p-Toluenesulfonic Acid (PTSA)

Organic acids were separated on a HILIC/cation-exchange column in HILIC/anion-exclusion mode. This column can be used for analysis of polar compounds in HILIC mode. If compounds are ionizable, additional mode of interaction can be added (cation-exchange or anion-exclusion).

Separation type: Liquid Chromatography Mixed-mode

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The majority of drugs in the pharmaceutical industry are administered in salt form. The presence of two counter-ions very often necessitates the use of two methods. The nature of these counterparts in drugs can be an inorganic cation and organic acid, inorganic anion and organic base, and organic cation and organic anion. Furthermore, the properties of the molecules will result in a differing stoichiometry. The task of simultaneous quantitation of counter-ions can be achieved by using mixed-mode columns. The general approach for analysis is based on properties of corresponding counter-ions. Hydrophobic basic drugs, like dextromethorphan, verapamil, trimipramine, and corresponding acidic counter-ions (chloride, chlorate, bromide, bromate, perchlorate, maleate, fumarate,tartrate, succinate, phosphate, citrate, benzosulfonate, toleuensulfonate) can be separated and quantitated in the same run on reversed-phase anion-exchange column. Basic hydrophobic drugs are retained by the reversed-phase mechanism, and counter-ions are retained by the reversed-phase and anion-exchange mechanism. Some polar counter-ions are retained only by the anion-exchange mechanism. Retention time and selectivity of HPLC separation of drugs and counter-ions can be achieved by changing the amount of acetonitrile and the amount of ions in the mobile phase. The detection technique depends on the properties of the counter-ions. In case of low or no UV activity, ELSD can be employed if the counter-ion forms a non-volatile salt with the mobile phase additive (ammonium formate). This HPLC method can be used for simultaneous quantitation of other basic drugs and counter-ions. The presence of two mechanisms of retention allows control over retention times of drug and counter-ion independently, and even allows a change of order of elution when necessary.

Ionic liquid is an ionic compound which is liquid at room (or close to room) temperature. Most of the ionic liquids are in a dynamic equilibrium where at any time more than 99.99% of the liquid is made up of ionic, rather than molecular, species. Room-temperature ionic liquids consist of bulky cation (for example, substituted imidazolium) compounds. A wide range of anions is used as counter ions in ionic liquids: organic and inorganic anions such as chloride, iodide, tetrafluoroborate, hexafluorophosphate, bistriflimide, triflate, tosylate. Ionic liquids are widely used as solvents in organic reactions. When products are isolated from ionic liquids, they need to be analyzed for residual ionic liquid content.
Because both constituents of the ionic liquid are very different in terms of charge and hydrophobic properties, it is impossible to analyze entire ionic liquids by traditional chromatography. An effective and universal method for analysis of ionic liquids is developed on an Obelisc R HPLC column. Components on the ionic liquids are retained based on ionic and hydrophobic interactions. Obelisc R column has both positively and negatively charged ionic groups, making it possible to retain and separate cations and anions of ionic liquids on one column. Method can be used for quantitative of various ionic liquids containing organic and inorganic ions. Retention time of basic component can be effectively adjusted by pH, stronger anionic and hydrophobic counter-ions might require higher buffer concentration. Composition can be monitored by combination of UV and ELSD or by LC/MS.