Use of a Hepta-Tyr antibiotic modified silica stationary phase for the enantiomeric resolution of d,l-loxiglumide by electrochromatography and nano-liquid chromatography

Hepta-Tyr antibiotic modified silica stationary phase was used for the chiral resolution of d,l-loxiglumide, a new drug under investigation proposed for the treatment of gastrointestinal diseases. The chiral stationary phase was packed into fused silica capillaries of 75 μm i.d. for a length of only 7 cm and used for both capillary electrochromatography (CEC) and nano-liquid chromatography (nano-LC) running the experiments with the same instrumentation; in order to increase the electroosmotic flow (EOF) the antibiotic stationary phase was mixed with amino-silica particles (3:1, w/w) generating a relatively high reversed EOF. The enantiomeric resolution of loxiglumide by CEC was strongly influenced by several experimental parameters such as applied electric field, mobile phase composition, capillary temperature, etc. Optimum experimental conditions were found applying 15 kV at 20 °C and eluting with acetonitrile–sodium phosphate buffer at pH 6 (1:1, v/v). The same capillary was tested for nano-LC experiments. Good chiral separation of loxiglumide was achieved selecting the appropriate mobile phase considering the type and concentration of organic modifier. The nano-LC optimised method was therefore validated and applied to the analysis of a pharmaceutical formulation declared to contain only d-loxiglumide.