Mecoprop or methylchlorophenoxypropionic acid (MCPP) is a common herbicide found in many weed-killing/fertilizer products. The EURL (European Union Reference Laboratory) placed mecoprop in an Analysis of Acidic Pesticides using QueChERS method. Obelisc R and Primesep 100 were used to retain mecoprop, each with unique selectivity due to multiple modes of separation. Obelisc R contains embedded ion-pairing groups and a long hydrophobic chain, while Primesep 100 contains acidic ion-pairing groups. Method is LC/MS compatible and capable of retaining many different pesticides.