Carboxin or carboxine is an oxathin fungicide considered by the EURL (European Union Reference Laboratory) to be a target pesticide. It was placed on a Target Pesticide List for the EUPT-CF9 2015 (European Union Proficiency Test for Cereals and Feeding stuff). A method for separating carboxin was developed for Primesep 100 and Obelisc R columns. Both columns are mixed-mode offering unique retention tuning. Obelisc R contains ion-pairing groups and a long hydrophobic chain, while Primesep 100 contains embedded acidic ion-pairing groups. Method is LC/MS compatible and can be used on many pesticides and herbicides.