Validation of HPLC-UV Multi-Residue Method for the Simultaneous Determination of Tetracycline, Oxytetracycline, Spiramycin and Neospiramycin in Raw Milk

Abstract

The use of antimicrobial agents in livestock breeding is inevitable for prophylactic and treatment purposes, in order to maintain health and improve production of food products. However, this practice resulted in development of community resistance to antimicrobials due to residues found in livestock products. Milk is a key nutritional product that’s widely consumed for its high nutritional value. Maximum residue limits (MRL) for antimicrobials were established to minimize their consumption and increase the safety of food products. Although several research papers were validated for multi-class, multi-residue determination of antimicrobials, they were mainly LC coupled with MS/MS detection. This detection technique is expensive, so it doesn’t consider the economic aspects in low- and middle-income countries’ small regulatory laboratories. The proposed method enables the simultaneous determination of the residues of three widely used veterinary antimicrobials: Oxytetracycline (OTC), tetracycline (TTC) and spiramycin (SPI) besides its active metabolite neo-spiramycin (NSPI) in raw milk. Separation was performed on RP-C₁₈ column at flow rate 1.0 mL min⁻¹ and UV detection at 232 nm. Isocratic elution was done using mobile phase composed of 0.05 M phosphate buffer, pH 2.8 and acetonitrile, (8:2, v/v), respectively. Drug residues in raw milk were simply extracted using acetonitrile followed by centrifugation. The method was found linear across the ranges of 20–1000 ng mL⁻¹ for TTC and OTC, and 100–1000 ng mL⁻¹ for SPI and NSPI. The proposed method was found sensitive to low detection and quantification limits covering the MRL of studied drugs with LOD of 5.0 ng mL⁻¹ for OTC and TTC and 16.0 ng mL⁻¹ for SPI and NSPI.