By Anonymous on Friday, September 5, 2003 - 03:17 am:
Dear all,
I have a problem when I want to separate seven substances in our products. It consists of very different properties and concentrations. Their polarities are ranged from very nonpolar (coenzyme Q10) to very polar (Vit C). Based on the concentration in the tablet, I divided the active substances into two groups, ie above 1 mg and below 1 mg. The high concentration group contains three nonpolar substance and vit C, and the other group contains 3 polar compounds.
I try to focus at high concentration group. First, I dissolve the nonpolar compounds in chloroform, and then I mix with MeOH and water to form clear solution. By using gradient elution of THF-MeOH-0.1% trifluoroacetic acid, I can separate each nonpolar compound and solvent (chloroform) peaks. But with this condition, I cannot determine vit C that is not retained at all.
Please give me advise…
Best regards
By Anonymous on Friday, September 5, 2003 - 06:16 am:
multidimensional LC might be a possibility but two methods, two columns look like a solution to me. Not everything is a nail. Sometimes a screwdriver AND a hammer is required.
By A.Nonymous on Friday, September 5, 2003 - 07:40 am:
Try the Atlantis dC18 column, look in the brochure, there is a method described for Ascorbic acid, with 0.1% trifluoric acid.
Another column especialy designed for polar compounds (like atlantis, prevail, ...) is also possible.
By Anonymous on Thursday, September 18, 2003 - 10:18 am:
I recommend prevail C18 from Alltech. I've used this column for a wide range of applications, all AQ to all organic and back, and it works great. We are running water and fat soluble vitamins. Should be really good for the vitamin C. Sample-mobile phase solubility may be a problem and require two steps but hopefully one column.
By Anonymous on Saturday, September 20, 2003 - 10:08 pm:
Try Primesep columns from Allsep Technologies (www.primesep.com) they have reverse phase columns with embedded ion-pairing reagents. You can use isocratic or gradient method with ACN-water and TFA or other acid in the mobile phase.Columns are also working with ammonium acetate or ammonium formate. I was able to separate a very complex mixture of acids, bases and neutral compounds (peptide coupling with toluene as a marker.