Chromatographic analysis of bromhexine and oxytetracycline residues in milk as a drug analysis medium with greenness profile appraisal

Abstract

Tetracyclines are frequently employed in animal husbandry. Bromhexine is a mucolytic drug that improves the efficacy of tetracyclines. It has been reported that residues of tetracyclines in milk may have negative effects on humans. Two versatile and accurate methods were developed for concurrent analysis of oxytetracycline (OTC) and bromhexine (BR) residues in spiked milk samples. Sample preparation was carefully considered for extraction and cleanup using the ecofriendly chemicals acetic acid, 0.1 N EDTA and ethanol or methanol. The first method was a TLC-densitometric method in which TLC plates previously treated with 10% EDTA (pH 9 with 40% sodium hydroxide) were used as a stationary phase. A solvent mixture of methanol : methylene chloride : 2% aqueous acetic acid (8 : 2 : 0.5, by volume) was the developing system, and detection was carried out at 254 nm. Metformin was used as the internal standard, and linearity was achieved in the ranges of 0.2–10 and 0.04–2 μg per band for OTC and BR, respectively. The second method was a RP-HPLC method; separation was performed on a C18 column using an isocratic mixture of ethanol : 7.5% aqueous acetic acid (70 : 30, v/v). Separation was achieved within 10 minutes, and linearity was proven in the ranges of 0.05–50 and 0.05–30 μg mL⁻¹ for OTC and BR, respectively. Diclofenac sodium was used as an internal standard. The proposed methods were validated in accordance with the FDA Center for Veterinary Medicine guidelines. Moreover, the performance and health and environmental impacts of the methods were evaluated using several greenness metrics, namely, the National Environmental Methods Index (NEMI), modified NEMI, Green Analytical Procedure Index (GAPI), Analytical Eco-Scale and Analytical GREEnness (AGREE) metric approaches. All the obtained results proved the validity of the developed methods concerning its performance and ecological effects. The methods can be used to investigate the presence of OTC residues in various marketed milk samples to maintain public health.