Author:

Keywords:

Science & Technology, Physical Sciences, Life Sciences & Biomedicine, Chemistry, Analytical, Pharmacology & Pharmacy, Chemistry, (CD)-D-4, LC, Aminoglycosides, Ion-pairing reagents, Explorative study, TANDEM-MASS-SPECTROMETRY, PULSED ELECTROCHEMICAL DETECTION, CAPILLARY-ELECTROPHORESIS, QUANTITATIVE-DETERMINATION, MICROCHIP ELECTROPHORESIS, DETECTION CE-(CD)-D-4, FUNDAMENTAL-ASPECTS, GENTAMICIN SULFATE, STRAY CAPACITANCE, PART I, C(4)D, Anti-Bacterial Agents, Carboxylic Acids, Chromatography, Reverse-Phase, Hydrophobic and Hydrophilic Interactions, Indicators and Reagents, 0301 Analytical Chemistry, 1115 Pharmacology and Pharmaceutical Sciences, Analytical Chemistry, 3214 Pharmacology and pharmaceutical sciences, 3401 Analytical chemistry

Abstract:

The analysis of highly polar (often charged) compounds which lack a strong UV absorbing chromophore is really challenging. Despite the numerous analytical methods published, the demand for a simple, robust and cheap technique for their analysis still persists. Here, reversed phase (RP) liquid chromatography (LC) with capacitively coupled contactless conductivity detection (C(4)D) was explored for the first time as a possible method for separation and detection of various aminoglycoside (AMG) antibiotics which were taken as typical test compounds: tobramycin (TOB), spectinomycin, streptomycin, amikacin, kanamycin A and kanamycin B. C(4)D was performed using a commercially available as well as a laboratory made cell. As ion-pairing reagents (IPR) four perfluorinated carboxylic acids were used: pentafluoropropionic acid, heptafluorobutyric acid, nonafluoropentanoic acid (NFPA) and pentadecafluorooctanoic acid (PDFOA). 0.125mM NFPA-acetonitrile (ACN) (90:10) or 0.125mM PDFOA-ACN (70:30) as mobile phases were suitable to detect TOB with reasonable retention times. However, NFPA was preferred for practical reasons. Its applicable concentration range in the mobile phase was strongly restricted by loss of chromatographic performance at lower levels and excessive background conductivity at higher levels. Overall repeatability and robustness of the method were rather poor which was explained by the relatively low IPR levels. Selectivity between the tested AMGs was mainly influenced by the number of protonated amino groups per molecule making it impossible to separate compounds of equal net charges. Problems encountered with gradient elution, hydrophilic interaction liquid chromatography (HILIC) and separation at high pH without IPRs are also discussed.