Magnetic solid-phase extraction of amoxicillin and doxycycline from water and urine samples based on cetylpyridinium chloride–modified Fe₃O₄ nanoparticles followed by spectrophotometric determination

This research describes an easy, rapid, and inexpensive magnetic solid-phase extraction (MSPE) approach employing Fe₃O₄ magnetic nanoparticles modified with cetylpyridinium chloride (Fe₃O₄@CPC/MNPs) for extracting amoxicillin (AMX) and doxycycline (DOX) after derivatization with 4-chloroaniline as a color reagent. The azo-coupling of AMX and DOX with the color reagent in the alkaline medium caused yellow and yellow-orange azo dyes with maximum absorption wavelengths of 435 and 438 nm, respectively. The UV–Vis spectroscopy was utilized to determine the target analyte after the extraction procedure. Good linearities (R² > 0.99) in the concentration ranges of 0.03–4.50 and 0.05–6.00 µg/mL were obtained for AMX and DOX, respectively. The experimental detection limits of AMX and DOX were obtained as 0.01 and 0.02 µg/mL, respectively. The developed approach was effectively applied to pre-concentrate and quantify AMX and DOX in environmental water and urine samples.