contamination cannot be removed

Question

Hello Together, 
 I have a contamination (12-15min): it's also there when I change the device, make new eleuents and use different columns. The eluents are 0.1% H3Po4 in water and 0.1% H3Po4 in ACN. The contamination remains stable and comes with increasing gradient B. New containers were opened, purge frits were exchanged. Does anyone else have an idea? 
 
 Thanks 
 S

Andy Wright · Answer

my first comment is that the baseline doesn't look stable before you started this run, the second comment is about what happens around 30 minutes. is this the return to starting conditions at the end of a gradient? 
 Can you share more about the method? If it's a gradient, can you share the timetable? 
 I'd give the whole system a flush with the Agilent Flushing solution or, if you don't have that available, 100% IPA. 
 /Andy

contamination cannot be removed

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