Halide ions are usually analyzed by ion-chromatography with a conductivity detector. Mixed-mode chromatography in combination with ELSD is offering a valuable alternative to ion-chromatography with conductivity detection. Chloride, bromide and iodide were separated on a Primesep SB mixed-mode anion-exchange column. Mobile phase is compatible with ELSD and LC/MS.

Ion chromatography is usually used for analysis of hydrophilic organic and inorganic ions. Same separation can be achieved on HILIC/mixed-mode Obelisc N HPLC columns. Obelisc N HPLC columns have very polar groups on their surface: one of the groups is basic and the other acidic. In case of low organic concentration, two groups are connected by hydrophilic linker. Obelisc N column can be used as cation-exchange and anion-exchange column. This allows to separate positively and negatively charged molecules in one run. Five anions (chloride, bromide, methanesulfonate, nitrate and perchlorate) along with one cation (sodium) were separated in one run. Method is compatible with ELSD, CAD and LC/MS and can be used for analysis of various hydrophilic and hydrophobic cations and anions in one HPLC run.

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.