# Sustainable Anisaldehyde-Based Natural Deep Eutectic Solvent Dispersive Liquid–Liquid Microextraction for Monitoring Antibiotic Residues in Commercial Milk and Eggs: A Comprehensive Evaluation of Greenness, Practicality, Analytical Performance and Innovation

## TL;DR

This study introduces a green and efficient method to detect antibiotic residues in milk and eggs using a sustainable solvent and advanced analytical techniques.

## Contribution

A new biodegradable natural deep eutectic solvent-based microextraction method for antibiotic residue analysis in food.

## Key findings

- The method achieved high recoveries (89.5–98.7%) and good linearity (R2 ≥ 0.9982) for antibiotic detection.
- Sulfamethoxazole was the most frequently detected antibiotic in 90% of egg and 70.8% of milk samples.
- The method was confirmed as green, practical, and innovative using ten evaluation metrics.

## Abstract

The widespread use of antibiotics in human medicine, veterinary care, and livestock production has resulted in their frequent detection in diverse environmental and food matrices, making continuous surveillance of antibiotic residues in food products essential for consumer protection. In this study, a sustainable analytical method based on dispersive liquid–liquid microextraction (DLLME) coupled with UHPLC–MS/MS was developed for the trace determination of sulfamethoxazole, sulfadimethoxine, and enrofloxacin in commercial cow milk and chicken eggs. A natural deep eutectic solvent (NADES) composed of anisaldehyde and octanoic acid (2:1, molar ratio) was employed as a biodegradable extraction solvent, and key extraction parameters were systematically optimized. Under optimized conditions, the method demonstrated excellent linearity (R2 ≥ 0.9982), recoveries of 89.5–98.7%, and RSDs ≤ 6.04%. Application to 44 commercial samples from the Saudi market revealed sulfamethoxazole as the most frequently detected antibiotic, occurring in 90% of egg samples (2.17–13.76 µg kg−1) and 70.8% of milk samples (0.26–26.67 µg L−1). A comprehensive evaluation using ten metrics confirmed the method’s greenness, practicality, analytical performance, and innovation. Overall, the proposed NADES–DLLME–UHPLC–MS/MS approach offers a rapid, cost-effective, and environmentally friendly alternative for routine monitoring of antibiotic residues in food matrices.