Simultaneous analysis of antibiotics in biological samples by ultra high performance liquid chromatography–tandem mass spectrometry

• Simultaneous analysis of more than 21 antibiotics in biological fluids.
• Fast and simple sample treatments were applied, increasing sample throughput.
• UHPLC-MS/MS analyses were performed in less than 6 min.
• The highest concentrations of antibiotics were found in urine.

A rapid and reliable multiclass method was developed for the simultaneous analysis of 21 antibiotics (beta-lactams, aminoglycosides, penicillins, cephalosporins, carbapenems or quinolones) in urine, serum, cerebrospinal fluid (CSF) and bronchial aspirations by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS). Prior to chromatographic determination, the analytes were extracted from human biological fluids by simple sample treatments, which imply dilution, liquefaction, or protein precipitation. Several chromatographic conditions were optimized in order to obtain a fast separation (<6 min for each chromatographic run). MS/MS conditions were evaluated in order to increase selectivity and sensitivity and all compounds were detected in electrospray (ESI) positive ion mode, except clavulanic acid and sulbactam, which were monitored in negative ion mode. The developed method was validated in terms of linearity, selectivity, limits of detection (LODs) and quantification (LOQs), trueness, repeatability and interday precision. The LOQs ranged from 0.01 to 1.00 mg/L for urine, serum and CSF. In case of bronchial aspirations, the LOQs were between 0.02 and 0.67 mg/kg. In all matrices the recovery results were in the range 70–120% and interday precision was lower than 25%. Finally, the optimized method was applied to the analysis of biological samples from 10 patients in the intensive care unit (ICU) of a hospital located in Almeria (Spain). Several antibiotics (e.g., amoxicillin, tobramycin, levofloxacin, or linezolid) were found in the studied samples, observing that the highest concentrations were obtained in urine samples.

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