Contamination by quinolones cleverly caught by MLC

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  • Published: Oct 1, 2017
  • Author: Ryan De Vooght-Johnson
  • Channels: HPLC
thumbnail image: Contamination by quinolones cleverly caught by MLC

Antibiotic residues in meat need monitoring

Veterinary antibiotics are commonly given to food-producing animals in many countries, both in response to disease and as a preventative measure, which also has the effect of increasing animal weight. There are concerns about residues in meat causing allergies and changing the composition of the human intestinal bacterial population. The residues may also give rise to antibiotic-resistant bacteria, which are an increasing problem across the world. EU regulations impose strict limits on the permitted residue levels in meat, necessitating the development and validation of accurate analytical methods.

Existing methods of analysis typically use reversed-phase HPLC; however, complicated extraction procedures are needed to separate interfering components arising from the meat matrix. Researchers from Jaume I University developed a new method using micellar liquid chromatography (MLC). In this variety of HPLC, a surfactant is used to produce a mobile phase containing micelles. A previous paper in the journal ‘Food Chemistry’ described the application of the method to pork and beef, while the current paper describes its use for turkey, chicken, duck, lamb, rabbit, goat and horse meat. Four quinolone antibiotics were measured: danofloxacin, oxolinic acid, enrofloxacin and ciprofloxacin; the latter compound is usually used as a human, rather than a veterinary, antibiotic, but can be found in meat because it is a metabolite of enrofloxacin.

MLC used to measure antibiotic residues in meat

Minced samples of each type of meat were spiked with quinolone antibiotic standards and extracted with 0.05 M aqueous sodium dodecyl sulphate solution at pH 3, using magnetic stirring followed by sonication. The solids were filtered off prior to MLC.

The chromatography employed an Agilent HP1100 system, fitted with a Scharlab Kromosil C18 column. The column was run under isocratic conditions with a mobile phase consisting of 0.05 M aqueous sodium dodecyl sulphate solution (0.01 M in sodium dihydrogen phosphate) containing 7.5% 1-propanol and 0.5% trimethylamine; the mixture was taken to pH 3 with a few drops of hydrochloric acid, sonicated and then filtered prior to use. Fluorescence detection (FLD) was used, with an excitation wavelength of 260 nm and an emission wavelength of 366 nm for the first portion of the run (0 to 8 minutes) followed by an excitation wavelength of 280 nm and emission at 455 nm for the remainder of the run (8 to 22 minutes). Under these optimised conditions, the four antibiotics were clearly separated from each other and were clear of interfering peaks in all seven types of meat.

The method gave good linearity and repeatability. It also gave high sensitivity, with limits of detection (LOD) ranging from 0.004 to 0.02 mg/kg of sample and limits of quantification (LOQ) ranging from 0.01 to 0.05 mg/kg. The maximum residue limits (MRL) given by EU regulations were either 0.1 or 0.2 mg/kg, depending on the antibiotic and meat. Decision limits (CCα) and detection capabilities (CCβ) were calculated, and these were found to give adequate discrimination of samples with contamination levels close to the MRL. The method was successfully validated in line with EU regulations.

MLC and FLD give accurate detection of quinolone antibiotics

The combination of MLC and FLD gave good detection of quinolone antibiotics, with clear separation from interfering peaks. The new method avoids the lengthy and complicated sample preparation procedures necessary with reversed-phase HPLC of antibiotic residues in meat samples. MLC deserves to be more widely used, as it can give good results in cases where matrix components tend to give interference with standard reversed-phase HPLC, and it also can reduce the usage of organic solvents, a definite advantage in laboratories with a high throughput of samples.

Related Links

Electrophoresis, 2017, 38, 2011-2017. Peris-Vicente et al. Validation of a procedure to quantify oxolinic acid, danofloxacin, ciprofloxacin and enrofloxacin in selected meats by micellar liquid chromatography according to EU Commission Decision 2002/657/EC.

Food Chemistry, 2017, 221, 1277-1284. Terrado-Campos et al. Determination of oxolinic acid, danofloxacin, ciprofloxacin, and enrofloxacin in porcine and bovine meat by micellar liquid chromatography with fluorescence detection.

Wikipedia, Micellar Liquid Chromatography

Article by Ryan De Vooght-Johnson

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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