I want to asay ketoconazole in tablets after extraction with an acidic solution. I have found in the literature the following method: " the drug was extracted with aq. 5% citric acid and the mixture was filtered before analysis. A portion of the solution was analysed by HPLC on a Radial-PAK column (10cm x 8mm)of C18 micro BondapaK (10micra) with a mobile phase (2mlmin-1) of methanol-water-acetic acid (135:64:1) and detection at 242nm."
Unfortunately I don't have C18 columns with these lenght and internal diameter, only columns with 3,9 to 4,6mm internal diameter, 7,5 to 30cm long.How can I adjust the chromatographic conditions to make the method work with a 4,0mm I.D. column without using the trial and error approach?
Thanks in advance for your help!

Dear Maria:

RadialPak is a brand name of Waters Corp. This particular type of column has a flexible, polypropylene body. It needs a special column holder which compresses the column radially - hence the name.

An 8mm ID by 10 cm Radial Pak is about the same as using 4.6 mm ID steel column. So you can happily use your 3.9 mm or 4.6 mm C18 column with more or less the same HPLC conditions. You may just have to change the flow rates a wee bit here and there.

Otherwise other conditions remain unchanged.

Do let me know if you need more help.

regards.

s.k. srinivas
stimulus, india.