2 Replies Latest reply on Jan 17, 2018 7:26 AM by m4esti

    APCI - Gas Purity and Air (from the room) Interface

    beth_m

      We see reduced sensitivity in APCI source when polarity is negative. Technical support advised to loosen the findings that hold the nebulizer in place to introduce air into the source. The rational is that the gases are to pure going into the source causing charge ground in the source - no ions detected. There is no signal at all. The solution of leaving the nebulizer untightened does work; however, this is not a good permanent fix because the nebulizer housing is not secure and could cause inconsistency in results.  In general the APCI methodology we use has a long way to go. Please post tips and tricks on this specific problem and general suggestions about APCI methodology.

       

      Thank You,

      B

        • Re: APCI - Gas Purity and Air (from the room) Interface
          m4esti

          Hi Beth,

          Never heard of introducing air into the system. You might have a contaminated corona discharge needle where you are not getting a good charge on your gas and the excess air is giving more charges. I would check my connection where the corona needle plugs into and also abrasively clean my needle.

           

          Mitch

          • Re: APCI - Gas Purity and Air (from the room) Interface
            m4esti

            BTW what kind of samples are you running?

             

             

            Samples that work well by APCI are those that:

             

             

            1. Are small molecules, polar to non-polar: PAHs, PCBs, Fatty Acids, Phthalates.

             

            2. Contain heteroatoms: Ureas, benzodiazepines,carbamates.

             

            Samples to avoid for APCI are those that:

             

            1. Typically are multiply charged in solution: Proteins,peptides

             

            2. Are very thermally unstable: