Chromatography Forum

Hi ,

I am extracting monensin from soil and water samples and these samples contain surfactant Brij 35 and it caused some troubles with LC-MS so I am thinking to remove the surfactant from the extract before analysis.

Could you please guide me to a method which can remove the surfactant?

Looking forward to hear from you

Thank you very much in advance

Emi

Waters sells an acid-labile surfactant that might be useful for this. It's normal application area is something completely different.

Thank you very much Uwe for your reply but I still don't understand your point clearly.In addition, I already have the surfactant in the extract and I wonder if there is any step to remove the surfactant before anaylsis .

Thanks again

Emi

I do not have an idea how to solve the problem with the samples that you have. This was an idea for avoiding the problem with future samples.

Your surfactant is non-ionic and you target compound is ionic and acidic in nature(pKa around 3?). You can use mixed-mode anion-exchange column and guard with low organic, trap surfactant on the guard column and analyze you molecule by ELSD/LC/MS or low UV (205 nm). The guard is being washed in opposite directin during you run (switching valve required)

Please provide me with your email and I will send you few files for review

Thank you very much Uwe ,I got your point and it sounds good for the future as you said.

Thank you very much Vlad for your advice ,I do want to read more about these solutions and looking forward to recieve the files and my email is emisamir55@yahoo.ca.

I found this application was quite interesting. Here is my two cents:

Brij 35 is a mixture of nonionic ethoxylates with different alkyl chain length (hydrophobe) and for each alkyl chain length different number of EO numbers can be attached to it. Therefore, tens of peaks show up on a RP column in a wide time frame, and they interfere with the analysis of the acidic drug in your case. One possible solution is to use Acclaim Mixed-Mode HILIC-1 column which can "shrink" these tens of peaks into a few peaks so that Brij 35 only occupies a small fraction of elution time, as shown in the Figure 8 in the link: http://www.dionex.com/en-us/webdocs/618 ... PN1963.pdf
This way the detection of the acidic drug is much less likely affected by the surfactant.

Alternatively, you can try the Acclaim Mixed-Mode WAX-1 column (http://www.dionex.com/en-us/webdocs/488 ... 021407.pdf) or other mixed-mode WAX column. I would use the mobile phase with low ionic strength (low buffer concentration, 1 to 5 mM NH4OAc), pH>5, and high organic solvent (say 70% MeCN or MeOH) first to elute the surfactant and keep the acidic drug. Hopefully the acidic drug will elute after the surfactant.

Please contact me if you need additonal information.