Capillary electrochromatography‐mass spectrometry for the determination of 5‐nitroimidazole antibiotics in urine samples

Abstract

The separation of eight antibiotics belonging to 5-nitroimidazole family was carried out by means of CEC coupled with MS. Preliminary experiments were carried out with ultraviolet detection in order to select the proper stationary and mobile phase. Among the different stationary phases studied (namely Lichrospher C18, 5 μm particle size; Cogent(TM) Bidentate C18, 4.2 μm; Pinnacle II™ Phenyl, 3 μm; Pinnacle II™ Cyano, 3 μm), Cogent™ Bidentate C18 (4.2 μm) gave the best performance. For CEC-MS coupling, a laboratory assembled liquid-junction-nano-spray interface was used. In order to achieve a good sensitivity, special attention was paid to both optimization of the sheath liquid composition as well as selection of the injection mode. Under optimized CEC-ESI-MS conditions, the separation was accomplished within 22 min by using a column packed with a mixture of Bidentate C18:Lichrospher Silica-60 (5 μm) 3:1 w/w, an inlet pressure of 11 bar, a voltage of 15 kV, and a mobile phase composed by 45:10:45 v/v/v ACN/MeOH/water containing ammonium acetate (5 mM pH 5). A combined hydrodynamic and electrokinetic injection of 8 bar, 15 kV, and 96 s was adopted. The method was validated in terms of repeatability and intermediate precision of retention times and peak areas, linearity, and LODs and LOQs. RSDs values were <2.9% for retention times and <16.1% for peak areas in both intraday and interday experiments. LOQ values were between 0.09 and 0.42 μg/mL for all compounds. Finally, the method was applied to the determination of three most employed 5-nitroimidazole antibiotics (metronidazole, secnidazole, and ternidazole) in spiked urine samples, subjected to a SPE procedure. Recovery values in the 67-103% range were obtained. Furthermore, for the selected antibiotics, CEC-MS(2) spectra were obtained providing the unambiguous confirmation of these drugs in urine samples.

Determination and Identification of Antibiotic Drugs and Bacterial Strains in Biological Samples

“…The limit of the detection of the assay was from 0.09 to 0.42 µg/mL [90]. Another report described the CE [83][84][85][86].…”

“…In 2015, a method of coupling CEC with mass spectrometry was also described. Hernández-Mesa et al [90] determined five nitroimidazoles in urine samples. After SPE, drugs were analyzed by using a column packed with a mixture of Bidentate C18:Lichrospher Silica-60 (5 µm) and the background electrolyte (BGA) composed by acetonitrile, methanol and water (45:10:45 v/v/v).…”

An overview to nano‐scale analytical techniques: Nano‐liquid chromatography and capillary electrochromatography

“…The L‐J used in CEC was realized by machining a small block of polycarbonate. The packed capillary column was connected with a tip capillary into the electrode compartment containing a ionization liquid that was pressurized hydrodynamically at 20–30 mbar . Good results were obtained for the separation of non steroidal anti‐inflammatory drugs or chiral drugs .…”

Recent advances in microscale separation

“…Hernández‐Mesa et al. prepared capillary column packed with a mixture of Bidentate C18 for separation of eight antibiotics belonging to 5‐nitroimidazole family by means of CEC coupled with MS. LOD values were between 0.09 and 0.42 μg/mL for all compounds.…”