Toluene

Mixed-mode HPLC columns allow to analyze compounds with drastically different properties in one run. Acidic, basic, and neutral compounds can be separated in one run using either isocratic or gradient conditions. In this application, neutral hydrophilic (uracil, phenol and hydroquinone), neutral hydrophobic (toluene), hydrophilic acidic (benzoic acid), hydrophilic basic (lutidine) and hydrophobic basic (amitriptyline) are separated using gradient of ACN. Neutral compounds are retained by reversed-phase mechanism, hydrophilic acidic compound become more hydrophobic at lower pH and retain by reversed-phase mechanism too. Basic compounds are retained by cation exchange mechanism, and hydrophobic basic compounds are retained by reversed-phase and cation-exchange mechanisms. All compounds are resolved within 17 minutes on a short column. Method can be applied to various polar and hydrophobic compounds, which can be separated on one column and in one run. Mixed-mode columns can operate in single or combination of several modes: reversed-phase, ion-exchange, ion-exclusion and HILIC. This mixed-mode HPLC column can be used as a general column for separation of wide range of compounds.

Primesep 100 and Primesep 200 columns can be used as a universal column for analysis of wide range of compounds. These mixed-mode reversed-phase ion-exchange HPLC columns can provide a valuable alternative to traditional reversed-phase column. Amines, amino acids, quaternary amines, and various zwitter-ions can be analyzed along with hydrophobic compounds and organic and inorganic counter-ions. In this application, 8 compounds with different hydrophobic, hydrophilic, basic and acidic properties are separated based on their properties. Primesep 100 column is a mixed-mode HPLC column with a C12 carbon chain and carboxylic acid on the surface with pKa of 1. Primesep 200 column is a mixed-mode HPLC column with a C12 carbon chain and carboxylic acid on the surface with pKa of 2. These columns can be used with 100% organic (ACN) and 100% aqueous mobile phases. This HPLC method can be adopted as a generic and robust approach for analysis of acidic, basic and neutral compounds within the same run.

Parabens are common preservatives in pharmaceutical and cosmetic industries. They are esters of p-hydroxybenzoic acid. Method for separation of methyl paraben, propyl paraben, benzonitrile and toluene was developed on a Obelisc R column. All four compounds are neutral and are retained by reverse-phase mechanism. In case of reversed-phase stationary phase, no effect of pH is observed. Retention time for all four compounds changes on an Obelisc R column when pH is changed. pH of the mobile phase affects ionization state of stationary phase. Obelisc R column has C12 carbon chain and carboxylic acid with pKa of 4. At lower pH (pH 2, TFA), carboxylic acid of stationary phase is not ionized and thus adds hydrophobicity to stationary phase. Obelisc R column can be used for analysis of basic, acidic and neutral compounds with suitable detection techniques – UV, ELSD, CAD, LC/MS.

Mixed-mode chromatography allows separating, in single run, compounds with vastly different properties. A method for separation of amino acids (cysteine, methylcysteine, cystine and dimethylcysteine) in the presence of carboxylic acid (benzoic) and hydrophobic neutral compounds was developed on Primesep 100 mixed-mode column. At lower pH ionization of carboxylic acids is suppressed. Amino acids are retained as basic compound based on reverse phase and cation exchange mechanisms. Carboxylic acids are retained on this column based on weak reverse phase mechanisms. Neutral compounds are retained by reverse phase mechanism as on any other column. Retention time of basic, zwitter-ionic and hydrophobic compound can be adjusted by manipulation of mobile phase composition. ELSD, UV or LC/MS detection can be used based on the properties of analytes and mobile phase selection.

Separating basic, acidic and zwitterionic compounds in one run in reverse-phase HPLC can be very challenging. The methods might require the use of ion-pairing reagents and complex gradients that can make MS-compatibility difficult. Obelisc R column which has both positive and negative ion-pairs embedded in the stationary phase allows for fine tuning and separation of a wide range of compounds with different ionic properties. Acids, bases, amino acids and neutral compounds were separated isocratically in one run using a simple MS-compatible mobile phase of acetonitrile (ACN) and water with Ammonium Acetate (AmAc) buffer. Can also be UV detected at 250nm.

Primesep 100 separates a mixture of amino acids (tyrosine, phenylalanine), organic acids (benzoic acid, mandelic acid), amines (benzylamine, pyridine), and neutrals (benzonitrile, toluene) in one HPLC run by combining reversed-phase, cation-exchange, and polar interactions. The method is tunable and peak order can be changed significantly by adjusting acetonitrile and trifluoroacetic acid concentrations. The separation method uses a mobile phase mixture of water, acetonitrile (MeCN, ACN) and trifluoracetic acid (TFA) and compatible with UV, mass spec (LC/MS) and evaporative light scattering (ELSD) detection.

Primesep 100 separates a mixture of polar and nonpolar compounds in one analytical run. The amino acid cysteine; amino acid derivatives L-cystine, 2,2-dimethylcystine, and 2-methylcysteine; the polar acid benzoic acid; and the nonpolar neutral toluene are separated by a gradient using a combination of polar and hydrophobic interactions. The separation method uses a mobile phase mixture of water, acetonitrile (MeCN, ACN) and sulfuric acid (H2SO4) with UV detection at 210 nm.