This work describes a simple and straightforward magnetic solid phase extraction (MSPE) approach based on benzalkonium chloride-modified silica-coated magnetite nanoparticles (Fe₃O₄@SiO₂@BZC). The developed extraction method was employed for extracting doxycycline hyclate (DOX) from water and urine samples after derivatization with procaine benzylpenicillin (PP) as a color reagent. An orange azo dye with a maximum adsorption wavelength (λ_max) of 440 nm was produced by the azo-coupling of DOX with the color reagent in the alkaline medium. The analytical conditions were optimized carefully, including the reagent and surfactant volumes, the amount of sorbent, the extraction time, and the pH of the solution. The developed extraction approach achieved pre-concentration and enrichment factors of 47 and 25, respectively. UV–vis spectroscopy was utilized to determine the target analyte after the extraction step. A good linearity (R² > 0.99) in the concentration range of 0.08–3.00 μg/mL was achieved. Detection and quantification limits of DOX were found to be 0.01 and 0.04 μg/mL, respectively. The suggested method was successfully applied to the extraction and determination of DOX spiked in urine and various water samples, with excellent recoveries of 97.00–98.30% and 98.00–102.00%, respectively.

这项工作描述了一种基于苯扎氯铵改性二氧化硅包覆磁铁矿纳米颗粒（Fe ₃ O ₄ @SiO ₂ @BZC）的简单直接的磁性固相萃取（MSPE）方法。采用所开发的提取方法，以普鲁卡因青霉素（PP）作为显色剂衍生化后，从水和尿液样品中提取盐酸多西环素（DOX）。DOX 与显色剂在碱性介质中偶氮偶合生成最大吸收波长 ( λ _max ) 为 440 nm 的橙色偶氮染料。分析条件经过仔细优化，包括试剂和表面活性剂体积、吸附剂用量、萃取时间和溶液 pH 值。所开发的提取方法的预浓缩和富集系数分别为 47 和 25。提取步骤后，利用紫外可见光谱来确定目标分析物。 在0.08–3.00 μg/mL 的浓度范围内实现了良好的线性（R ² > 0.99）。 DOX 的检测限和定量限分别为 0.01 和 0.04 μg/mL。该方法成功应用于尿液和各种水样中添加的 DOX 的提取和测定，回收率分别为 97.00-98.30% 和 98.00-102.00%。