I am running the EPA 504.1 method on a GC-ECD. When i run a standard i see peaks for all three analytes (EDB, 123TCP, DBCP), but when i run a blank i see a peak for 123TCP in all of the blanks i run. This is a dual column method and both columns are getting the peak for 123TCP at the same retention time 123TCp shows in the standard solution i run. The peak the shows in the blank for 123TCP isnt huge but big enough that i will never get a not detected result for this analyte. The columns are fairly new, about 3 months and not run regularly maybe a couple standards a week (in the middle of developing this method). What are some of the things i can look at to try to fix this issue?