Total sulfonamides determination in bovine milk using smartphone-based digital images

Abstract

Sulfonamides are low-cost synthetic antimicrobials that are widely used in both veterinary and human medicine to treat diseases and control and prevent infections. Long periods of exposure to sulfonamides may cause adverse effects such as heart problems, allergic reactions, and hepatic and digestive dysfunction in humans. The maximum residue limit established for the total quantity of sulfamethazine, sulfadimethoxine, and sulfathiazole in bovine milk is 100 μg L−1. This study aims to employ dispersive liquid–liquid microextraction (DLLME) as a green chemistry technique for the extraction of total sulfonamides in bovine milk samples. The procedure involves the formation of an imino salt, posterior DLLME with 1-butanol, and measurement using digital images. A linear response was observed between 50 and 1000 µg L−1 for total sulfonamides, described by the equation: Analytical signal = 3.02 + 0.03 C (µg L−1) (R2 = 0.999). The coefficient of variation (n = 11; 250 µg L−1 total sulfonamides) and the detection limit were estimated to be 0.49% and 20 µg L−1, respectively. For 0.50 mL of milk sample, 0.75 mg p-DAC, 17.30 mg SDS, 49.20 mg of trichloroacetic acid, and 0.50 mL 1-butanol were consumed. Recovery tests using the addition-recuperation method were performed, achieving 88 and 100% recovery. The results agreed with those obtained by a HPLC procedure at 95% confidence level.