HPLC Separation of Benzenesulfonic and p-Toluenesulfonic Acids
Benzenesulfonic and toluenesulfonic acids are organic acids used in pharmaceutical industry as counter-ions for basic drugs. Both acids are hydrophilic in nature with strong acidic properties. Obtaining separation, retention and good peak shape with traditional reversed-phase columns is a challenging task. We developed robust mixed-mode approach for separation of benzenesulfonic acid and p-toluenesulfonic acid on a Primesep D reversed-phase anion-exchange column. Elution of these compounds is controlled by the amount of ions in the mobile phase and amount of acetonitrile. Both compounds are separated within 4 minutes and can be monitored by UV, ELSD, CAD or LC/MS. This column can be also used to analyze hydrophobic basic drugs by reversed-phase cation-exclusion mechanisms.
Benzenesulfonic AcidOrganic Acidsp-Toluenesulfonic Acid (PTSA)
HPLC Analysis of Components of Ionic Liquids by Mixed-Mode Chromatography
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.
1-Methyl-3-PropylimidazoliumBromideIonic LiquidMethylsulfonic AcidPerchloric AcidTFA (Trifluoroacetic Acid)p-Toluenesulfonic Acid (PTSA)
HPLC Analysis of Basic Drugs and Acidic Counter-Ions by Mixed-Mode Chromatography
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.
Benzenesulfonic AcidBromideChlorateChlorideCitric AcidDextromethorphanFumaric AcidMaleic AcidOrganic AcidsPerchloratePhosphoric AcidPyrilamineSuccinic AcidTartaric AcidVerapamilp-Toluenesulfonic Acid (PTSA)
HPLC Separation of Organic Acids in HILIC and Anion-Exclusion Mode on Primesep S2 Column
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).
||Primesep S2, 4.6x150 mm, 5 µm, 100A
||MeCN/H2O - 85/15%
||AmAc pH 5.0 15 mM
||ELSD, 50C UV 250 nm
|Class of Compounds
||Nucleosides, Hydrophilic, Ionizable
||Toluenesulfonic acid, Naphthalenedisulfonic acid, 3.5 DHBA, Ascorbic acid,
1,5-Naphthalenedisulfonic Acid3,5-Dihydroxybenzoic AcidAscorbic AcidOrganic Acidsp-Toluenesulfonic Acid (PTSA)