title: Exploring the possibilities of capacitively coupled contactless conductivity detection in combination with liquid chromatography for the analysis of polar compounds using aminoglycosides as test case.
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). 0.125 mM NFPA-acetonitrile (ACN) (90:10) or 0.125 mM 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.
authors.affiliation: Laboratory for Pharmaceutical Analysis, Faculty of Pharmaceutical Sciences, KU Leuven, Herestraat 49, O&N2, PB 923, B-3000 Leuven, Belgium; Semmelweis University, Department of Pharmaceutical Chemistry, Hőgyes Endre u. 9., H-1092 Budapest, Hungary; National Institute of Pharmacy, Zrínyi u. 3., PO Box 450, H-1051 Budapest, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Jankovics
authors.affiliation: Laboratory for Pharmaceutical Analysis, Faculty of Pharmaceutical Sciences, KU Leuven, Herestraat 49, O&N2, PB 923, B-3000 Leuven, Belgium.
authors.forename: Shruti
authors.initials: S
authors.lastname: Chopra
authors.affiliation: Laboratory for Pharmaceutical Analysis, Faculty of Pharmaceutical Sciences, KU Leuven, Herestraat 49, O&N2, PB 923, B-3000 Leuven, Belgium; Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Tripoli University, Libya.
authors.forename: Mohamed N
authors.initials: MN
authors.lastname: El-Attug
authors.affiliation: Laboratory for Pharmaceutical Analysis, Faculty of Pharmaceutical Sciences, KU Leuven, Herestraat 49, O&N2, PB 923, B-3000 Leuven, Belgium.
authors.forename: Deirdre
authors.initials: D
authors.lastname: Cabooter
authors.affiliation: Laboratory for Pharmaceutical Analysis, Faculty of Pharmaceutical Sciences, KU Leuven, Herestraat 49, O&N2, PB 923, B-3000 Leuven, Belgium.
authors.forename: Kris
authors.initials: K
authors.lastname: Wolfs
authors.affiliation: Semmelweis University, Department of Pharmaceutical Chemistry, Hőgyes Endre u. 9., H-1092 Budapest, Hungary.
authors.forename: Béla
authors.initials: B
authors.lastname: Noszál
authors.affiliation: Laboratory for Pharmaceutical Analysis, Faculty of Pharmaceutical Sciences, KU Leuven, Herestraat 49, O&N2, PB 923, B-3000 Leuven, Belgium.
authors.forename: Ann
authors.initials: A
authors.lastname: Van Schepdael
authors.affiliation: Laboratory for Pharmaceutical Analysis, Faculty of Pharmaceutical Sciences, KU Leuven, Herestraat 49, O&N2, PB 923, B-3000 Leuven, Belgium. Electronic address: Erwin.Adams@pharm.kuleuven.be.
authors.forename: Erwin
authors.initials: E
authors.lastname: Adams
mesh_terms: D000617:Aminoglycosides / Q000737:chemistry*; D000900:Anti-Bacterial Agents / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry; D056148:Chromatography, Reverse-Phase / Q000379:methods; D057927:Hydrophobic and Hydrophilic Interactions; D007202:Indicators and Reagents / Q000737:chemistry
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D002264:Carboxylic Acids; D007202:Indicators and Reagents
keywords: Aminoglycosides; C(4)D; Explorative study; Ion-pairing reagents; LC