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MASS SPEC - MASS APPEARS TWICE IN SAME SPECTRUM

  • #1
    Registered Users Posts: 22 ✭✭✭ Kina


    Hi all,

    Just made a product as part of a Research project, and after running through LC-MS, the parent ion mass has appeared twice. I personally have never seen this happen before, so have you any ideas? A dimer issue has been suggested.


Comments



  • Actually, I have seen this. Before I did my PhD in cancer, I worked a few months at the Dept. of Chemistry at the Uni of York and was doing MS routinely. I saw - numerous times - ion masses that were multiple-times the parent (i.e. some even more than double). I was however working with sugar molecules (hexa- and penta-saccharides).

    Which molecules are you working with?




  • Are they same using TOF? Are they same using high mass accuracy?




  • It sounds like something extremely hydrophobic is lodged on your column, for example detergent. This will make your column a non homogeneous surface and will cause the double banding you have described. If you or anyone else are running samples always spin filter to remove detergent. Give the column a complete flush through for several hours but depending on the detergent the column may need to be replace. They are notoriously difficult to remove once they stick onto a column.




  • It sounds like something extremely hydrophobic is lodged on your column, for example detergent. This will make your column a non homogeneous surface and will cause the double banding you have described. If you or anyone else are running samples always spin filter to remove detergent. Give the column a complete flush through for several hours but depending on the detergent the column may need to be replace. They are notoriously difficult to remove once they stick onto a column.

    If you have detergents, you would probably see it in the spectra though?

    I can only speak from biological sample analysis, but the more common detergents (or detergent products) have common diagnostic ions.


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