Simultaneous determination of six fluoroquinolones in milk by validated QuEChERS-DLLME HPLC-FLD

Abstract

Fluoroquinolones (FQs) in milk are not destroyed at high temperature and their stability increases the risk of human exposure and may cause food-borne illness. The present study reports the use of QuEChERS-dispersive liquid–liquid micro extraction (DLLME) for the extraction and determination of six FQs (marbofloxacin, norfloxacin, ciprofloxacin, difloxacin, enrofloxacin and danofloxacin) in whole milk samples. Linearity was obtained over a concentration range of 0.25, 0.5, 1.0, 2.0 and 4 maximum residue limits (MRLs) with regression coefficients ranging from 0.9916 to 0.9993. Intra and inter-day (n = 3) repeatability expressed as the percentage of the relative standard deviation (RSD%) were between 2.1–11.1% and 1.6–6.5%. LOQs were below 2.5 µg kg⁻¹ for danofloxacin and 15 µg kg⁻¹ for the other FQs. The recoveries in spiked milk samples at 0.5, 1 and 2 MRLs ranged from 69.2% to 104.8%. The validated method was successfully applied for the determination of FQs in milk samples, and the mean contamination of samples was lower than the European legal limits.