Quantitative extraction of multiclass antibiotic residues in cow milk utilizing salting-out assisted liquid-liquid extraction followed by liquid chromatographic determination

ABSTRACT

The salting-out assisted liquid–liquid extraction (SALLE) method with the liquid chromatography ultraviolet-visible detector (LC-UV) has been developed and validated for the simultaneous determination of seven antibiotic compounds of five different therapeutic classes (β-lactams), amoxycillin, ampicillin, penicillin G, (sulphonamides), sulfamethoxazole, (aminoglycosides) gentamicin, (fluoroquinolones) ciprofloxacin and (macrolide) erythromycin, in the cow milk samples. The LC conditions for separation of the selected antibiotic compounds were achieved with the reversed phase isocratic elution. The mobile phase consisted of 0.05 M Na₂HPO₄, acetonitrile and methanol (70:10:20 v/v/v). The mobile-phase flow rate was 1 mL min⁻¹ with the injection volume of 20 μL and all the seven standard compounds were eluted within 14 min. The developed analytical method has been validated for the linearity, precision, sensitivity, accuracy, specificity, decision limit (CCα), and detection capability (CCβ). Experimental parameters influencing the extraction efficiency were evaluated and optimised. Under the optimum experimental conditions, good linearity over wide concentration ranges was obtained with the coefficient of determination R² > 0.9989 for all the antibiotics. The limits of detection (LODs) and quantification (LOQs) ranged from 1.28 to 2.46 µg mL⁻¹ and 3.87–7.46 µg mL⁻¹, respectively. The relative standard deviations for the repeated analysis were below 8% indicating acceptable method precision. The accuracy study yielded satisfactory recoveries in the ranges 95.5–103% for the pure standard compounds and 83.8–112% for the spiked matrix-match milk samples. The results of the study revealed that the developed method is simple and fast and the SALLE method is appropriate for the simultaneous determination of targeted five multiclass antibiotic residues in the cow milk samples by LC-UV/Vis with a better efficiency.

KEYWORDS:

• Cow milk
• antibiotic residues
• salting-out assisted liquid-liquid extraction
• simultaneous determination

Acknowledgments

The authors express their gratefulness to the Department of Chemistry, College of Natural and Computational Sciences, Addis Ababa University and the Ethiopian Public Health Institute (EPHI) for providing laboratory facilities and financial support for sampling. Aynalem Lakew would like to thank the EPHI for sponsoring her doctoral studies.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All the data are included in the manuscript. There are no additional data with the authors.

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Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.