Dealing with high salt samples

Discussions about CE, MEKC and related topics

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I am running into a bit of a snag with CE. A lot of my samples are very high in salt mainly NaCl. I work with dried flavor powders. They average 25% weight NaCl but can go even higher. Anyways the high salt is causing terrible peak shape from destacking and significant migration time shifts.

I am running a method for Inosinate, Guanylate, and Thiamine on a 50um-50cm cap using 60 mmol/L borate/2-amino-2-methyl-1-propanol-80 mmol/L sodium dodecyl sulfate (pH 9.6) BGE. My LOQ is 10ppm injection so with a 1/10 dilution my sample LOQ is 100ppm.

Is there anything I can do other than dilute the sample more and lose more sensitivity? I am playing with increasing the borate/AMP to as high as 500mM though that will slow the EOF and may cause heating issues. I am also unsure of the solubility of the SDS in that high salt.
Maybe you could do a dialysis?
I've tried a variety of things so far. I tried the acetonitrile method using 66% acetonitrile in the sample. It reduced the migration time significantly and thiamine disappeared. I suspect it may have crashed out of solution.

I've been trying water plugs, electrokinetic injection etc.

I also tried upping the buffer concentration but it caused issues with the baseline, and of course high current and high migration times due to reduction in the EOF.

I am reading stuff on stacking.

I guess I could worse case scenario do ion exchange SPE but I'd have to do two because thiamine is cationic and Inosinate and guanylate are anionic.
Haven't really found a solution to high salt other than dilute and use the highest ionic strength buffer possible (can't go much higher than 100mM for my method).

For sample cleanup I have had good results with methanol/water:chloroform protein precipitation followed by blow down and redissolution in water. It has the added benefit of removing the fat and many nonpolar food/flavor compounds as well.
4 posts Page 1 of 1

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