Determination of α-tocopherolquinone in human serum samples by liquid chromatography with fluorescence detection and on-line post-column derivatization

ABSTRACT Clinicians need a better way to accurately monitor the concentration of antimicrobials in patient samples. In this report, we describe a novel, low-sample-volume method to monitor the azole-class antifungal drug posaconazole, as well as certain other long-chain azole-class antifungal drugs in human serum samples. Posaconazole represents an important target for therapeutic drug monitoring (TDM) due to its widespread use in treating invasive fungal infections and well-recognized variability of pharmacokinetics. The current “gold standard” requires trough and peak monitoring through high-pressure liquid chromatography (HPLC) or liquid chromatography-tandem mass spectroscopy (LC-MS/MS). Other methods include bioassays that use highly susceptible strains of fungi in culture plates or 96-well formats to monitor concentrations. Currently, no method exists that is both highly accurate in detecting free drug concentrations and is also rapid. Herein, we describe a new method using reduced graphene oxide (rGO) and a fluorescently labeled aptamer, which can accurately assess clinically relevant concentrations of posaconazole and other long-chain azole-class drugs in little more than 1 h in a total volume of 100 µl. IMPORTANCE This work describes an effective assay for TDM of long-chain azole-class antifungal drugs that can be used in diluted human serum samples. This assay will provide a quick, cost-effective method for monitoring concentrations of drugs such as posaconazole that exhibit well-documented pharmacokinetic variability. Our rGO-aptamer assay has the potential to improve health care for those struggling to treat fungal infections in rural or resource-limited setting.

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Multiresidue Determination of Fluoroquinolones in Eggs

Journal of AOAC International ◽

10.1093/jaoac/83.6.1306 ◽

2000 ◽

Vol 83 (6) ◽

pp. 1306-1312 ◽

Cited By ~ 17

Author(s):

Marilyn J Schneider ◽

Dan J Donoghue

Keyword(s):

Liquid Chromatography ◽

Fluorescence Detection ◽

Small Volume ◽

Reversed Phase ◽

Reversed Phase Liquid Chromatography ◽

Trace Enrichment ◽

On Line ◽

Phase Liquid ◽

Multiresidue Determination

Abstract A multiresidue method was developed for the determination of fluoroquinolones in eggs. Extraction of eggs with ammoniacal acetonitrile was followed by liquid–liquid defatting, solvent evaporation, and redissolution in a small volume of buffer. The fluoroquinolones were further purified by on-line microdialysis, concentrated on a trace enrichment column, and separated by reversed-phase liquid chromatography with fluorescence detection. Norfloxacin (NOR), ciprofloxacin (CIP), and sarafloxacin (SAR) were extracted from fortified eggs over a range of 2–200 μg/kg, with recoveries of 65.7–78.9%, 65.6–77.1%, and 67.6–110%, respectively. Enrofloxacin (ENRO) was extracted over a range of 1–100 μg/kg, with recoveries of 71.5–86.7%, whereas desethylene ciprofloxacin (DCIP) and danofloxacin (DANO) were extracted over a range of 0.2–20 μg/kg, with recoveries of 68.7–90.7% and 76.0–93.8%, respectively. The limits of quantitation for the 6 fluoroquinolones were as follows: DCIP and DANO, 0.3 μg/kg; ENRO, 1 μg/kg; NOR and CIP, 2 μg/kg; and SAR, 3 μg/kg. Both SAR and ENRO incurred eggs were also successfully analyzed using this method.

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