Mepiquat is a plant growth regulator that is monitored by EPA in water. It is a quaternary amine that is very polar in nature. Mepiquat and other hydrophilic amines are not retained on reversed-phase columns, and produce poor peak shape due to residual silanol interactions. Ion-pairing reagent is required to retain mepiquat. Ion-pairing reagents are not compatible with LC/MS detection and most environmental application require high sensitivity methods to determine very low level of contaminants. Obelisc R mixed-mode column can be used for EPA methods for determination of common pesticides, herbicides and insecticides where analysis of very polar ionic compounds is required.