LC and LC/MS Passivation Procedures to reduce metal levels?

Hi All,


We're running oligonucleotides by LC (1260) and LC/MS (1260 + 6130) and we're having issues with system cleanliness and passivation to reduce metal ion levels.


I've got the most recent tech note from 2007 that uses Water/MeCN and formic, followed by NaH2PO4 (attached - does anyone know the Tech Note number for this?) but I'm also looking for the following:


1) SN 01100-086: Passivation Procedure for Agilent 1100/1200 Instruments

2) SN 01100-016: Background Masses with HP 1100 Systems and MS Detection - Flushing Procedure


In addition, if anyone has any other recommended procedures, especially those that are MS compatible (I am not going to put nitric or phosphate into my MS source!!) I'd be really grateful.  Also, be interested if anyone has a view on using MS incompatible reagents through the nebuliser only, while it's removed from the source?


We are already using acid washed glassware to remove any metal ions from eluent container glass surfaces, and we are using ultratrace water.  We have a bioinert system on order to see how that helps, but we would still want to clean the MS.


Thanks in advance, Chris

  • Chris-


    It is unusual to have problems with metals with the oligonucleotide analysis.   Silca based columns can act as ion exchange columns and retain metal ions when used at about pH 7.  It can help to flush the columns with low pH solvents to displaced retained metal ions.



    The nebulizer and needle are stainless steel and it is not a bad idea to passivate the nebulizer also by placing the nebulizer disconnect from the nebulizer gas in a beaker.  Make sure the nebulizer is rinsed and cleaned up after the passivation.



    You might try calling the technical support line for help with your questions 800-227-9770 to clarify the details.