Analytical Separation of Closantel Enantiomers by HPLC

Closantel is an antiparasitic drug marketed in a racemic form with one chiral center. It is meaningful to develop a method for separating and analyzing the closantel enantiomers. In this work, two enantiomeric separation methods of closantel were explored by normal-phase high-performance liquid chromatography. The influences of the chiral stationary phase (CSP) structure, the mobile phase composition, the nature and proportion of different mobile phase modifiers (alcohols and acids), and the column temperature on the enantiomeric separation of closantel were investigated in detail. The two enantiomers were successfully separated on the novel CSP of isopropyl derivatives of cyclofructan 6 and n-hexane-isopropanol-trifluoroacetic acid (97:3:0.1, v/v/v) as a mobile phase with a resolution (Rs) of about 2.48. The enantiomers were also well separated on the CSP of tris-carbamates of amylose with a higher Rs (about 3.79) when a mixture of n-hexane-isopropanol-trifluoroacetic acid (55:45:0.1, v/v/v) was used as mobile phase. Thus, the proposed separation methods can facilitate molecular pharmacological and biological research on closantel and its enantiomers.

Separation and detection of aqueous atmospheric aerosol mimics using supercritical fluid chromatography–mass spectrometry

Atmospheric particles contain thousands of compounds with many different functional groups and a wide range of polarities. Typical separation methods for aqueous atmospheric systems include reverse-phase liquid chromatography or derivatization of analytes of interest followed by gas chromatography. This study introduces supercritical fluid chromatography–mass spectrometry as a separation method for the methylglyoxal–ammonium sulfate reaction mixture (a proxy for aqueous atmospheric aerosol mimics). Several column compositions, mobile-phase modifiers, and column temperatures were examined to determine their effect on separation and optimum conditions for separation. Polar columns such as the Viridis UPC2™ BEH column combined with a mobile-phase gradient of carbon dioxide and methanol provided the best separation of compounds in the mixture and, when coupled to an electrospray ionization tandem mass spectrometer, allowed for detection of several new masses in the methylglyoxal–ammonium sulfate reaction mixture as well as the possible identification of several isomers. This analysis method can be extended to other aqueous aerosol mimics, including the mixtures of other aldehydes or organic acids with ammonium or small amines.

Analysis of antisense oligonucleotides with the use of ionic liquids as mobile phase modifiers

The main goal of this study was the investigation of the impact of several ionic liquids, commonly used as free silanol suppressors, on the retention and separation of phosphorothioate oligonucleotides.

Usefulness of ionic liquids as mobile phase modifiers in HPLC-CV-AFS for mercury speciation analysis in food

Efficient Hg speciation analysis in different food samples was achieved with ionic liquids as mobile phase modifiers in HPLC-CV-AFS.