: what back pressure can I expect? RP 18 or RP 8?
Thanks for Your help.
By Anonymous on Wednesday, January 24, 2001 - 07:00 am:
Many methods for the seperation of sulfa drugs have been developed on SymmetryShied RP8. The back pressue is dependant on: flow rate, mobile phase composition, column length/diameter/particle size, temperature, HPLC system. Why are you concerned what the expected back pressure would be?
By sulfa on Thursday, January 25, 2001 - 05:54 am:
The conditions: ACN 15%: Buffer 85%. Column temperature: 50șC. Column SymmetryShield RP 8, particle size:5”, diameter: 4.6 mm, length: 250 mm. Equipment Hewlett 1050. I need to know at what level of pressure I'll work.
By Anonymous on Thursday, January 25, 2001 - 07:32 am:
Most modern HPLC systems can deal with backpressure of at least 4000 psi. So again, I ask the question, why do you care. But as a guess, with your fairly large particles, large diameter column, fairly high temp, and a flow rate of 1 mL/min....between 1000 and 1500 psi, maybe even less.
By Uwe Neue on Thursday, January 25, 2001 - 04:28 pm:
I expect the backpressure to be around 1500 PSI. Both the RP8 and the RP 18 work equally well. You seem to have an applications example in your fingers. I would start with the column recommended there. Alternatively, I can check for some background information.
By sulfa on Friday, January 26, 2001 - 06:54 am:
My fittings are PTFE and I try to work down of 3000 PSI, and the equipment suffer most less the use at low back pressure.
By sulfa on Friday, January 26, 2001 - 07:11 am:
Uwe Neue: I have one aplication, but my sample is most complicated than that. I'll apreciate all aditional information.
Thanks
By Uwe Neue on Monday, January 29, 2001 - 03:43 pm:
We ran a set of sulfa drugs with a 3.5 micron Symmetry C18 4.6 mm x 100 mm column at 1.5 mL/min with water:methanol:glacial acetic 79:20:1. Samples: sulfanilamide, sulfadiazine, sulfathiazole, sulfamerazine, sulfamethazine, succinylsulfathiazol. On SymmetryShield, I would expect about the same mobile phase conditions.
BTW, we ran this separation to 10,000 injections without change in column performance. Of course, this takes a while ...
By sulfa on Wednesday, January 31, 2001 - 06:00 am:
Thanks Uwe Neue. 10,000 inyections is a lot of time and with manual inyection a good muscle practice too.
Thanks again
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