LAUSR

Owing to their pronounced polarity, hydrophilic interaction liquid chromatography (HILIC) can be considered as the elective choice for the LC analysis of aminoglycoside (AG) antibiotics. In the present work, a gradient program was optimized for the first time with a diol-type stationary phase and an evaporative light scattering detector (ELSD), thus allowing the almost complete separation of the nine analysed AGs: spectinomycin, dihydrostreptomycin, streptomycin A, gentamicin C1, amikacin, kanamycin A, paromomycin, apramycin and neomycin. In the optimized analysis conditions, analyte retention was found to be governed by a multimodal mechanism encompassing electrostatic, partitioning and hydrophilic interactions. However, the gradient mode of elution complicated a deep understanding of the influence of each contribution on the retention behaviour. The developed HILIC-ELSD method was applied for the analysis of commercial tablets containing neomycin co-formulated with the polypeptide antibiotic bacitracin. The method was fully validated according to the guidelines enshrined in the International Conference on Harmonization (ICH). The use of the diol-type stationary phase was well suited for implementing a successful 2D-HPLC system. Indeed, in order to cope with the absence of chemoselectivity for the couples amikacin/kanamycin and paromomycin/apramycin, a successful 2D-HPLC method was implemented with the "heart-cut" approach and the use of either heptafluorobutyric (for the former) or perfluorooctanoic acid (for the latter) as the ion-pair reagent in the second RP-LC dimension.